HTCC-AB02S RGB flashing when temperature is below zero

In my GPS tracker program for the AB02S I wanted to use the RGB led for my own purposes, so I set
LoraWan_RGB=0 and manually configured the led to glow red for error conditions.

All this worked perfectly, but when I took it outside on a cold day to test the tracking, the RGB led started flashing unexpectedly.

It seems to flash when Lora radio communication is happening.

This isn’t a problem for me as the finished device won’t get cold, but I thought you might want to know about this.

To reproduce this I put it in my freezer (in a plastic bag)


1 Like

Seem the LED and Lora draw too much current and the Li-ion battery cannot provide such a current at low temperature.

Did you power the unit by battery? If yes, please check battery voltage or 3.3V at low temperature.
Powering the unit using an external DC power supply.
Reduce the brightness of the WS2812 LED from 100% to 10~25%


Yes, it was running on battery power, I added a display of the voltage to the OLED and the voltage is low (3V) when this happens.

Thanks for the info.


please rerfer this link:New release of AB02S-V2

I also have a number of AB-02S boards and they exhibit the exact same behaviour. There seems to be a problem when manually setting the brightness to 0,0,0 for the red, green and blue channels. If I do that, the LED works normally when warm but goes crazy when it’s cold. If I set 0,0,0 then call pixels.clear() then it actually shuts off the LED properly. The LED still might get weird when it’s on, but at least it turns off properly. I hope this helps!

Cheers, I’ll try that, as the RGB is only used, rarely, to indicate error conditions this should hopefully improve battery life.

I’ve since tested by putting two of these in the freezer. pixels.clear() completely fixes the problem. The LEDs operate normally even when very cold.

I’m not sure why just setting the brightness to 0,0,0 causes an issue. Oh well.