{"id":18014,"date":"2022-08-19T12:14:36","date_gmt":"2022-08-19T05:14:36","guid":{"rendered":"https:\/\/www.makeriot2020.com\/?p=18014"},"modified":"2022-08-19T12:14:42","modified_gmt":"2022-08-19T05:14:42","slug":"pwm-controller-with-r-e","status":"publish","type":"post","link":"https:\/\/www.makeriot2020.com\/index.php\/2022\/08\/19\/pwm-controller-with-r-e\/","title":{"rendered":"PWM Controller with R\/E"},"content":{"rendered":"\n

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.<\/p>\n\n\n\n

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. <\/p>\n\n\n\n

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The PCB<\/h3>\n\n\n\n

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. <\/p>\n\n\n\n

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. <\/p>\n\n\n\n

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]<\/p>\n\n\n\n

The ICSP programming header is below that,
with a jumper to select PCF8574 interrupt on Pin D2 or not<\/p>\n\n\n\n

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]<\/p>\n\n\n\n

Another 6way Ground header, as well as the 12v input (red), follows.<\/p>\n\n\n\n

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)<\/p>\n\n\n\n

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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 ?]<\/p>\n\n\n\n

This wraps up the quick PCB description.<\/p>\n\n\n\n

Schematic<\/h3>\n\n\n\n

The Schematic is below, along with a download link ( zip format, with PNG image files)<\/p>\n\n\n\n

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Schematic_PWM-Fan-Controller-with-RE_2022-08-19<\/a>Download<\/a><\/div>\n\n\n\n

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Some more pictures<\/h3>\n\n\n\n
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\"PWM<\/figure>\n<\/figure>\n\n\n\n

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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. <\/p>\n\n\n\n

Manufacturing<\/h3>\n\n\n\n

Over the past eight years, PCBWay has continuously upgraded their MANUFACTURING plants and equipment to meet higher quality requirements, and now THEY also provide OEM service<\/a>s to build your products from ideas to mass production and access to the market.<\/p>\n\n\n\n

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