I made a little pcb with a 555 timer that toggles a 120v lamp on and off with a PCB relay wired to a button about 10ft away on my desk. It works ok, but when a load changes somewhere nearby, like turning off my closet fluorecent lights, or when the furnace kicks on, the relay will toggle. I also tried using a raspberry pico to control the relay in case my pcb was wrong, but it still happens very consistently.

Is there some sort of current-induction-voltage-causing fenomenon on the long button wires? if I connect a small push button near the circuit, the phenomenon stops happening....

 

First You need to outline what You are trying to accomplish overall.
Then supply a Schematic of what You have now.
Otherwise, it's just a complete guess as to what You have going on.
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Maybe use shielded cable for the LV, and earth GND the shield.
Try that first.

 

It is presumed that the circuit utilises a 555 IC and a single momentary push button switch to toggle the relay 'on' and 'off'.

The root cause of the problem could be the lengthy push button switch wiring acting as an antenna that picks up electromagnetic interference when the fluorescent light or the furnace turns on.

The problem could be solved by using a 'ratchet relay' and a push button switch and avoiding use of the 555 IC.



A single push of the button would turn on the relay and a subsequent push would turn it off.

Nandu.

 

Welcome to AAC!

It works ok, but when a load changes somewhere nearby, like turning off my closet fluorecent lights, or when the furnace kicks on, the relay will toggle.

Show us a schematic of your circuit and a picture of your board/wiring.

 

"Relay with long wire for button"

that explains everything. your long wires are acting as antenna and picking up interference. strong one can trigger the 555 because input there is relatively high impedance. low impedance circuits are much less prone to this kind of influence. this is how unshielded wires were run for 100s of miles carrying phone conversation - circuit impedance was low.

so you can try adapting values in your circuit. we cannot help much without seeing it.

if it is something like this, just reduce value of resistor at the left side (*)

 

Does seem to be inductive effect, so first step would be twisted pair to connect the switch; next step would be a shielded twisted pair, with the shield connected to ground at the circuit end.