After I typed my response, I actually read yours. Its about 5pm here and you may not hear from me until tomorrow morning.
I suspect the SHT and SGP boards both have I2C pull-ups, I wonder if that’s causing a problem? I2C Pull Up Resistors — Rheingold Heavy
Yes, this is also something we are currently looking in. It seems that the TVOC modules have different pull-up resistors.
We have the kit running successfully with the CJMCU-30 SGP30 module which uses a 8.2k pull-up but it seems the other modules use a 10k pull-up that creates issues in conjunction with the SHT / display and crashes the i2c bus.
Will keep you updated on what we find out.
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The new SGP unit I acquired locally also did not work, so hopefully other avenues are more successful.
It looks like we have been successful in getting the TVOC running by removing the pull up resistors on the SHT temperature / humidity sensor.
We are doing a few more tests and then I will post some images and instructions if it’s confirmed to work.
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We successfully verified that removing pull-up resistors fixes the issue. You can remove any pull-up resistors of any i2c device so either the OLED display, the SHT, or SGP module.
The easiest way would be to remove it on the SHT3x (Temperature/Humidity) module.
The pull-up resistors are the two marked in red:
The best way would be to remove them with a soldering iron. You could also clip them off but then there is the risk that you damage some of the underlying PCB traces.
It would be great if you could share your results after removing it and post any questions etc. you might have.
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Could you explain why this fixes the issue?
My guess: having multiple pull-ups puts too much current on the I2C bus, and the devices can’t sink that much current when trying to pull it low.
@awh @johnsom @sabertooth @Fenaer @ExplodingLemur did you have success removing the pull-ups or are you still facing issues? It would be great to get your feedback so if it works I will add it to the built instructions.
I removed the pull up resistors from the SHT temp sensor. It seems to be working OK for now.
Resistors were easily removed with some heat from my TS-100 and an exacto knife. Have not had a chance to install it yet but will a little later today.
Does anyone know the accuracy of the PMS5003 PM sensor?
The sensor from the PCBv2 kit is reading 5-6 ug/m3 while the the one from this kit is reading 0-1 ug/m3.
Both are in the same room nearby each other.
I was able to install the modified SHT-30 (resistors removed) and validate that this fix works. Thank you for the fix.
Sorry to reply to such an old post. Just discovered this and looks like I missed out on the first run. Is there a new waitlist for the next batch? The Google Forms link here says the waitlist is closed. Thanks!
We typically see them closer together but it is still within specs: ± 10ug/m3 if under 100ug.
We will restart selling them very soon. The new waiting list is here: https://forms.gle/AHdQ1Arx1ZZ27Djv6
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What I did was I took a fan and pointed it at the sensors, they have now equalized with each other.
I think the 3D printed case for the PCBv2 I have allows more airflow for the sensor.
Will there be an upgrade kit (pcb/case only)? I don’t see that on the form.
Hi
Is source code available for how the “Larger OLED Display” is coded?
Keep up the good work…
The U8g2lib library is used for communication with the OLED display. Source code is available here if you’re curious.