Relay wiring question

[xr4ti]

I'd like to set up a 'master switch' for my radio equipment, and I'm thinking of using a 4 pin automotive relay to do so.

Would it be wise to switch the negative side, or the positive side? I've heard of it being done in both ways. What I'm switching is the lead running from the battery to the barrier strip that distributes power to the radio, GPS, and 5v power supply.

The relay pinouts are:

86 Ground
30 Input
87 Output when relay is active
85 Positive input to trigger relay coil.

[N_Jay]

Switch the hot.

[TBennettcc]

Mind if I ask why you're using a relay? Is the barrier strip going to be at a different voltage?

Typically, a relay is used to electrically isolate two circuits while using one to switch the other.

Any reason you couldn't just use a plain old rocker switch?

And I agree with N_Jay, switch the hot.

[N_Jay]

you use the relay to not run the heavy to the switch location.

[Citywide173]

Originally Posted by TBennettcc

Mind if I ask why you're using a relay? Is the barrier strip going to be at a different voltage?

Typically, a relay is used to electrically isolate two circuits while using one to switch the other.

Any reason you couldn't just use a plain old rocker switch?

And I agree with N_Jay, switch the hot.

When using a relay in a master switch configuration, you're allowing the relay to handle the load (which it's made to do) and allowing the switch to be of a nominal draw. If you used a 20 amp switch, it could possibly be done depending on the specific radios being used, but the relay with a 5 amp switch is a safer option, as you don't have to worry about excessive load on the switch and the fire hazard associated with it.

I also agree, switch the hot side.

[xr4ti]

Yep, my purpose of the relay is to have a smaller, discrete on/off switch that can shut off the whole works. Thanks for the input and comments, I will switch the hot side.

[jparks29]

make sure to use a diode to block voltage spikes...