How can I use cm1106 co2-Sensor?

Using Arduino Sensors
#1

I bought a cm1106 co2 sensor (user manual attached)
and tried to read out the pwm signal

byte PWM_PIN = 3;
 
int pwm_value;
 
void setup() {
  pinMode(PWM_PIN, INPUT);
  Serial.begin(9600);
}
 
void loop() {
  pwm_value = pulseIn(PWM_PIN, HIGH);
  Serial.println(pwm_value);
}

it returns always zero. What is wrong?
thanks for your help!

CM1106 (1).pdf (428 KB)

#2

If the sensor behaves as datasheet shows: connector 4, pins 1,2,4 are used
Make "pwm_value" unsigned long (it is microseconds..)
Add a timout parameter of eg. 2 secs.

#3

thanks for helping!
Yes, that's how I connected it. The changes didn't help, it still returns zero:(

Is it easy to get the values via Serial (UART)?

#4

If the sensor is working according to datasheet, PWM should work.
pwm_output.jpg

To test this (without a scope) connect the output to mic in on a PC - listen for ‘clicks’ every second
Make sure the sensor gets enough power. Arduinos 5V-supply should be OK

#5

thank’s!
On an oszilloscope there seems to be an 0.3 V pwm signal of the right length.
So do I need to amplify this?

#6

Maybe.. I'd try with a pullup_resistor.. range 3k3 .. 10k. in case of an open collector output.

#7

.. yes, thank you very much, now I get a signal, and it reacts to co2.
But it is only stable, if the oszilloscope is connected too. Does this make sense?

#8

NO…strange!
Verify good connections. Stronger pullup? (1k…2k ?)

as you got the scope - can you read (see) the serial output?
I saw the datasheets from the Chinees site. They tell no details.

#9

thanks, probably some connection was wrong - now I get a good pwm signal,
although the calibration seems not to fit with the datasheet.

I attached the UART Comunication protocol. (I havo no oscilloscope at my place, so I could not look for this signal on it)
I have never used this UART Comunication - are there example programs which can be easily adopted to this protocol?

UART-Protocol_cm1106 .pdf (230 KB)

#10