August, 2022 - Maker and IOT Ideas

USB Power Supply Module

USB Ports are quite handy to power all our day-to-day electronic devices, but most charging devices are limited to a single port. While it is possible to get a commercial multi-port USB-Charger ( I have quite a few myself), they are usually limited in charging current or very cheaply made.

I decided to do my own, at this time limited to supplying power only, but with a few added features to make it my own.

Features

Individual switching of ports
Individual power LED indicator on each port, that can be left disconnected for total dark operation ( I don’t like charging lights in the bedroom )
Switchmode Power Supply unit, up to 2A output
Wide input supply options, not limited to 5v
Wide power tracks to ensure decent current transfer, and reduce heat generation on the PCB

Why did I choose to build my own?

We use USB ports on almost all our electronics devices, and most of the charging units that comes with these are quite badly designed. They are underpowered, have only one port, and have annoying lights that are quite bright at night.

I wanted a single unit that can accept up to 4 devices, control each port individually, as well as be relatively small and compact for travel use.

The PCB

The PCB is a double layer, with wide power tracks on opposite sides of the board. The component count is quite low, with only USB3 Type Female connectors(4), a single MP1584 Buck converter module, 4x current limiting resistors for the LED indicators, as well as male header pins for the switches and LED indicators.

The biggest challenge was to get the port spacing correct so that it will be easy to use all of them at the same time. CNC cutting the enclosure should also not be too difficult as well, once I get around to designing that in CAD/CAM

The Schematic

I have chosen to keep it simple on this revision, and only supply power via the ports. I plan to maybe do a full data-capable USB 3.0/ USB3.1 Hub later.

Manufacturing

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An SMD Breadboard

The electronics Breadboard is definitely one of those things that electronics hobbyists use quite a lot. It allows you to prototype your design relatively easily, with the use of breakout modules, wires and leaded components.

While this seems like a good thing, these breadboards are also unfortunately not perfect. The wires and connectors add electrical noise, and stray capacitance, as well as a certain level of unreliability.

My biggest issue with breadboards is not that though. it is the fact that you can only use through-hole components. Breakout PCBs is sort of a middle ground, as they allow you to connect SMD chips to stuff on a breadboard with wires, but that is not the issue here.

Doing a lot of prototyping, having a lot of components lying around, and then having to still try and find TH versions of everything to prototype with becomes costly in terms of time and space. If you have a larger project, but you are not yet at a stage to have a PCB made, adding another breadboard to the already cluttered setup is sometimes quite a challenge.

To get rid of this major point of frustration to me, I decided to try to solve it for myself by designing a SMD breadboard Hybrid.

What is on the board?

Quick Specifications

-300-hole solderable breadboard (dual layer, plated through-hole pads)
-64 0805 SMD pads, with plated through hole pads for connectors
-8 BJT/Mosfet footprint pads (SOT233/SOD23-3) with 3 plated through-hole pads per terminal
– 3 Power rails, 30 holes each for Vcc and Ground (Common ground on all)
– Mesh-style ground plane on both sides of the PCB.
– 4 mounting holes

Details

To address all of the various issues that I have with breadboarding, I did the following:

I hardly ever use more than a 300-hole breadboard for single stage of a project.
Many of these circuit blocks could benefit from being a permanent soldered solution, but does not warrant the time and expense to design a dedicated PCB to hold them.

The first thing to do was thus to design a 300-hole PCB breadboard, complete with top and bottom power rails.

My next issue was SMD components. Chips have many footprints, and to try and design for each of them would turn into a nightmare. Breakout PCB’s would thus still be used for those. My biggest issue was BJT’s Mosfets Capacitors, diodes and resistors.

These can be bought in lead versions, but that was exactly what I tried to get away from, so it needed some thinking.

Resistors, capacitors and diodes have only two terminals, and could thus easily be soldered onto 0805 resistor pads (depending of course on the capacitor size )

BJTs and Mosfets need their own footprint.

Each of the SMD components has a corresponding through-hole pad, to easily connect it to a different part of the board as needed. BJT’s and Mosfets have 3 per leg.

Hopefully this will make things a bit more organised in future, and save me some time;

Manufacturing

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ATMega328 I2C Base Board

In this planned to be a short post, I will quickly take a look at a scaled-down version of the ESP-12E I2C Base Board. This one in particular has only two slots, without the dedicated ESP-Card slot.

The main reason for this PCB is that the original version was designed for easy prototyping and projects where enclosure space will not be an issue. This is especially true in the case of the actual project that this will be used in, as there are quite a lot of other, very bulky components, that all need to be fitted into a relatively small enclosure.

What is on the Board?

The board contains two 2×20 Pin Male Header slots, providing 12v, 3v, Ground and access to the I2C bus, as well as additional GPIO’s as provided by the module plugged into the slot. I have also decided to provide breakout access to these IO’s on the actual PCB.

This is a feature that was not yet implemented on the original prototype.
Additional Ground connections, as well as an I2C expansion port, used to interconnect to other Base Card modules were also added.

It is also important to note that the I2C bus is powered by 3v. Interface modules should take this into consideration ( mine does ).

Power is provided by an MP1584 Buck converter module.

What has Atmega328p to do with it?

I called it ATMega I2C Base Module due to the fact that I plan to design a custom ATmega328P prototype card specifically for this unit, with all possible IOs broken out to header pins. I found that this style of prototyping suits my development cycle quite well, as I really dislike using breadboards and wires.

As I try to reuse a certain PCB or design it to be as general purpose as possible, having access to ready-made modules that can be slotted into a base and programmed, really saves a lot of time.

Schematic

Schematic_Atmega-Card-Base_2022-08-25 Download

Manufacturing

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PWM Controller with R/E

Last month I spent quite a lot of time on expansion modules for use with the ESP-12E I2C Base Card. While the system worked exceptionally well as a prototyping and firmware testing platform ( as originally intended ), I immediately saw that the physical size of everything ( base board, with the cards) would be a problem inside any enclosure, when used with a real-world project.

At the same time, I have an ongoing need to design and manufacture a device for a friend, that will have very limited space inside the enclosure due to other essential components.

I have thus decided to combine the functionality of two of the IO Expander cards into a more compact design, on a single PCB ( Which I plan to use to power and control an Air Assist blower on my desktop CNC/Laser cutter, as well as function as a next step prototype for my other project.

The PCB

Let us take a quick look at the PCB.

Starting from the top left, we have the Blower/Fan Header.
This supplies 12v DC to the Blower/Fan motor, as well as the PWM signal to control the speed. ( Level converted up from 5v DC to 12V, and then reduced to 3.3v ) This may seem strange.

Let me explain for some more clarity…
The PWM input on the Blower/Fan is internally pulled HIGH to 12v ( by the motor driver circuitry – I can not change that, as it is a commercial unit.) The datasheet however calls for a 0v to 3.3v PWM signal to control the speed.

There is also a further input from the fan, which is a pulsed speed indicator (Fan RPM). This signal is 5v.

Next to that header, is a UART Header, with Rx, Tx and DTR signals, with a ground. I do no longer add USB-to-UART chips to my designs because they are not used a lot, take up unnecessary space, and I tend to program with ICSP anyway.

On the right of that, (Red/Blue/Yellow Header) are 5v, Gnd and 6 Analog inputs(A0-A3, A6,A7) [A4 and A5 being used for I2C]

The ICSP programming header is below that,
with a jumper to select PCF8574 interrupt on Pin D2 or not

This is followed by 6 GPIO (P2-P7) from the IO Expander, and
additional GPIO (D10, D11, D12, D13) , as well as (D7,D8,D9) [To be used with a Rotary Encoder]

Another 6way Ground header, as well as the 12v input (red), follows.

Finally, we have J1 and J2, which will switch 12v through BSS138 Mosfets to control static speed 12v cooling Fans (Only one of these is PWM capable)

The 2 Relays are optically isolated from the controller and mains isolation cutouts are provided to further keep DC and AC voltages well away from each other. [ they really don’t play well together, don’t they ?]

This wraps up the quick PCB description.

Schematic

The Schematic is below, along with a download link ( zip format, with PNG image files)

Schematic_PWM-Fan-Controller-with-RE_2022-08-19 Download

Some more pictures

I use stencils with almost all of my SMD assembly. It saves a lot of time, makes for even solder paste application, and prevents the mess associated with applying solder paste with a syringe, or even worse a skewer-stick or something similar. They do cost extra though, but I find it well worthwhile in comparison to the mess and time that they save.

Manufacturing

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Using a Rotary Encoder

As part of an ongoing project, I recently designed an expander card for my ESP-12E I2C Base. I am referring to this device( Atmega 328P Base PWM Controller Card). At the time of writing that article, I have not released any of the code for the project. This is a very short post, showing one possible way to implement a rotary encoder onto that particular device. (It can also be adapted for other devices, of course)

Arduino Style Code for using a rotary encoder

// Constants and Variables
const int encFWD = 8;
const int encREV = 7;
int aState;
int aLastState;
int encDir;
int encTurned = LOW;
int encLastState;
int encValue = 0;
int lastEncValue;
const int encInc = 10;

unsigned long lastEncDebounce = 0;
unsigned encDebounceDelay = 50;
const int encBtn = 9;
int encButtonState;
int lastEncBtnState = LOW;
int EncBtnValue = LOW;
int encBtnState;

void setup() {
  //Rotary Encoder
  pinMode(encFWD,INPUT_PULLUP);
  pinMode(encREV,INPUT_PULLUP);
  pinMode(encBtn,INPUT_PULLUP);
  // Init the pins in UNPUT Pullup Mode
  encTurned = LOW; // Flag for encoder

  encLastState = digitalRead(encFWD);
  //Serial
  Serial.begin(115200);
  //Status LED on D13
  pinMode(13,OUTPUT);
  digitalWrite(13,LOW);
}

void loop() {
  lastEncValue = encValue;
 //Handle the Encoder Push Button
 encBtnState = digitalRead(encBtn);
 if (encBtnState != lastEncBtnState) {
    lastEncDebounce = millis();
 }
 if ((millis() - lastEncDebounce) > encDebounceDelay) {
    if (encBtnState != encButtonState) {
        encButtonState = encBtnState;
        if (lastEncBtnState == LOW) {
          EncBtnValue = !EncBtnValue; // Toggle the button Value
        }
    }
 }
 lastEncBtnState = encBtnState;
 // Handle the Rotary Encoder Dial
 aState = digitalRead(encFWD);
 if (aState != aLastState) {
    if (digitalRead(encREV) != aState) {
       if (encTurned == LOW) {
          encLastState = encTurned;
          encTurned = HIGH; // Set Flag
// Setting this flag will get rid of double value entries caused by contact
// bounce inside the encoder. I found it easier to implement this way
// as opposed to using software debouncing as with the button

       } else {
          encTurned = LOW; // Set Flag low
// This will ensure that the value is increased only once per "click"
       }
       if ((encValue < 300) && (encDir == 0)){
          if ((encLastState == LOW) && (encTurned == HIGH)){
            encValue = encValue + encInc;
            encDir = 1;
          }
       }
      
    } else {
      if (encTurned == LOW) {
        encLastState = encTurned;
        encTurned = HIGH;  
      } else {
        encTurned = LOW;
      }
      if ((encValue > 0) && (encDir == 0)){
          if ((encLastState == LOW) && (encTurned == HIGH)){
            encValue = encValue - encInc;
            encDir = 2;
          }
      }
    }
    encLastState = encTurned;
}
aLastState = aState;
encDir = 0;
// Print Some Status
if (encValue != lastEncValue) {
  Serial.print("Encoder Value Changed from ");
  Serial.print(lastEncValue);
  Serial.print(" to ");
  Serial.println(encValue);
}
digitalWrite(13,EncBtnValue);



}

I hope that this will be useful to somebody.