General question about duplicating voltage for test

[johns1mj]

For the last little while I have been using a model train transformer to test led lights. I can control the voltage with the dial indicator on the transformer itself.

The questions I pose are:
Can I use the transformer to duplicate signal voltage?
For instance back light on voltage?

What are the forseen problems with this?

[dick_barton]

Re: General question about duplicating voltage for test

You don't say what the voltage can be varied between or what the current is. Is it a DC controller?

[budm]

Re: General question about duplicating voltage for test

What kind of Backlight driver are we talking about? DC logic level control?
BTW, when testing the LED, always use current limiter power supply to test the LED, LED string. If you are testing the bad LED string that may have one or two shorted out LEDs, so when you apply the Voltage, lots of current will flow due to shorted out LEDs which at that point you can damage the good LEDs.
LED is a current device.

[petehall347]

Re: General question about duplicating voltage for test

one of these might get you close to what you want to do . UA723CN
obviously needs some other parts .

[johns1mj]

Re: General question about duplicating voltage for test

I am using a small dc controller lionel model 4660. It only goes up to 18 volts dc. I can control the output with its dial indicator.

So if say I wanted to test a TV that was not getting the backlight signal on, assuming its a 5 volt signal, could I fake the signal with the controler and turn the back lights on? Would I risk shorting out other components introducing additional voltage into the circuits?

[budm]

Re: General question about duplicating voltage for test

Typical control signal for ON command is around 2.5~5VDC range, using 1.5V batteries in series will be more than enough to simulate the signal, But what ever you use you should put small resistor 470 ~1000 Ohms) in series to limit the current in case you connected it to the wrong pin.
You need to control the current when testing LED so at least you should have DC Amp meter connected in series with your load so you can see how much current you are forcing into the load (LEDs).