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having some issues with a touch sensitive switch. ideas? Answered

so a little while ago i had put together a circuit for a touch sensitive switch based off the 555.
it works great, it senses when i touch it and operates an optocoupler from that.
the issue is it senses when i touch anything electrically connected to it. im currently using a power brick to power it (supplying 5v and 12v, the switch is part of a lerger project) and if i touch anything thats connected to ground the switch activates. the part that confuses me is that theres no ground plug, just the two main AC wires. Somehow its sensing through one of those wires as well, and when capitance builds up elsewhere in the system the switch activates.

as far as i know the only way for me to isolate the switch is to power it using batteries. is there any way to power it still using the power supply without it sensing things other than me touching it?



6 years ago

You have to power if from household mains. Power supply. It uses the pulse to operate . Battery wont work.

okay, but how do i keep it from sensing things other than my finger touching the sensor wire?

If You do not have to use a 555 i suggest you try this one. Made with a 4011.


i dont have a cd4011 on hand and cant purchase one at the moment, the 555 was rather simple and i had all the parts, otherwise i wouldve gone with a more reliable circuit

this one here: https://cdn.instructables.com/FUI/0KEY/GQRBNN61/FUI0KEYGQRBNN61.MEDIUM.jpg

ok, so the link didnt work.

touch sensitive 555.jpg

Try tying pin 2 HIGH with a 10 Meg resistor.

where do i put the other end of the resistor?
(i havent really ever used the terms "pulling high" or "pulling low" before..)