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Main => Main Forum => Topic started by: Stormrider on March 24, 2008, 06:55:17 am

Title: On status led
Post by: Stormrider on March 24, 2008, 06:55:17 am

For a wooden control panel with a psx pad hack, how could I add a led that turns red when the panel is plugged into the adapter and the computer is on?

Title: Re: On status led
Post by: DaOld Man on March 24, 2008, 08:49:52 am

If the psx hack has +5vdc and ground, just wire the led between those two points. You will need to put a 330 ohm resistor in one lead of the led.
I dont really know about the psx pad, so i cant elaborate more than that.

Title: Re: On status led
Post by: Franco B on March 24, 2008, 10:07:29 am

Won't the resistor value depend on the LED? The LEDs im using at the moment require a 100ohm resistor in series.

You may want to use a panel mount LED similar to these for a nice clean install.

(http://img.photobucket.com/albums/v325/Francoberasi/Indicators-1.jpg)

Title: Re: On status led
Post by: DaOld Man on March 24, 2008, 10:38:29 am

Yes it would depend on how much current the led draws. I use 330 as a general resistor.
It works with most leds that draw approx 20 ma at 5 volt.

To choose the resistor for the led:

Vs-Vd/LedIc =Rx

Whereas:
Vs=supply voltage (5 in this case)
Vd= led voltage drop
LEDIc= current draw of the Led
Rx= resistor in ohms.

If the pulls 10 ma and drops 2.1 volts then:

5-2.1=2.9
2.9/.010=290 ohms

So yeah, you are right 330 would be a little high.
If the led draws 20 ma (probably most likely), then a 145 ohm resistor will be needed.
You just need to check the specs on your led before choosing the resistor.