Hypex ST180 Power Supply LED

[dtaylo3]

I have finished most of a hypex build and have tested the voltage outputs of the ST power supply to drive two ST180 amplifier modules. All + and - voltages are correct on my multimeter. Yippie! How do I run an LED off of the ST power supply LED +/-. I want to use an LED on the front panel to show the amp is on. I installed a green LED unit from radio schack, but when I hook the leads up to the ST power supply LED + and - it does not illuminate. Any ideas? What is the proper voltage out of the ST power supply LED section?

[dtaylo3]

Hmmm. Do I need a resistor before the LED?

[sofaspud]

Probably. Do you know the voltage at the LED +/- connection? If yes, divide that voltage by 0.01. That will be be resistance in ohms to use in series with the LED.
That allows ~10mA thru the LED. Too bright use a little higher resistance; too dim use a little lower resistance.

[dtaylo3]

I am getting a reading 24 volts from the LED + out on the power supply module. I am surprised it is that high. I found an online LED calculator, and looks like I will need a 1.2K ohm resistor in series with the green, pre-wired Radio Shack LED unit.
Since I ran 24 volts into the first LED i had installed on the chassis panel, I imagine it is toast? Despite the LED misfire, the rest of the Hypex amp is up and running and playing nice music.

[sofaspud]

What is the part number for that pre-wired radio Shack LED? Some (most?) of those are made to easily connect to a particular voltage, with the series resistor built in. If that's the case here, the 1.2k might work if it drops ~12V, leaving 12V for the RS LED. Kind of big "might", though.

[dtaylo3]

Here is the Radio Shack LED:

Model 276-271

Product Type >7 mm lens

Enclosure Color GREEN

The unit has a black wire on one side and red on the other. The black wire does have an area in it that looks like it may house an LED, so I was presuming that was the case and that it would work with the Hypex. Maybe it is for 12 volt vs. 24. The literature on line says nothing about voltage.

[tauro0221]

Hi,
The led is for 12 volts.

What's in the box
Green 12V LED with holder

[dtaylo3]

So at 24 volts it is getting double the voltage needed. So if I drop a 680 ohm resistor in series bofore the LED maybe that will work to drop the voltage to 12?

[sofaspud]

A 680-ohm resistor sounds about right. If that doesn't get it a 12 volt 1/2 watt zener diode in series might be the least fuss, or use a 220-ohm resistor, potentiometer, and voltmeter to dial in the voltage drop.