EcoRenovator - View Single Post - Arduino CO2 Sensor Controls PCM Fans in HRV

AC_Hacker · 02-12-13, 10:13 AM

To make the Teensy control the speed of a fan, I will use the built-in PWM feature of the Teensy/Arduino.

The PWM pin can send out a stream of pulses, hi = 5V, lo = 0V.

The duty cycle of the PWM, the percent of time the voltage is high, can be changed in 256 steps (0 to 255) from 0% to 100%, respectively.

NOTE: My Analog read pin can read in steps of 1024, so I will need to divide my analog read values by 4 before I direct them to the PWM output.

So I located the simplest Arduino program I could find and stripped out everything I didn't need.

I ended up with this endless loop PWM program:

Code:

//PWM test; PWM Value = 0 to 255

const int Brightness =  14;          //This sets up Teensy pin 14 and names it Brightness

void setup()   {                
  pinMode(Brightness, OUTPUT);       //This makes Brightness (AKA: pin 14) an output pin
}

void loop()                        //This sets up a loop
{                                  //BEGIN LOOP
  analogWrite(FanSpeed, 255);          //This sends a value of 255 to Brightness
  delay(500);                          //Delay one half second
}                                  //REPEAT LOOP

I connected an LED to Teensy pin 14, and compiled & ran code.

LED comes on full bright.

Next I changed the 255 value to 128 and re-ran. LED came on less bright.

Ditto 64 (dimmer)
Ditto 32 (dimmer)
Ditto 16 (etc.)
.
.
.
Ditto 0 (LED off)

Everything worked as I had expected!

On to the next test.

Best,

-AC

02-12-13, 10:13 AM	#34
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Exploring Pulse Width Modulation (AKA: PWM) To make the Teensy control the speed of a fan, I will use the built-in PWM feature of the Teensy/Arduino. The PWM pin can send out a stream of pulses, hi = 5V, lo = 0V. The duty cycle of the PWM, the percent of time the voltage is high, can be changed in 256 steps (0 to 255) from 0% to 100%, respectively. NOTE: My Analog read pin can read in steps of 1024, so I will need to divide my analog read values by 4 before I direct them to the PWM output. So I located the simplest Arduino program I could find and stripped out everything I didn't need. I ended up with this endless loop PWM program: Code: //PWM test; PWM Value = 0 to 255 const int Brightness = 14; //This sets up Teensy pin 14 and names it Brightness void setup() { pinMode(Brightness, OUTPUT); //This makes Brightness (AKA: pin 14) an output pin } void loop() //This sets up a loop { //BEGIN LOOP analogWrite(FanSpeed, 255); //This sends a value of 255 to Brightness delay(500); //Delay one half second } //REPEAT LOOP I connected an LED to Teensy pin 14, and compiled & ran code. LED comes on full bright. Next I changed the 255 value to 128 and re-ran. LED came on less bright. Ditto 64 (dimmer) Ditto 32 (dimmer) Ditto 16 (etc.) . . . Ditto 0 (LED off) Everything worked as I had expected! On to the next test. Best, -AC Attached Images __________________ I'm not an HVAC technician. In fact, I'm barely even a hacker...