Unstable reading when using external power supply

Hello, im trying to get a votlage reading (with analog read) from a sensor on an analog pins of a Photon and i observed some weird behavior. When i supply the input 5v voltage from a Meanwell APV 8-5 i get noisy reading, meaning the bit reading is all over the place. On the other hand when i supply the input 5v from a regular table power supply the readings are stable both in bits. So my question is what can i do to fix it? Maybe a suggestion for a different small sized power supply that doesn’t have this problem. I need this system to be modular so just working with the bench one is not really a solution.

PS: im guessing that the problem is caused by the differences in ground between the supplies, but have no idea how to overcome it.

@coconut ,

I like the Meanwell power supplies in general but, in this case, it could be that you are not using the right tool for the job. This power supply is designed as an LED driver which can put strong current demands on the supply. If you look at the specs from the data sheet below, there can be significant ripple in the supply which is OK for LEDs but may be impacting your measurements:

I have had good luck using this power supply and, it seems to have much lower specs for noise and ripple:

One other point, you may want to try measuring these voltages with both the WiFi module connected / on and disconnected / off. I use the Boron and, in this case, I try to collect my measurements and then power up the cellular modem and connect to Particle to report.

Hope this helps,

Chip

1 Like

Thank you very much chipmc,
I will try it.