What to test low voltage auto electronics with?

[atikovi]

I can use a regular 12 volt jump box for testing window motors and the like but what about low voltage electronics that are usually at 5V? Had a rear view mirror with OnStar and wanted to test the red and green LEDs. Didn't want to risk burning them out with a 12V battery so I took the 9V battery out of a smoke alarm and used that. What would be a simpler thing to use for this? Something like this on Ebay? https://www.ebay.com/itm/30V-10A-Ad...289845&hash=item2f10fa343b:g:VZwAAOSwiBJaKeE6 or will I get electrocuted?

 

[Sine Swept]

Look into modded computer power supplies. The RC guys have lots of info out there.

 

[Metalio]

You could get just an adjustable switch mode power supply, like the one on ebay. (These are also called lab or benchtop power supplies) Here's another example that might be a bit better: https://www.circuitspecialists.com/csi3005sm.html

Like the other poster said a computer PSU is also an option, especially if you have one laying around. These will give you 12V, 7V, 5V outputs with a decent current rating. However these do not have an adjustable current limiter, which can be a useful feature from time to time.

 

[atikovi]

I don’t understand the adjustable amps. Doesn’t the item you’re testing determine how many amps it’s pulling? What’s the purpose of adjusting it?

 

[Metalio]

It essentially limits the output current, so for example if you set it to 1A you could short the terminals with a wire and it will lower the voltage so the current does not go above 1A. This can be useful if you're trying to test a device that might have a short somewhere.

 

[Dick in Wisconsin]

It essentially limits the output current, so for example if you set it to 1A you could short the terminals with a wire and it will lower the voltage so the current does not go above 1A. This can be useful if you're trying to test a device that might have a short somewhere.

So that feature would help prevent melting down a device in the event there was a short?

 

[unslow1]

Can't you use a test light with a bulb to limit the load? Maybe watch some South Main Auto or Scannerdanner Youtube videos. They also put headlight bulbs inline to prevent dead shorts.

 

[Metalio]

Yeah that's also possible, but then again even the cheapest lab power supplies tend to have a current limiter these days.

 

[theoldwizard1]

"Injecting" voltage into a device is just wrong. Start with a 12V test light. Prove to yourself that you have a good ground. Now check that you are getting power to the device through the wiring harness/fuse.

LEDs are not light bulbs. Apply any voltage source directly to them could damage them. LEDs need a CURRENT LIMITED voltage supply which is why there is always a resistor associated with them.

You need to study and UNDERSTAND some basic electronics, specifically Ohm's Law. Watch a bunch of South Main Auto and Pine Hollow Auto Diagnostic on YouTube.

 

[theoldwizard1]

Can't you use a test light with a bulb to limit the load?

Yes. A typical 12V test light, inline (in series) with a voltage source, will limit the draw to about 1/4A (250mA).

 

[unslow1]

Yes. A typical 12V test light, inline (in series) with a voltage source, will limit the draw to about 1/4A (250mA).

In one video posted yesterday Eric O. showed a test light with a vise-grip for a clamp. He mentioned switching to bulb to a 780 milli-amp. Any idea what and where on the bulb? I'd like to get one. I'd also like to make a better one with the load draw of a headlight.

 

[928'er]

If you just need a 5v source, how about a USB charger plugged into the cigarette lighter. Cut off the other end, crimp on a couple of alligator clips and you've got a 5 volt power source.

 

[bcradio]

I use a Multimeter to test them and if I need to supply power to them I would use a variable power supply.

How did you know the LEDs need a 9-volt rather than 12 volts?

 

[atikovi]

How did you know the LEDs need a 9-volt rather than 12 volts?

I didn't. Just know most electronics operate at 5v and a small 9v smoke detector battery would be safer than a car battery. And the LEDs tested fine.

 

[Metalio]

If you're in a pinch you could also create a adjustable voltage divider with a simple potentiometer. This only works well for devices with a low power draw though and you may also need an inline resistor depending on the min resistance of the pot.

Also any led that's in some kind of device that takes a 5V power supply is probably going to have a current limiting resistor.

 

[theoldwizard1]

In one video posted yesterday Eric O. showed a test light with a vise-grip for a clamp. He mentioned switching to bulb to a 780 milli-amp. Any idea what and where on the bulb? I'd like to get one.

I have ask him more than once. Silence.

I might pick up a small locking pliers from HF and do the same.

 

[tym]

Regulated bench supply would be the gold standard, along with a DMM for general troubleshooting.

 

[Tj-gord]

I use a powerprobe at work for testing and diag, but thats automotive and 12/24 volts.. might be a long shot but power probe may make a lower voltage device..would be worth google search

 

[fordnut85]

I have recently picked up one of these. Goes onto the end of your power probe, 12v in, 5v out. Haven't had a real need for it yet but for $20, why not?
https://www.tooltopia.com/power

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[unslow1]

I have recently picked up one of these. Goes onto the end of your power probe, 12v in, 5v out. Haven't had a real need for it yet but for $20, why not?
https://www.tooltopia.com/power

Sent from my Pixel using Tapatalk

Link doesn't work. Part number?
I think I figured out what you were referring to.

https://www.google.com/search?sourc...64.psy-ab..1.14.1570.0..0i131k1.0.lraM5gBq6Dk

 

[Tallpilot]

That’s awesome. Now you can get the 5V functionality of the hook without spending $350. The only question is what the current limit is.

 

[Tallpilot]

I have ask him more than once. Silence.

I might pick up a small locking pliers from HF and do the same.

He’s pretty busy. Probably by the time he is checking messages yours is buried under 100 more. It is a sweet idea though. That’s the biggest reason I like the power probe. It’s so hard to find a good ground under a rusty car sometimes or the crappy alligator clip on the test light keeps coming off.

 

[930dreamer]

This is just what I need for the ton of ford parts I'm selling. Just ordered one!

 

[fordnut85]

Link doesn't work. Part number?
I think I figured out what you were referring to.

https://www.google.com/search?sourc...64.psy-ab..1.14.1570.0..0i131k1.0.lraM5gBq6Dk

Yup that's the one

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