Hi, I,m setting up a soundsystem in my room, and I wondering if there was a way to set up some LED arrays to go with it.
here's the catch: I am limited to materials that can be gotten at any radio repair place, as online purchases don't ship here. this means no ICs.
is there any way of doing this?
my electronics skills are rather basic, but I want to fix that.
thanks,
Japa
On Nov 3, 6:24 am, Japa wrote:
Hi, Japa. You can make a simple LED driver with just a diode, a cap, a few resistors and a darlington power transistor, if you've got a spare DC wall wart that can power your LED array. This also assumes you have current limiting resistors on the LEDs.
Here's how it would work (view in fixed font or M$ Notepad): | | .---o---o---o---o---o---o---o---o-------------. | | | | | | | | | | | | | | | | | | | | | | | V~ V~ V~ V~ V~ V~ V~ V~ V~ | | -~ -~ -~ -~ -~ -~ -~ -~ -~ | | | | | | | | | | | | | .-. .-. .-. .-. .-. .-. .-. .-. .-. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | '-' '-' '-' '-' '-' '-' '-' '-' '-' | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | '---o---o---o---o---o---o---o---o | | | | | |C | | .---o | | | | | | 1N4002 ___ ___ B |/ | 12VDC --- | o---->|---|___|--o----o-|___|--o-| | Wall - | 1K | | 1K |> | Wart | | +| .-. | |/ | | To 10uF --- | |100K '-| | | Speakers 25V --- | | |> | | | '-' o | | | | |E | | o----------------o----o----------------o-------------' | | (created by AACircuit v1.28.6 beta 04/19/05
Use an NPN power darlington transistor like a TIP120 -- this will easily switch half an amp or so, which should be more than enough for a lot of LEDs. If you double (or triple or quadruple) up LEDs with each current limiting resistor, you could literally drive a hundred
20mA LEDs with this setup.Here's how it works: The diode keeps speaker voltage from reversing and destroying the Darlington and cap. The 10uF cap charges up through the first 1K resistor. When speaker voltage gets over 2V, base current starts flowing through the second 1K resistor, the darlington starts to conduct, and turns on the LEDs. The 100K resistor acts a a bleeder to bring down the base voltage fairly quickly (1/2 to a couple of seconds, depending on the speaker voltage). If you feel the LEDs stay on too long or not long enough, play with the value of the 100K resistor to change the decay time.
Be sure to put a good heatsink (5 watts or more) on the NPN darlington
-- at certain volume levels, it's gonna get hot and smoke unless it has a way to dissipate the extra heat.
Inexpensive, easy, and all components are available at any radio repair shop.
Good luck Chris
Have you tried Google?
What/when did you want the leds to do? and what signal will you have to drive them?
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Yes - many:
Hope This Helps! Rich
Thanks.
this circuit looks simple enough for me to tackle, and should keep me until I can muster the courage fore some of those more elaborate ones.
thanks a lot.
I would have done this search myself, but I hadn't the faintest clue what they were called.
No problem! :-) This is .basics, where there is no such thing as a dumb question. :-)
Welcome to the loony bin! ;-)
Cheers! Rich
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