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Topic: Need help connecting MG-811 to UNOR3 (Read 2139 times) previous topic - next topic


Hello. I am working on my first Arduino project. I have limited knowledge of arduino, microcontrollers, and the likes, but I am learning the best I can. I would appreciate help with this roadblock, as I have not been able to find a solution.

I have received the MG-811 CO2 sensor attached to the op-amp available from sandbox(SEN-000007). I have read the product data sheet and have tried to understand it to the best of my abilities. I have a 9V power supply for the heating element. I understand the VCC will connect to 5V on the UNOR3. I know the GND will be the ground on uno.

I am assuming the VOUT could connect to any available analong in (A0,A1...A5)? Is this correct?
I have not been able to understand the connection for BOOL. It says comparator output. This is new to me and anything I have found searching has not been helpful. Later in the data sheet it says I should add a pull-up resistor to BOOL. This is great but...what size?

I appreciate all and any help. Thank you

data sheet: http://sandboxelectronics.com/store/images/SEN-000007/SEN-000007_Datasheet.pdf
sensor: http://sandboxelectronics.com/store/index.php?main_page=product_info&products_id=197


still looking for help. Ive been searching everywhere and can't find any concrete information. I found someone using the same sensor and based on the picture it appeared the BOOL was left unconnected. This doesnt seem right to me though based on my understanding of what it does.

Thanks to anyone who can help!


To start the data sheet says you need between 6-12 volts into the sensor...i used an mq sensor before and you need to 'burn it in' as it uses a heating element for readings. Just connect power ground and vout to an analog pin and read off the values in the s.monitor.

My co2 sensor was an NDIR teleaire 5004 or something like that. It uses a laser and optic filter to analyse co2 what could be more accurate if set up properley.

Look for it on all electronics.com


May 26, 2013, 06:26 am Last Edit: May 26, 2013, 07:38 am by newbie1234 Reason: 1
Have you figured this out?  I am in the same boat as you.  I also purchased the MG811 carbon dioxide sensor module for Arduino from Sandbox Electronics.  I hooked up my 6V power supply to the barrel connector on the Sandbox board.  I connected the black wire (GND) from the Sandbox board to Gnd on my Arduino Uno.  I connected the red wire (VCC) from the Sandbox board to 5V on my Arduino Uno.  I connected the yellow wire (VOUT) from the Sandbox board to A0 (analog pin 0) on my Arduino Uno.  I connected the green wire (BOOL) from the Sandbox board to digital pin 0 on my Arduino Uno.  Then I copied the Arduino code that was included in the Sandbox datasheet
The code compiled, but when I ran it, the following kept scrolling on the Serial Monitor:

=====BOOL is LOW=====
SEN-00007:  0.00V     CO2:  -18346ppm

This isn't right, but what have I done wrong?  I didn't understand the part about the pull-up resistors that was mentioned in the datasheet.  Is that the problem?  If so, what do I need to do?  Any suggestions are welcome!  Also, I noticed that the MG811 got really hot when I was running the Arduino code.  Is that what is supposed to happen, or have I broken the sensor?



Did any one of you figure out how  to connect the bool pin to the arduino?
Any help would be appreciated.


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