I am developing a system to test a power supply with outputs of +5, +12, -12, and +24 voltage outputs. If the assembly of the power supply is correct (as in the voltages are correct at certain test points I have chosen), the LEDs will light. On the other hand, if the incorrect voltage is supplied, my tester should not light the LED.

Would Zener diodes be the best bet if I hook up the LED in series with a Zener diode and a resistor? For example, if the voltage I'm testing is supposed to be +12 V, and instead it's less than that, the LED shouldn't light due to the Zener. Also, is there any way to indicate if the voltage is greater than +12 V using the same system? (besides the intensity of the LED)

Thanks in advance.

 

I would think that using a meter would be faster and resolve the exact voltage at any point a lot faster. Think about how your tester might show a positive 3 volts at a negative 12 volt terminal.

Autoranging DVM's are the way to go.

 

beenthere:

"I would think that using a meter would be faster and resolve the exact voltage at any point a lot faster. Think about how your tester might show a positive 3 volts at a negative 12 volt terminal."


dont u think zenor breakdown will occur more by don this???

 

If you check the schematic here... http://forum.allaboutcircuits.com/showpost.php?p=74640&postcount=11 you will see I've done something similar for the power LEDs. It isn't very precision, it's only function is to let me know if the 9V batteries are running down, I wouldn't use it for much else.