Measuring Light Bar Current Draw

[Some Random Guy]

I don't think LEDs have static resistance, the resistance changes based on the input. Sucks, cause that'd be the easy way P=V/R.

Using voltage drop like your first example is a great option.

Little archaic, but another option, from the amazon pic, looks like it's running a green (30 amp) fuse. Swap in a couple smaller 50 cent fuses, and it'll blow when you get below the current (of course turn the switch off when swapping).

Yeah, I don't know my LED's enough. My understanding though is that if the LED is producing light, it's resistance is basically 0. There's only a super small voltage window where it is allowing current to pass, but actually presenting resistance. This is why in basic circuit stuff you just account for a Voltage Drop (which has no bearing if trying to measure peak current). Regardless if 5A are flowing or 25, the Vd stays effectively the same.

Sponsored

 

[Some Random Guy]

You don't need a new multimeter. Just measure the voltage drop across the fuse: https://www.meeknet.co.uk/E64/Fuse Voltage Readings To Give Current Readings.pdf

See, I knew someone smart would show up!

 

[CaJLMetalHead]

You could use a Shunt Resistor in series with the lightbar to measure current... something like this.. but .. in reality.. I would rather spend that money on a clamp meter instead..

Fielect 300A 75mV DC Current Meter Shunt Resistor Resistance for DC Ammeter Shunt FL-2 (amazon.com)

Sponsored