The sensors has arrived

Yesterday the sensors I had ordered arrived, I had ordered the Figaro TGS822 and the MQ-3 from Hanwei Electronics. Since this type of sensors require a burn-in of 24-48 hours I wired them and applied some power. I had a suspicion that the sensors were actually going to be identical in function but perhaps I was wrong since they do actually use different amounts of current. The TGS822 sensor draws 117 mA while the MQ-3 draws 102 mA. It might just be that different individuals use different amount of current, further experimenting will tell if they also measure differently.

One thing that I didn’t expect was that the pins of the sensors are placed along the side of the round sensor following the curvature. This makes it impossible to stick them into a breadboard, since the pins will not line up with the holes in the breadboard, so I had to solder some wires to the connectors.



10 svar till ”The sensors has arrived”

  1. I 3-D printed a case and mouthpiece for the keto sense and had a buddy wire up and program It. it turns on warms up and loads okay, but when I go to use it, it seems unresponsive any ideas on troubleshooting.
    Thanks for the diy great website
    Montana, USA
    Jesse crumb


    1. Hi Jesse

      The first thing to check is if the Arduino can detect any values from the gas sensor. As I understand it you are not super familiar with Arduino so I will try to help you pinpoint the problem.

      When you first power on the Ketosense, the LCD should display somthing like ”Warm up” it then starts counting for 20 seconds on the top row on the LCD. While it is counting there are two values displayed on the second row, those values are the raw sensor values and should be decreasing while it is warming up. If both values are equal and static then there is a problem with reading the gas sensor. If they are either 0 or 1023 then it is probably wired wrong. Can you please tell me what the values are during the warm up?


      1. It does count down and the values stay high but the values do drop. Untill they get low and then it will say please blow to start but the values will not change when you blow the humidity and temp will not change everything stays the same


      2. The humidity and temp should not change that is ok. What is the value shown when it is starting? What does it drop down to right before it stops counting? Just to make sure that it’s not just to low concentrations of acetone can you try to just open a bottle of nail polish remover or acetone close to the sensor. No need to give it a puff of acetone just have it open and wave it around close to the sensor.


      3. When it starts it said
        time to warm up
        Check dht sensor
        H 35. T 30. 1counting up
        Max172. Min 171 (and droping)


      4. Ok i opened some acetone close to it and blew in the general direction and the max and now went up to 5 real quick then the now dropped down to 0 … So does this mean that when i think im in ketosis and the keto stix say i am in ketosis i really not ?


      5. Ok i think i have just been using it wrong when i plug it in. It counts down and says please blow to activate then if i push a button on the left it brings up a screen that said
        H:60 T:28 R:104
        Now: 0.00 Max:0.00
        What does the R stand for? And if i get the acetone close the numbers go up and the max will stay


      6. It might be that the sensor you have is not behaving exactly as the one I used. The R value is the raw sensor value, that value is then used to calculate the mmol/l value that you normally see. I have written a user manual that you can look at here:

        Here is a translation chart where you can see what each R value corresponds to in mmol/l

        You should also only measure breath ketones after fasting to in the morning before eating anything is optimal.


      7. Ok that helps i also noticed that if i start the unit and let it sit the readings will go to now -0.02 max -0.02 also i test my self in the am i use a ketostick and it may read .5 – 3.5 depending what i had for dinner i will try replacing the sensor and see what that does the R value chart starts at 200 but the value i get on the unit is only in the 100’s


      8. What sensor did you end up using the mq-3 or the tgs822 ? I ordered 2 of both


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