Can I still find the voltage given without negative wire

Other Hardware Sensors
1

So in my car i am given a wire tapped into the positive wire from a turn signal bulb, however i do not have any access for the negative of that turn signal bulb. I was wondering if i could see the voltage change from the turn signal using a voltage sensor for the arduino uno that is rated for 0-24v. the method i was thinking was just to connect the positive wire from the bulb into the positive for the sensor, and a random wire connected to a ground, to the negative wire on the sensor. Would this work? I tried this with a current sensor I did not receive any change in current from it

2

Isn't that how you would measure the voltage with your multi-meter: red lead to bulb +ve and black lead to any convenient ground, since the -ve side of the bulb is the vehicle ground. Verify that works first....

3

Yes, you'd measure between the car ground, and the positive side of the bulb.

As always when working with your car, be careful to not accidentally break a wire to your turn signal, which is a vital piece of safety equipment. Make certain it still works afterwards.

Also, is your project, by any chance, adding additional lighting effects to make the turn signals look cooler? Be aware that laws regulate what colors (and IIRC, at least in the US, some other parameters) of lights you are allowed to have on the outside of a car (so that other drivers are not confused by ambiguous lighting, and don't mistake your vehicle for an official vehicle, etc), so make sure to check the laws in your jurisdiction.

4

gotmilk674:
. . . i was thinking was just to connect the positive wire from the bulb into the positive for the sensor, and a random wire connected to a ground, to the negative wire on the sensor. Would this work? I tried this with a current sensor I did not receive any change in current from it

This connection is correct for measuring voltage but not for measuring current.

If you tried this with a multimeter set to measure current then you most likely have blown the fuse in the meter. In most cases the voltmeter will still function but the ammeter and ohmmeter won't function until the fuse is replaced.

Don