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Quick question . I have a 400ma power supply does that mean I could only wire 20 LEDS that are rated at 20ma?

4 Replies

PKM (author)2008-05-04

What "400ma power supply" usually means is if you try and draw more than 400ma for a long time, the supply may overheat and fail. If you try and draw significantly more than 400ma, it will probably fail quickly. If you wanted to draw 450ma for ten seconds it would probably be ok. If it's supplying 400ma at 12V, however, that's equivalent to 1600ma at 3V (common LED voltage drop) if the voltage were to be stepped down. If it was supplying 400ma at 3V, then your assumption is correct- the results largely depend on the output voltage of the supply, how you intend to wire up the LEDs and their desired voltage.

westfw (author)2008-05-04

Yes, depending on voltage. A 12V, 20mA power supply can put 20mA through at least 3 LEDs in series, so a 12V 400mA supply could do 20 strings of 3 LEDs.

Mr. TiKi (author)2008-05-04

Ok thanx I understand now

GorillazMiko (author)2008-05-04

No. Just kidding, I don't know.