That makes sense. Thank you for your input! I’ll be working on this later this week and will try powering direct from the pi.The problem with your original wiring becomes clear if you consider the current flow through the sensor transistor. Pi 3v3 supply, pull up resistance, gpio pin, yellow wire, transistor, external supply ground then somehow it needs to find its way back to pi ground via 2 supplies and your mains wiring. A tortuous route with opportunity for mains hum.
Linking grounds may work but the two ends are at different potentials and could well induce a high alternating current which is best kept away from your pi. You avoid this if you power the sensor from the pi. A general rule is to keep grounds shorthand clean. You could power the lot from the pi of course and simplify your setup.
Phil
Statistics: Posted by gbluff02 — Mon Jan 01, 2024 1:10 am
