Description

PCB_PWM-Fan-Controller-with-RE

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_2022-08-19Download

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.

Code

Code for Rotary Encoder

Arduino

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);
  encTurned = LOW;
  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;
        }
    }
 }
 lastEncBtnState = encBtnState;
 // Handle the Rotary Encoder Dial
 aState = digitalRead(encFWD);
 if (aState != aLastState) {
    if (digitalRead(encREV) != aState) {
       if (encTurned == LOW) {
          encLastState = encTurned;
          encTurned = HIGH;
       } else {
          encTurned = LOW;
       }
       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);



}

Schematic and Layout

Schematics

Schematic_PWM-Fan-Controller-with-RE_2022-08-19.zip

Download BOM(Bill of materials)

Aug 22,2022

669 views

PCB_PWM-Fan-Controller-with-RE

2 Layers PCB 51 x 98 mm FR-4, 1.6 mm, 1, HASL with lead, Black Solder Mask, White silkscreen

12v PWM Blower/Fan Controller with Rotary Encoder support, with ATMEGA 328P. Optically Isolated Relays and additional GPIO breakouts

669

Published: Aug 22,2022

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