General • Noise and transients when using VSYS

Hi All,
I turn to you after a week of trying anything I could find to resolve this.

I am using a Pico WH.
The problem started when I noticed that relays I am controlling using GPIO seem to flutter erattically when they are "off".

The project is still in the prototyping phase and is on breadboards. The first thing I turned to was EMI. When that was off the table (tested without wifi) I turned to power supply stability.
I have tried endless options, but when the same problem resulted when using a high power lead acid battery.... I decided that was not the power supply noise.

I am using a 7805 to supply power to VSYS.
I have used filters of all sizes to no avail.

The noise and transients appear on both my 5V supply as well as the aforementioned GPIO.

The important thing is actually that all this goes away when I power the circuit and pico using the USB connector.

So what I get now with a 7805 supply, coming from a stable, high output lead acid battery is as follows -
1. 5V to VSYS - noiisy
2. 5V to VBUS - noisy
3. 5V to USB connector - no noise.

What am I missing ?

Statistics: Posted by djinng — Thu Feb 29, 2024 1:55 pm — Replies 0 — Views 20

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