[sdiy] LED driver cable length

[Matthew Smith]

Quoth Dave Kendall at 12/09/11 21:36...
> Hopefully an easy one. The band I'm in uses visual clicks for count-ins 
> in some numbers, so there's a plan to give the drummer and the 
> guitarists a couple of boxes, each with an LED indicator responding to 
> a Midi to clock converter driven from the sequencer in a synth. The 
> plan is to have the unit in a 1U rack, with a couple of ordinary 1/4" 
> TS jack outputs to run to the LED boxes - anode = tip, GND = sleeve. 
> The cable runs would be up to 30 feet.
> 
> Can anyone see any potential problems using this scheme? The drive 
> voltage for the LEDs is 5V via a transistor on the board.

I'd say just allow for dirty contacts and resistance of the cable when 
calculating the series resistance for the LEDs.

If the series resistance comes to 220R without the cables, maybe drop it 
to 200R? You can put a bit more current through LEDs when pulsed anyway.

Possibly the biggest issue could come from stage lighting striking the 
LED box so you can't see the damn thing anyway.

-- 
Matthew Smith

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