DIY Pro Kit: Why are temp & humidity both zero?

Just assembled the DIY Pro kit. TVOC, CO2, PM all seem to be working. They give reasonable numbers on the OLED display.

However, the C and H readings are both zero. What’s wrong?

I removed the pullup resistors on the SHT3X as the instructions suggested. I don’t think I botched the removal – gentle heat, lots of flux, tiny iron tip – nothing burned. See photo:

Do I need to put jumpers in place of the resistors I removed?

For your second question. No removing the pullup resistors disconnect the 3.3v to SDA and SCL. Connecting them directly means those rails will always at 3.3v and so no signals can be sent.

For further troubleshooting. Try removing other sensors(mainly SGP which is on i2c bus) and see if the SHT does work. It could be that there is no pullup anymore so putting a simple 10k resistor between 3.3v and SDA and 3.3v and SCL anywhere on the board can help in testing your sensor is working.

Thanks very much for the suggestion to remove sensors. It seems my SHT3x isn’t dead.

What’s working now: I removed the SGP30 from the 3v I2C header and plugged the SHT3x in its place. Now I can see reasonable values for temp and humidity on the OLED display. Strangely, the TVOC has a value of 100 on the display, even without a sensor plugged in.

However, I still can’t get data from both the SHT3x (temp and humidity) and SGP30 (VOCs) at the same time.

Any ideas of what’s going on and how I can get both sensors to work simultaneously?

Adding resistors worked. Both sensors work simultaneously now.

I added 10K resistors between 5V and SDA and between 5V and SLC. (Putting them on the 3V line didn’t work.)

I probably should have left the resistors on the SHT3x module since there are no resistors on the SGP which comes with the AirGradient kit. The instructions weren’t really clear on this point, and I wasn’t smart enough to figure it out without the forum’s help. Thank you.

If you use the AirGradient SGP41 module there is no need to remove any pull ups anymore. I will check the documentation to see if I need to make it clearer.

Nice to hear you have it working. Remember that most SGP30 modules aren’t made for 5v so that can result in damage over time.

And only pullup to 3.3v OR 5v. I prefer 3.3v to be on the safe side. If 10k doesnt work you can lower it a bit for a stronger pullup.