Switch reads 4V when on AND when off??!?!?!?

Hi everyone! I am creating a project that uses a desk lamp that has a pull chain switch with an arduino. I've tested my code using a regular push button with no problems so I know it is not the circuit design nor the board. So I tested the pull switch itself with my voltmeter and got unexpected results. When first measured, the voltage was ~4V yet when I pulled the switch it also read the same amount. I was worried that maybe I broke the switch so I checked it again with another new lamp that I had also ordered and got the same results. I don't even know how this is possible, what am I missing?

Post a schematic of your test circuit and show how you measured the voltage.

what am I missing?

Well, that’s a tough one. Don’t know. You told us what you saw. 4 volts. Okay but really that doesn’t tell us much. You said it was unexpected. What did you expect to see? We’re not there and cannot see what you’re doing. Is that AC volts? DC volts? We have no idea to what or how you’re connecting your meter, what range it is on, etc, etc.

More details required for an answer. Perhaps a schematic. Perhaps a photo or two.

Helping by way of words only is difficult. Don’t get frustrated. Just remember You’re asking for help from people that cannot see what you see and know what you know. Apply patience. Look, think, communicate. Repeat.

When first measured, the voltage was ~4V yet when I pulled the switch it also read the same amount. I was worried that maybe I broke the switch so I checked it again with another new lamp that I had also ordered and got the same results.

If you're measuring from the screw base (neutral) to ground, then yes reading 4V is possible ... even with the lamp switched ON. The neutral is shared with other loads on the circuit, in which case there will be some voltage drop on the neutral (white) wire.

If you're measuring from the tip of the lamp base to GND, then your reading should jump to full AC voltage when switched on.

Note: When measuring an open circuit, voltmeter readings can jump around as the measuring circuit is high impedance (this is normal).

Do you have a low voltage LED lamp? In this case might need to switch to DC on your voltmeter.

Be careful.

Yes I’ll agree here - details matter, in electronics almost anything can be vitally important so we need
to know exactly what you have and how you have connected it to figure out what’s really going on.

My guess is you’ve measured in circuit and perhaps in the wrong places? A switch on its own not
connected to anything won’t create a DC voltage. Everything you touch will show AC voltage picked
up from the mains wiring around you however.

Not to pile on, but.... The question is too vague; anyone attempting to answer will be forced into making a bunch of assumptions which could turn out to be wrong. That, in turn, would lead you down a blind path into even more trouble. So please, post a diagram. Doesn't have to be artistic, but it needs to communicate exactly what kind of a lamp and what you're measuring. S.

I can't help it......

I have an image in my mind of a old antique desk lamp with the switch bead chain hanging down and on the end of the chain is an Arduino board.

JohnRob: I can't help it......

I have an image in my mind of a old antique desk lamp with the switch bead chain hanging down and on the end of the chain is an Arduino board.

Might be an appropriate use for a bricked Arduino... S.

My meter reads 4 (sometimes) when I hold the probes to my tongue. :o

My meter reads 4 (sometimes) when I hold the probes to my tongue

.

This time we do not need any photos of the wiring.

JCA34F: My meter reads 4 (sometimes) when I hold the probes to my tongue. :o

My meter's probes taste bad when I set the meter on resistance and hold the probes to my tongue..

It is quite easy to imagine a situation when that will be true. If you apply your meter between ground and the end of the switch connected to the power, then that will read the same if the switch is on or off. That should not happen if you put the meter on the load side of the switch unless you have something wrong or you misidentified the switch connectors.