All of us Makers like to tinker with stuff, and in this process, we may find ourselves thinking about how to connect device A to my Arduino… Device A may operate at a different voltage from the Arduino, and may thus damage it badly….
Many different solutions exist to do this, but, many of them, like relays, can be quite bulky, increasing the overall size of your project, as well as putting bigger demands onto your power supply unit.
Having worked in the Industrial Automation sector for a few years, I remember that we used to have dedicated hardware to protect our sensitive controllers from the harsh outside signals that we needed to monitor. These devices were called isolators, and today I will show you how to construct your own version of this essential device.
But some theory is needed first…
What does it mean to isolate a signal? In the electronics world, you might have seen that you usually have to use a common ground between all your devices to make them work together properly. While this is definitely true, let us look at another example…
Let us say you have some device, that will send you a voltage signal when it switches on, and another voltage signal when it is switched off. This device runs on 24 volts, so some of the more informed of us will immediately say you need a level converter, meaning a device that changes the 24v signal into a 5v signal… Others will try to use a relay to convert the signal ( A relay is also a type of isolation device ). A much more elegant way of doing this will be by using an Optic Isolator chip.
A simple Optic Isolator Chip
This chip provides complete isolation between your device and the Arduino or other microprocessor. It does that by using infrared light to transmit the signal. Light, as we all know, does not conduct electricity 🙂
Whereas a relay will only give you a on or an off state, the Opto-coupler or Optic Isolator can also do linear current transfer, meaning that the more IR light it transmits, the more current the photo-transistor will allow to pass as well.
A good tutorial on Opto-Couplers can be found here
Opto Isolator Circuit
In my circuit, I made use of the following circuit…
Two Optic Isolator Level converter Circuits
As we can see in the two circuits above, there is no common ground between the input and output sides of the circuit. This is ideal, as noise and other undesirable signals will not be transferred from one circuit to the other. It also allows you to use a very high input voltage, at a frequency of up to 2kHz.
I have also decided to combine this with the PCF8574 I2C Port Extender. That way, I can cascade up to 64 inputs on the I2C bus. In a later version, I will also do an Opto-Isolated Output module.
The Shield is only slightly bigger than the standard Arduino Uno, and all Arduino pins are broken out on headers. It is important to remember that A4 and A5 should not be used for any other purpose (They provide access to the I2C bus). Likewise, the interrupt pin of the PCF8574 can be connected to either D2 or D3 with a jumper, or left disconnected by completely removing the jumper. Device addressing can be set with the 3-way DIP switch on the board.
8 DI Optically Isolated I2C Arduino Shield
This device is currently being manufactured. In Part 2 of this article, I will show you the completed PCB, as well as give you access to the Gerber design files if you want to manufacture your own. I will also make a limited amount of these boards available for sale from my website ( this site ) as well as from https://www.facebook.com/makeriot2020
Ai-Thinker is definitely in my opinion one of the more interesting Chinese Electronics companies out there. Most of us will be very familiar with their NodeMCU ESP8266 as well as ESP32-S modules as well as Dev boards.
They also produce the very popular Ra01 and RA02 Lora modules…
What is less known about them is that they have a very active R&D department. Over the last few months, more than 8 months to be accurate, I believe that there seems to have been quite a dramatic change happening. Many RISC-V-based chips and modules started appearing on the AI-Thinker website, and I have also been fortunate to get my hands on a few of them.
The latest of these, the AI-M61-32S, is another one of these. The chip seems to be based on the BL-616 or BL-618 from Bouffalo Labs ( No spelling error there)
Information outside of China, and in English seems to be very sparse at the moment, but it does seem like there is a lot of potential here…
Let us take a closer look at the AiPi-Eyes-S1
The board is a very neat, but dense double-layer SMD assembly, with interfaces for a touch-screen, camera, speakers and microphones as well as USB ports and a firmware flashing port.
The kit also comes with an impressive number of peripherals, including a beautiful touchscreen, a small camera, speakers and microphones.
What are my thoughts?
As stated above, I find the kit very well designed, in the sense that it looks good. The screen has very good resolution, and there seem to be enough peripherals to test out something… Why am I saying something?
1) According to the schematic, the screen and camera share GPIO pins, and can thus not function together – a definite minus point for me there. 2) There are NO free GPIO pins, and those that may be, very difficult to access – think small connectors etc 3) The demo program seems to cover some of the basic functionality of the chip, but not too much…
Let’s take a look at software support
At the time of writing, the kit has been sitting on my desk for just over 2 months. English documentation, beyond a quick guide to get the demo software running, is limited, if nonexistent.
The Touch Screen API is downloadable, but will take quite a while to decipher – It will be worthwhile though.
I have also received news from AI-Thinker that there is limited Arduino IDE support for the AI-M61-32S available. I don’t know to what extent, and will definitely explore that further in the future.
Further than that, there are links and examples for setting up some sort of API/SDK from Bouffalo Labs on the Ai-Thinker Website. Support documents seem once again to be sparse as far as English is concerned.
In conclusion
I see potential in the future for this new chip ( the AI-M61-32S ) or let’s just call it the BL-616 or BL-618 already. Ai-Thinker repackaged it into the popular ESP32-S form factor, so they seem to be hoping that it could be used as a drop-in-replacement for that.
Being RISC-V based, it is however still extremely new, and with all the various RISC-V standards currently out there, it will surely take some time to mature.
The development of an Arduino core to support it, is definitely a step into the right direction, if and only if, compatibility with existing libraries etc can be assured. That will definitely allow Makers and other hobbyists to start using the chip
As far as the AiPi-Eyes-S1 kit is concerned, well… Full marks for aesthetics – it really does look good. As far as practical use or being fit for a particular purpose goes – not so much.
The board was clearly designed as a showcase of possible uses for the AI-M61-32S only. It was clearly not meant for use as a development board.
So, would I buy one right now? a definite NO on that. In the future, yes, maybe, providing that:
1) Documentation and information are updated and made easily available. Slapping the words ” open source ” onto something does not mean that you can skimp on documentation. It is “open source” because the schematics are freely available, datasheets are available, and libraries and IDE support are available free of charge. “open source” does not mean to give someone a space shuttle, and not include the manuals, or at least a link to where to buy the manuals etc…
Over the last few months, I have been using the initial revision of this project on almost a daily basis. It has come a long way since the initial concept was implemented on the breadboard.
Initial Concept on a Breadboard
While completely functional, and relatively easy to use, quite a few things started adding up – making me believe that it could be better…
That prompted me to start thinking about a hardware revision, adding some missing features, like a middle button, and “maybe” a display to the device, making it easier to visualise settings, etc…
Current Revision 2.0 ” Proof of concept ” prototype
My main limitations came from the Seeed Studio Xiao RP2040 Module. While super tiny and compact, the module only has access to 11 GPIO pins on the RP2040 chip. Most of these were already in use, connected to buttons etc.
I would thus have to find an I2C IO expander that will be supported by CircuitPython and have a suitably small footprint. That way, I could free up many of the valuable GPIO pins on the Xiao RP2040 for other purposes.
What did I use?
My initial goto chip was the MCP23017, with 16 GPIO pins. But after some more thinking, I settled on the MCP23008, which has only 8 GPIO lines. I2C bus breakout headers to allow for expansion, as well as access to all the unused GPIO pins on the XIAO RP2040, were also added.
The Rotary encoder was once again included, as it could later be used for selecting Menu options etc.
What is the current status of the project?
The revision 2.00 hardware works as expected, with a few issues. CircuitPython has an issue with rotary encoders connected to IO expanders. I don’t understand why that would be the case, but wrote my basic routine to handle the encoder, which at this time, is only used for scrolling. ( I have still got to decide if a display would be needed)
As far as settings are concerned, I have only implemented a sort of “mouse speed” feature that determines how fast or slow ( for better accuracy ) the pointer moves. This is currently controlled by the encoder button, on a cycling loop, with different colours on the NeoPixel as visual feedback on the current speed selected.
USB connectivity at computer startup and/or resuming from a suspend operation is still a major problem. This means that you have to physically reset the device after every resume from suspend, or after starting your computer. From what I can see in the CircuitPython documentation, it is possible to detect USB connectivity. That part works. From there, It seems that once USB connectivity is lost, CircuitPython goes into some sort of unknown state, and no further code is executed, thus making a software reset not executing…
I have an idea that it has got something to do with the HID Mouse mode or something ???? For now, I am happy to just hit a reset button to continue…
Another big issue is a suitable enclosure. Revision 2.00 PCB was not designed to be placed into an enclosure, mainly because I have so far been quite unsuccessful in finding a suitable one. My 3D design skills are also quite lacking, so designing something from scratch won’t do either. I have decided to sort out all the hardware and firmware issues first, find an enclosure and then modify the PCB layout to fit that.
Manufacturing the PCB
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to who will do his/her best to resolve your issue as soon as possible.
Assembly is easy but does require a stencil due to the small size of some of the SMD components.
CircuitPython Coding – A work in progress
This is the current code, and it is a work in progress. It works, and could definitely be optimised quite a lot. I am not very familiar with Python but I believe I can help myself around it.
Okay, so this is where it is at at the moment. The code is not perfect, and the hardware is not perfect, but it works. I am using this device every day, and also making changes as needed. At the moment, there are some issues, but they do not prevent the actual use of the device.
If you are interested or would like to make modifications, feel free to do so.
I designed this breakout to assist me during prototyping my next version of the “RP2040 Emergency Mouse“. In that project, I used the SEEED Studio Xiao RP2040, along with a few other components to create a simple but effective computer mouse-type device.
While the “mouse” works quite well, I have quite early on discovered that it could be better. More on that in a follow-up article, but let us just say that I needed more GPIO pins than that were available on the XIAO RP2040 and that the layout can be improved a bit – especially If I want to get it into an enclosure.
I am still quite neutral about CircuitPython and Micropython on microcontrollers, and Python in general, but since the above-mentioned project runs completely on CircuitPython, it made a lot of good sense to get more into it.
What is on the PCB?
I wanted something as small as possible, and that meant that I chose a QFN package for the MCP23008 IO expander chip. At only 4mm x 4mm, and not being bothered to try and find a DIP version, a breakout board became a much-needed necessity.
Address Selection Jumpers, Two I2C bus headers, and of course the all-important GPIO pins make up all of the user accessible interfacing. Note that the chip reset line is permanently tied to Vcc to make things a bit less cluttered, and easier to use while prototyping.
A decoupling capacitor, as well as pullup resistors on the I2c lines, were also included. Another note here, I did not provide my usual selection jumper to disable these on this particular board.
The Schematic
Manufacturing the PCB
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.
Due to the small size of the QFN package, I strongly recommend that you either have this assembled professionally, or at least consider buying a stencil for applying the solder paste to this board. Maybe those with excellent eyesight can do without that?
Assembly took only a few minutes, with the help of an extremely accurate stencil, followed by a few minutes on a hotplate, and manually soldering on the header pins.
Using the MCP23008 with CircuitPython
I2C devices are very easy to use with the Arduino IDE or similar, and as such, I will not be covering that here.
Circuitpython, however, is gaining popularity, and I am slowly starting to see what the hype is about myself…
So, to get started, you need a microcontroller running CircuitPython – See Adafruit for excellent tutorials. You will also need a few libraries from Adafruit See this link
I will give a very simple example below, showing how to set a pin as an output, as well as an input with internal pullup resistors enabled. Note that the MCP23008 DOES NOT SUPPORT pull-down resistors internally. You need to add those by yourself externally.
# Initialising all the required libraries
import board
import busio
from digitalio import Direction
from adafruit_mcp230xx.mcp23008 import MCP23008
i2c = busio.I2C(board.SCL, board.SDA)
# Adding the MCP23008
mcp = MCP23008(i2c)
# This assumes that you are using the default address [ i.e. all address
# pins are grounded]
#
#
#
# Defining two outputs on pins 0 and 1
pin0 = mcp.get_pin(0)
pin0.direction = Direction.OUTPUT
pin1 = mcp.get_pin(1)
pin1.direction = Direction.OUTPUT
#
#
# We can now control the pins by setting them to true or false, true being
# high
pin0.value = True
pin1.value = True
#
# and switch them off again by using
pin0.value = False
pin1.value = False
#
#
# We can also use the pins as inputs.
# We will activate the internal pullup as well
#
# first , we need another library
import digitalio
pin2 = mcp.get_pin(2)
pin2.direction = digitalio.Direction.INPUT
pin2.pull = digitalio.Pull.UP
#
#
# Reading the pin value is now as easy as
pin2.value
#
# This will return True if the pin is high ( its default state with pullups # activated, of False if pulled low, by for example a switch of button )
Conclusion
The breakout works as expected, and it is very easy to use with CircuitPython. I can now continue with the actual integration and Software for the RP2040 Mouse Rev 2.0 project.
This is a modification of my existing P-MOS driver circuits, intended for use with higher current LED Lights, as well as any other applications requiring a higher current capable P-Channel Mosfet to switch a load.
What is on the PCB?
I have used the IRF4905 P-Channe Mosfet here as it can sink up to 74 Amps of current – A complete overkill in many situations. Datasheet. The Mosfet is configured in a high-side switching configuration, thus eliminating problems with ground connections.
To prevent unreliable switching, a transistor is used to switch the gate, which is normally pulled high to keep the device switched off.
I have also included various connection headers for connecting the load, Power supply, as-well-as active high control headers for controlling the driver from a microcontroller. This was especially important as the Gate voltage of the Mosfet is above the acceptable 3.3 volt for use with many of the modern microcontrollers in use today.
It is important o note that I did not yet bother to do very accurate gate current calculations. I do not need super fast switching, and on the bench, the 500mA switching capability of the S9013W transistor gave me satisfactory results.
What is my intended use for this driver?
This is a 12v Automotive Fog light. It is meant to be an aftermarket upgrade. It will also be a very nice focused working light in my workshop, as the lighting is not optimal.
My initial idea is using two of these, PWM controlled from an ESPHome-controlled device to provide me with focused, dimmable lighting for assembly and other operations where a bit of extra light will be needed.
The Fish-eye lens of the internal lamp provides a very focused beam, and from initial testing seems to be exactly what I want.
The problem came in that the LED module consumes quite a bit of current ( 5A for the center lamp, and 3A for the ring light). These currents are way above the capabilities of my existing LED COB driver circuit, thus this MOD.
The Schematic
Manufacturing the PCB
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.
This PCB is definitely quite easy to assemble, as there are only 16 SMD components on the board. These are all easily hand-solderable. The Mosfets and their respective heatsinks are through-hole components and thus super easy as well.
It is very important to note that we should NOT connect the heatsinks together. This is due to the fact that the Heatsink is connected to the DRAIN pin on the MOSFET. Connecting them together will thus short the various channels together.
For my testing procedure, I have connected the driver to the LED Fog light, as well as a 12v supply. Using an ESP8266 running ESPHome, the LED fog light was controlled with PWM. The current draw was 5A and 3A respectively. All of the MOSFETs remained cool to the touch, and the PCB tracks did not heat up as well.
Next steps
The next steps for this project would be to design a PCB that integrates this driver with the ESPHome control device, as well as design and build a suitable enclosure for the two lights and the control unit. This should ideally be mountable on the ceiling above my workbench. It would also be nice to design some sort of gimbal for each light, that can be controlled with stepper motors or servo’s to allow me to position the lights where I need them.
I use a lot of ESP32 modules in my projects, mainly because of the integrated WiFi and BT, but also due to their small size. There are however usually quite a few external components required, and sometimes, that can be a bit of a turn-off.
Having access to quite a few XIAO modules from SEEED studio, and with support for the ESP32S3 recently being added to ESPHome, my other goto for projects, I decided to create a simple prototype based on the SEEED XIAO ESP32S3. this module offers several attractive features, of which its small size is definitely a big plus. Add to that that it also has battery charging circuitry and quite a lot of flash memory, and it seemed like a winner…
Not that it doesn’t have issues of its own, the biggest being that you have to power it from 5v, and the absolutely super tiny flash and reset buttons.
Cost-wise, they are only slightly more expensive than the native ESP32 module, which, by the time you have added the external components, does not amount to any difference anymore.
I also wanted to test out some power-supply circuitry, so this seemed like a good project to combine those in as well.
What exactly is the project about?
It is a testbed for three(3) different things, with the first being the XIAO ESP32S3, with I2S sound as an ESPHome media device. That part, while working, is in my view not perfect yet, as ESPHome does not seem to be able to utilise the 8mb of PSRam available on the XIAO for use with the I2S Audio, yet anyway…
The second is having my, by now almost common, dc buck converter circuit directly on the PCB. I want to test that, in order to make sure that there are not too much noise being generated that could influence the ESP32S3, or, most importantly, the I2S module. A while ago, I built a custom I2S shield, and unfortunately, the power capabilities, or let’s be frank, the lack of sufficient power, turned that project into a big disappointment at any volume other than almost below 2%…
This will thus also serve as a way to revamp that idea, but with better power capabilities and more available current.
The third part is a direct result of the XIAO’s 5v power requirement. I reused my LM317G variable voltage circuit to provide power to the module. In my view, it would have been so much nicer if I could just supply 3v directly to the XIAO…
This also brings us to the battery charging capability. I would have loved to use that, but, 1) It seems that the battery voltage is internally stepped up to 5v and then back to 3.3v for the ESP32S3. comment anyone? 2) The available output (3.3v) does not provide a lot of current – surely not enough to drive an I2S module, does it? more comments, anyone? 3) I am unsure of any internal isolation in above mentioned charging circuit, thus, I was not willing to connect my own boost converter to the battery and use that to power external components…
So, until I get definite answers on these three, I won’t be bothering with powering the circuit from the battery… unless it is a big 12v one
So what is on the PCB?
3D Render of the PCB
As mentioned above, I had a few goals with this prototype. Let us take a quick look at the board and its components.
Starting bottom left, we have the DC input area. Here I chose to provide both a DC Barrel Jack, as well as a screw Terminal. Both can be used, but I believe the screw terminal will add a bit more flexibility in an actual installation inside an enclosure.
To the right of those, we have a 7-way header. This provides access to D7 to D10 on the XIAO, and, in my case, is labelled for use with the I2S module and a DHT11 sensor. ( you can of course use it for something else as well). The DHT11 header is on the far right in this picture.
At the centre-left, the components around U1 forms the DC-DC buck converter. This is set to supply 3.3v at a maximum current of 3A.
To the right of that, around TP1, is a jumper to that supplies the XIAO with 5v from U2 ( the LM317G ). It is important to note that you should leave this jumper disconnected at first power-up, and then adjust R9 while measuring between GND and TP1 to get a voltage of exactly 5v on TP1. This will prevent you from damaging the XIAO module. Once that is set, power down, and place a jumper on the center and right side pins. Make sure to NOT adjust R9 again with this jumper in place.
Center-right is the star of the board. The XIAO ESP32S3 Module ( marked U3) Note the cutout for the USB-C connector at its top.
A reset button, marked RST, and two headers, one for I2C and another with additional GPIO pins completes the PCB.
Note that the XIAO ESP32S3 makes use of an external antenna on a short UFL connected cable. Make sure to attach this BEFORE you power up the board for the first time.
Manufacturing
Since I have made use of a SEEED Module, I sent this to SEEED Studio for manufacturing.
Seeed Studio’s Fusion service seamlessly marries convenience with full-feature capabilities in one simple platform. Whether you are prototyping or looking for a mass production partner or based on open source product customization requirements and other design manufacturing services, Seeed Studio Fusion service is catered to your needs starting with a simple online platform. https://www.seeedstudio.com/fusion.html
Assembly and Testing
I chose to assemble this project on my own. There was some issue with component availability, and since I have most in stock myself, decided to save time and do it myself.
Little did I know that I will be severely handicapped by a broken wrist a few weeks later. That little incident forced me to use my non-dominant hand, and resulted in an almost 3-hour-long assembly operation! All did however go well, and everything works as expected.
Testing went well, and after verifying all the voltages and connections, I uploaded some previously prepared ESPHome code to the board.
Due to the fact that this is still an early prototype, as well as some issues with ESPHome, I wont be releasing the firmware just yet. That will however happen in the near future.
Imagine You are working on a project late on a Friday evening and suddenly your mouse stops working… You can not scroll, and the right-side button won’t respond to your clicks… At the same time, you have a project design that has got to get finished… and the shops are all closed already…
These were the circumstances that led to the birth of “The Emergency Mouse” – A project born out of necessity. How did I solve my problem?
Having access to a lot of electronic modules saved the day. As a maker, I always have various modules and gadgets lying around, and on this unfortunate evening, I remember that the RP2040 has USB HID support. Combine that with a simple Analog Joystick module, a rotary encoder and some push buttons, add about 30 minutes worth of browsing the internet, struggling along with a broken mouse – we have to give the old one credit, it had a very long and hard life, and I finally found some example code that did not just jiggle the mouse pointer or do something equally silly…
The only problem with all of that was that the code was for CircuitPython… I generally dislike using Python on a Microcontroller, as I believe it is better suited for the computer, but, I am warming up to the idea… slowly…
The initial fix – a mess of wires on a breadboard
I quickly grabbed a RaspBerry Pi Pico out of a box, plugged it into a breadboard, loaded Circuitpyth and fired up the example code I got on the internet… While promising, It did not exactly do what I wanted… so a few minutes later, after some coding, I had a moving pointer, controlled by the small thumb joystick module, and with the center button as a “right button”…
So far so good… I can work more easily, but still did not have scrolling… so lets hit the datasheets and documentation on the Adafruit Website (not sponsored) and add a rotary encoder… works well, add more buttons, etc etc…
Eventually it was all done, and about 1 hour has passed, but we were left with a huge ugly mess on a breadboard, and a lot of unused GPIO pins.. So this Pico must go… it can be used for something more useful later…
Then my eye fell on a SEEED Studio XIAO RP2040 module, almost begging to be used… This is smaller, more compact… lets try that …
Initial breadboard version, here shown with the SEEED Studio XIAO RP2040
What functions did this “mouse” have
After changing to the XIAO RP2040, things went very quick…
I added two buttons for scrolling up and down, simulating a mouse wheel, but kept the encoder… which, while VERY awkward to use at this stage, definitely had potential in the long run…
I also added another button to take over the function of a right button, while the center button on the joystick became left…
Disaster averted, with only about 2 hours wasted, I returned to my project and managed to get it finished using the “improvised-mouse-on-the-breadboard” contraption…
That night, while lying in bed, trying to get to fall asleep, the possibilities of this “contraption-on-the-breadboard” would not let me go… I am fairly old-school, and during the late 80’s and early 90’s owned quite a few “roller-ball” mouse devices… these later became trackballs, and being excessively overpriced, was promptly removed from my environment – the old ones did not last very long, and the new ones were, as I said, overly expensive…
I did however never forget the ease of use that first “rollerball mouse” gave me all that years ago, using only my thumb to move it around etc etc…
This idea would have to be investigated, and turned into a PCB… with that, I finally drifted off to sleep…
The PCB design
The next morning came, and due to reasons unknown, as well as being lazy, I decided not to leave the house, and go buy a new mouse. lets try online… No, they are crazy – I am not paying that for a mouse!
All the time using the “contraption-on-the-breadboard”. So this thing started growing on me… lets design a PCB
The Initial PCB design
After a few hours spent on deciding on optimal layout, I came up with this… It was still a bit unrefined, but definitely had potential… It lacked a dedicated center button, and those momentary push-buttons requires a lot of force to use… but as a prototype, why not…
Let’s get this manufactured.
For this build, since I used a SEEED Studio module, I decided to send it to SEEED for manufacturing… no need to get components from various places, as they should have all in stock…
Seeed Studio’s Fusion service seamlessly marries convenience with full-feature capabilities in one simple platform. Whether you are prototyping or looking for a mass production partner or based on open source product customization requirements and other design manufacturing services, Seeed Studio Fusion service is catered to your needs starting with a simple online platform. https://www.seeedstudio.com/fusion.html
The PCB arrives from the factory
During the entire time that it took for the PCB to be manufactured and assembled, I was still using this “homemade mouse” – I started calling it a mouse now… and it was still on the breadboard… I never did bother to buy a new mouse, yet..
The PCB Arrived today, and apart from a few small soldering issues, looked great… I still had to do a bit of assembly on my own, as there was an issue with the components I wanted being out of stock.. I have plenty in stock of my own, so opted to do manual assembly…
The completed PCB now only needed a joystick, and some firmware…
After adding a few button caps, and mounting everything to a piece of acrylic plate, I had a working prototype…
The Firmware
As mentioned above, the device runs on CircuitPyton. As Such, there are quite a lot of “examples” on the internet, showing you how to do many USB HID “mouse” like things, but generally being completely useless…
I have thus spent quite a lot of time up to now, writing and refining my own version of the firmware, that is actually useful and does actually work.
It has the following features: X-Y axis control of the mouse pointer via a thumb joystick, with a left click function on the center joystick button, as well as a dedicated “left” button.
A dedicated “right” button A “virtual center” button made up of simultaneously pressing left and right
Up and down scrolling either using the rotary encoder as a “mouse wheel” or via dedicated up and down pushbuttons.
A dedicated Reset button – this is necessary, as I can not seem to get the device to initialise correctly at computer bootup.
Various software functions, like changing the pointer acceleration by pressing the center button on the rotary encoder
and most importantly, hiding the Circuitpyton drive, only showing it when I actually need access to the code in this device…
Various statuses are indicated using the NeoPixel on the XIAO, making it easy to see in what state the device is operating.
As such, I shall NOT be releasing the firmware at this moment, as it is still far from being perfect. It works, but it can be way better…
Summary and next steps
Since its “birth” late on a Friday night, about 3 weeks ago, I have been using this device, in its various forms as my primary pointer device. It is growing on me more every day, and it is quite comfortable to use – If we ignore the fact that it is not in a suitable enclosure and that I am still making small changes to the firmware from time to time.
I am already planning the next revision, in which I shall replace the momentary push-buttons with proper microswitches, as well as try my hand at designing a proper enclosure.
If you are a 3D printing expert and want to collaborate with me on this, let’s talk…
When we are working on a prototype, we always need access to pushbuttons, encoders and even displays to test our ideas in the real world. This Multi-Purpose IO Card was designed to help me do just that…
What is on the PCB?
This PCB was designed with my particular work style in mind. I use a lot of I2C devices, IO Expanders, Displays and sensors. It would thus make sense to have I2C on the PCB, to control an OLED display, as well as a PCF8574 IO expander, that is used to drive a 4×4 Matrix Keypad. Two Rotary encoders, as well as another 4 standard push buttons completes the PCB…
The features, summarised is as follows:
1x Matrix Keypad (4×4) Controlled via an PCF8574 IO expander with selectable addressing. 1x SSD1306 OLED I2C Display 4x Momentary pushbuttons, configured to be used with internal pullups – i.e pushing the button pulls the GPIO LOW 2x Rotary Encoders, with integrated Pushbutton, also configured as Active LOW
The board has all of the connectors and jumpers on the back, making it possible to mount it to an enclosure as a control panel.
I have also provided an additional I2C header to make it possible to add additional devices to the I2C bus easily
The PCB in Detail
PCB Top
Starting from left to right, we have two push-buttons, an OLED display, with two rotary encoders below the display, and another two momentary push buttons. On the Right, we have a 4×4 matrix keypad, and various pin headers for connection to a microcontroller of your choice.
On the back, we have the PCF8574 IO expander for the Matric keypad, addressing Jumpers for the IO expander, as well as the two pin headers for connections to and from a microcontroller…
The Pinouts of these are as follows: Horizontal 15 pin 2.54mm connector SDA I2C Data SCA I2C Clock
RE2-D Rotary Encoder 2 Push Button RE2-B Rotary Encoder 2 Pin B RE2-A Rotary Encoder 2 Pin A
RE1-D Rotary Encoder 1 Push Button RE1-B Rotary Encoder 1 Pin B RE1-A Rotary Encoder 1 Pin A
GND VCC 3.3v to 5v DC
The Expansion header extends the I2C Bus, as well as proved access to the interrupt pin on the PCF8574. VCC and GND are also provided.
The Schematic
Manufacturing the PCB
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.
The assembly of this PCB was relatively easy, as it contains only a single SMD component. I do however have to alert you to a certain caveat…
On the PCB, the I2C OLED display pinout is, from left to right,
VCC GND SDC SDA
I have however come across similar displays that swap the GND and VCC pins… and some that even have SCL and SDA swapped…
It is thus quite important that you check your display BEFORE soldering it to this PCB…
Addressing the PCF8574 is also quite easy, with the jumper towards the top is a high, and towards the bottom is a low… They are marked A2 A1 A0 and thus, counting in binary, all low will be 0x20h and all high will be ox27h
Also, note that there are NO I2C Pullup resistors on the board. My microcontroller PCB’s usually have these already, and most I2C Sensors, including the OLED Display that we use, already include as well… You should thus check what you have on your own hardware, as it is quite impossible to cater for every situation… In a future version, I may add selectable pullup resistors onto this board as well…
Coding and Firmware
The possible uses of this board is quite broad, and the code possibilities are thus also quite extensive. Since I mainly use ESPHome or the Arduino IDE with most of my projects, I wont be including any specialised code here. I think it is enough to say that almost all of the available PCF8574 Matrix Keypad libraries available for the Arduino IDE will fork with this board…
The pinouts are important, and thus :
Row 0 – P0 Row 1 – P1 Row 2 – P2 Row 4 – P3
Col 0 – P7 Col 1 – P6 Col 2 – P5 Col 3 – P4
As far as ESPHome goes, you will need to 1) Add an I2c bus for your device 2)Add a PCF8574 component 3)Add a Matrix Keypad component, and refer the rows and columns to the pins on the PCF8574 – See below for an example of how I have done that in a previous project.
#I2C bus
i2c:
sda: 4
scl: 5
scan: true
id: I2C_Bus
#
# In my case, SDA is on GPIO4 and SCL is on GPIO5
# This is similar to the standard configuration on a NodeMCU v2 Dev board
#
#
# The next step is to configure the actual IO Expander, which in my case is located
# at address 0x27
#
#PCF8574
pcf8574:
- id: 'pcf8574_hub'
address: 0x27
pcf8575: false
#
# Now we can add the actual keypad interface to the YAML file
# Take note of the difference from the ESP32 file above.
#
#
#KEYPAD
matrix_keypad:
id: mykeypad
rows:
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 0
# In the ESP32 file, we wHereould specify a pin directly like:
#
# -pin: 17
#
# That approach will not work for us.
# The reason for that is that we have to redirect the GPIO to a
# physical pin on the PCF8574 IO expander.
#
# That is done with the following syntax
#
# - pin:
#pcf8574: pcf8574_hub -- This is the ID of the PCF8574 device -
#number: 0 -- The actual pin number
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 1
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 2
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 3
columns:
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 7
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 6
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 5
- pin:
pcf8574: pcf8574_hub
# Use pin number 0
number: 4
keys: "123A456B789C*0#D"
has_diodes: false
The Rotary encoders and momentary push-buttons can be handled in the same manner, using standard libraries in the Arduino IDE, or a rotary encoder component in ESPHome…
The OLED display would also be handled as above, with a DISPLAY component in ESPHome…
Summary and next steps
The next steps, for me at least, would be to design and CNC cut a suitable enclosure for the IO panel/Control panel in order to make it easier to use…
The panel was designed to be a tool to aid me while designing, and part of my never-ending battle getting rid of breadboards.
It does its job well, at least so far, and works as I have intended it to.
Adding a bit of automation to a certain area of the house can definitely help with saving energy. With this Simple Smart Light Controller, I aimed to do just that… Let me give you a tiny bit of context… Houses in SE Asia are built to some “questionable” standards and designs, and electrical installations are usually even more suspect… Our house is no exception. Being a rental, I do not want to go and make changes unless things are outright dangerous… Kitchens are usually a mixture of inside/outside areas, and this is where my device fits in…
The light in the outside kitchen consists of a simple bulb that the owner has routed into the house via an electrical flex cord, at least that was standard… But, due to laziness or just whatever, that cord was never terminated into a proper switch… He just added a plug. This is thus my opportunity to make life a bit easier for myself in that area. I could have opted for a standard switch, but then, automating this can take care of another problem… We constantly forget to switch that light off, as the plug is in a “strange place” that is not usually associated with the kitchen lights…
What I have thus come up with is a simple ESP8266-based solution with a single relay ( optically isolated from the board), as well as a few additional GPIO pins, just in case I want to hang some additional sensors onto this in the future.
The device should also be powered directly from the mains, as adding another external AC to DC adapter would definitely NOT do at all!
What is on the PCB
Lets look at the empty PCB, in order to understand better what is where on the board.
Starting on the Left Side, at the bottom corner, we have our mains voltage input, 220V or 110V, depending on where you live. That goes directly into U1, which is a AC-to-DC converter, providing 3.3v at 1A to the board. Note that I did not place a fuse directly on the board. I prefer to have an inline fuse on the line, which is also accessible from the enclosure.
A series of cutouts on the PCB provides additional mains isolation and also prevents mains voltage tracking towards other tracks in the event of a fault. The Mains area also does not have a copper pour.
In the top left corner, towards the center, is a WAKE jumper. This is connected to GPIO16 and can be used to wake the ESP8266 from “deep sleep” if configured in the firmware.
Relay K1, and its screw terminal connector is in the bottom center of the board, with the relay contacts clearly labelled.
On the right of the PCB, we have the programming header, complete with Auto Flash and Reset circuitry, as well as manual Flash and Reset Buttons below that.
A 3×3 header connector follows, with access to 3.3v, Ground as well as 3 additional GPIO pins for other applications.
Finally, we have the relay control switch, with a few options to connect external switches, either on the 2.54mm header, or via wires soldered to the pads marked SW-A and SW-B
The populated PCB will thus make more sense if we look at the picture above now since we had a detailed look at it above…
The Schematic is made available at the link above.
Configuration and Software
This build was designed with ESPHome in mind, so we will focus on that there. You can however very easily use standard Arduino/ESP8266 code to control this as well…
The YAML configuration for the device will be as follows: (note that this is quite simplified, as I am still fine-tuning the actual features that I require)
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.
This device does not need a stencil for assembly, but using one will definitely speed up things. I chose to do this build all by hand, from applying solder-paste, up to placing components.
Soldering was done on a hotplate, as usual, to reflow everything at the same time. TH components were then placed and hand-soldered.
Uploading the initial firmware, after adding the device to ESPHome was done with an external USB-to-UART converter. All further firmware changes were made via OTA.
Enclosure and some of the wiring
It is important to mention here that this PCB is powered by mains voltage. I chose to use an inline fuse, BEFORE the connector on the PCB. It is also notable that the relay common is connected to the live wire, BEFORE the fuse, as the lightbulb acts as its own fuse – it blows when a fault occurs.
The Lightbulb neutral will be connected to the circuit breaker, together with the device live and neutral.
This way, the fuse only acts on the actual device, and I can use a lower-rating fuse, since I do not have to accommodate the current from the lightbulb as well…
Summary
The device works as planned, with no problems… Below is some pictures from it in Home Assistant
COB LED lights, or Chip-on-Board LED lights, are a type of LED light that has all of the LED chips mounted on a single substrate. This makes them more efficient than traditional LED lights, which have individual LED chips mounted on a circuit board. COB LED lights also produce a more uniform light output, and they can be used in a wider variety of applications.
Here are some of the benefits of using LED COB lights:
are very efficient, and they can produce up to 100 lumens per watt. This means that they use less energy than traditional light bulbs, and they can save you money on your energy bills.
produce a more uniform light output than traditional LED lights. This means that they do not create hot spots or shadows, and they provide a more comfortable light to work under.
are very durable, and they can last for many years. They are not as susceptible to damage from heat or vibration as traditional light bulbs, and they can withstand harsh conditions.
can be used in a wide variety of applications, including indoor and outdoor lighting, commercial and residential lighting, and automotive lighting.
They can however be quite a pain to power in a traditional 110v/220v AC wired house or workshop, as some of them actually required DC current to work. I have decided to use a pair of them to provide additional, dimmable light at my electronics workbench, a place where extra light is sometimes a very necessary commodity. The ability to dim the lights will definitely aid in many scenarios as well.
The Variable voltage Power module was designed specifically for this project
The project consists of two main parts, the first being the Variable Voltage Power Module, which I published a few days ago. The particular COB lights that I will be using, were scavenged from a battery-operated emergency light panel, which had some problems which were not economical to repair. The light modules themselves, however, looked good and were perfectly working as well. The only issue was that they were 6v DC. So using straight 12v there was out of the question. 6V being an odd voltage in my lab, I designed the module above specifically to provide that.
LED COB Controller stacked on top of Variable Voltage Poser Module
The second part of the project consists of a simple Custom ESP-12E PCB. Why ESP12-E? Well, I have a lot of them lying in stock, and since I won’t need any advanced features, commonly found on the bigger ESP32s, I decided to design around something that I have in stock, rather than overcomplicate the design with a bigger more advanced chip. The project features a rotary encoder, to adjust light intensity, as well as push buttons to toggle the lights on or off…
All of this is of course controlled with ESPHome. This choice gives me the option of manual or fully automatic control from HomeAssistant. It also saves me a lot of coding, as everything usually just works.
What is on the PCB?
We shall focus mainly on LED COB Controller PCB. In order to understand everything, please refer to the picture below:
LED COB controller without Power Module
The board consists of a few sections, which can be divided as follows:
ESP-12E (8266) supporting circuitry
The top area is mainly the supporting circuitry for the ESP-12E, which includes a 6-pin header to flash firmware, the classic ESP32/8266 Auto Flash/Reset circuit, and manual Flash and Reset switches. Note that the board DOES NOT contain any USB-to-Serial circuitry. I usually use those only once or twice, and update firmware OTA after that. Using an external USB-to-Serial adapter is thus sufficient for my purposes.
Power and LED Control circuitry
Power enters the board in the center, using header pins mounted on the bottom of the PCB. From left to right, these are 3.3v and then two variable voltage inputs. These all originate from the Variable voltage Power Module, mounted below the main PCB. The LED Control circuitry consists of two P-Channel Mosfets, the configuration of which was previously tested in another project, the “P-MOS MOSFET Driver Board“, also published a few weeks ago. The SI2301 P-Channel Logic Level MOSFET, used here is capable of switching up to 2.3A at 20v, and thus more than capable of handling the 300mA that the LED COB modules require.
Four cutouts are provided to access test points on the power module below, as well as the potentiometers used to set the voltage that will ultimately be sent to the LED COB Modules.
Wide copper traces connect the Mosfet’s to Screw Terminals for the LED Modules.
The Final part of the PCB is dedicated to control interfaces. A single 6-way screw terminal is provided at the bottom left corner, this is used to connect a rotary encoder, or give direct access to additional GPIO pins. On the Right hand side of the PCB, a series of header pins give access to additional 3.3v and ground connections, in addition to GPIO 4 and 5, which is usually used for I2C…
LED COB Controller stacked on top of Variable Voltage Poser Module
The Schematic
Configuration and Software
As mentioned above, this device was designed to be used with ESPHome. The configuration is thus a single YAML file and can be greatly customised to suit your exact needs…
With that in mind, I present here a VERY basic YAML file, that will toggle the LED lights on or off on pressing the encoder switch, as well as adjust the brightness by turning the encoder.
esphome:
name: led-cob-controller
friendly_name: LED_COB-Controller
esp8266:
board: nodemcuv2
restore_from_flash: True
# Enable logging
logger:
# Enable Home Assistant API
api:
encryption:
key: "<esphome generated>"
ota:
password: "<esphome generated>"
wifi:
ssid: !secret wifi_ssid
password: !secret wifi_password
# Enable fallback hotspot (captive portal) in case wifi connection fails
ap:
ssid: "Led-Cob-Controller"
password: "<your recovery password here>"
captive_portal:
# I suggest you only copy paste from here on downwards.
# Setup the default device in ESPHome, and when it is available,
# come back and add the commands below here
text_sensor:
- platform: wifi_info
ip_address:
name: IP Address
ssid:
name: SSID
bssid:
name: BSSID
mac_address:
name: Wifi MAC
scan_results:
name: WiFi Scan Results
sensor:
- platform: adc
pin: VCC
name: "ESP8266 Chip Voltage"
id: mcu_voltage
unit_of_measurement: "V"
device_class: "voltage"
accuracy_decimals: 2
update_interval: 60s
entity_category: "diagnostic"
- platform: wifi_signal
name: "WiFi Signal Sensor"
id: wifi_strength
device_class: "signal_strength"
unit_of_measurement: "dBm"
update_interval: 240s
entity_category: "diagnostic"
- platform: copy # Reports the WiFi signal strength in %
source_id: wifi_strength
name: "WiFi Signal Strength"
filters:
- lambda: return min(max(2 * (x + 100.0), 0.0), 100.0);
unit_of_measurement: "%"
entity_category: "diagnostic"
- platform: copy
source_id: rcbright
name: "LED Light Brightness"
unit_of_measurement: "%"
filters:
- lambda: return (x * 100);
- platform: rotary_encoder
name: "Brightness Control"
id: rcbright
min_value: 0.00
max_value: 100.00
publish_initial_value: True
restore_mode: RESTORE_DEFAULT_ZERO
pin_a:
number: GPIO13
inverted: True
mode:
input: True
pullup: True
pin_b:
number: GPIO2
inverted: True
mode:
input: True
pullup: True
resolution: 1
accuracy_decimals: 2
filters:
- lambda: return x / 100 ;
on_clockwise:
- light.control:
id: led_light1
brightness: !lambda |-
// output value must be in range 0 - 1.0
return id(rcbright).state ; // /100.0;
- light.control:
id: led_light2
brightness: !lambda |-
// output value must be in range 0 - 1.0
return id(rcbright).state ; // /100.0;
on_anticlockwise:
- light.control:
id: led_light1
brightness: !lambda |-
return id(rcbright).state ;
- light.control:
id: led_light2
brightness: !lambda |-
// output value must be in range 0 - 1.0
return id(rcbright).state ; // /100.0;
binary_sensor:
- platform: gpio
pin: GPIO14
id: light_switch
name: "Light Switch"
device_class: light
on_click:
then:
- light.toggle: led_light1
- light.toggle: led_light2
light:
- platform: monochromatic
name: "LED1_LIGHT_TEST"
id: led_light1
output: output_component1
- platform: monochromatic
name: "LED2_LIGHT_TEST"
id: led_light2
output: output_component2
# Example output entry
output:
- platform: esp8266_pwm
id: output_component1
pin: GPIO12
- platform: esp8266_pwm
id: output_component2
pin: GPIO16
Manufacturing the PCB
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.
This device does not need a stencil for assembly, but using one will definitely speed up things. I chose to do this build all by hand, from applying solder-paste, up to placing components.
Soldering was done on a hotplate, as usual, to reflow everything at the same time. TH components were then placed and hand-soldered.
Uploading the initial firmware, after adding the device to ESPHome was done with an external USB-to-UART converter. All further firmware changes were made via OTA.
The board performs well, with only slight heating of the LM317G variable voltage regulators on the power module when both LED COB modules are at 100% brightness. The current draw is within limits and seems to peak at about 600mA per COB…
Conclusion
This project took quite a while to move from idea to practical reality, mainly due to being busy with other more important stuff. In the end, I am happy that I sat down and did it, because it definitely will become a valuable tool in my work area.
Powering electronics projects are always challenging. This Variable voltage Power Module was designed to solve such a problem for a specific project that I am working on.
The ESP32 and their smaller cousin the ESP8266 are pretty well known for their high power requirements. Having used quite a few of these in various projects over the years, I wanted a power module that can supply me with enough current to keep these hungry little chips satisfied. I also needed variable voltages with more modest current capabilities, to drive LED COB modules for example.
The idea thus came to me to combine two recent projects, that I have been using together on the bench with great effect. These two are the Variable Breadboard Power Module, based on the LM317G, and the DC-DC Buck Converter that I designed a short time ago. Between these two devices, I can deliver up to 3A at 3v or 5v, or a variable voltage at up to 1.5A.
Let us take a look at what exactly was done here.
Variable Power Module
What is on the PCB?
The PCB consists of 3 independent power circuits, the first of which is a DC-to-DC Buck module, based on the MP9943 from MPS. This chip can source up to 3A at a preset voltage. In my case, I chose 3.3v and 5v, as I use those the most.
The second and third parts are a mirrored section, with the humble LM317G at their hearts. These are set up as variable voltage regulators, with their outputs adjustable via R10 and R13. These two can source two independent voltages, from about 1.0v right up to about 11.5v ( if VCC is 12V) at a respectable 1.5A or current.
All of this is powered by a single 12v Power supply. Note that the 12v supply should be capable of sourcing at least 3A of its own…
The stepped-down voltages are provided via 3 2-way headers at the top of the PCB.
How do you use the board?
Using the module is easy. Power it from 12v DC ( or up to 24v if you really want to)
The 3.3v or 5v output is selected using jumper J1 ( Please switch the power off first, BEFORE you change this). The selected voltage will be available at H1
H2 and H3 provide variable voltages, that can be set using R10 for H2 and R13 for H3. Turning the potentiometer anti-clockwise will reduce the voltage, clockwise to increase.
Test points ( TP1 and TP2) can be probed with a multimeter while adjusting the voltages.
The Schematic
Manufacturing the PCB
I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?
PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.
How do they do that?
PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.
PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.
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This PCB uses some very tiny components, so a stencil is highly recommended.
The Buck Converter IC is especially tiny.
Most of the other components can be soldered by hand, but I chose to do the entire assembly on a hotplate to reflow everything at the same time.
Testing
Variable Power Module
After assembly, I tested everything, measuring voltages with a multimeter, as well as adjusted H2 and H3 down to 6v, as I would be using the module on another project. I also tested the ripple on the Buck converter with an Oscilloscope, and it was well within the specs stated by the datasheet, at about +/- 100mV.
The entire module draws about 650mA at no load, and up to 3A when powering 2 6v LED COB modules and an ESP32 with I2S Audio modules connected as well. Most of the current actually being drawn by the LM317G chips. The Buck converter is actually quite economical, drawing a modest 500mA at full load ( tested with a separate module that only contains a single buck converter module).
Conclusion
The power module works exactly as expected. It will perform well for its intended purpose, i.e powering an ESP12-E (8266) ESPHome device with two 6v LED COB modules in PWM mode, as well as an I2C display and various other sensors. In that application, I have successfully tested the entire project with a modest 12v at 1A wall-brick transformer, with no overheating or power shortage on any of the components. That is thus a win, in my books at least.
