Author Topic: How to controll RGB 350 MA LED  (Read 2749 times)

Offline lightsup

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How to controll RGB 350 MA LED
« on: March 14, 2012, »
Hi I want to controll 350 Ma RGB led with my DMX servo controller. How would you go about it since the controller can only handle 120 Ma. can a board be made with Jfett or Mosfett or transistors to take the extra load.
Alan.
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Offline mmorlan62

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Re: How to controll RGB 350 MA LED
« Reply #1 on: March 15, 2012, »
Hi Alan,

Yay!  My first chance to contribute on this forum.

Consider some of the driver circuits at these links:
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Or consider a simpler, more compact solution in the ULN2803 Transistor Array:
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Each transistor channel can handle 500ma and you can gang them together for higher current needs.

Best,

Michael

Offline lightsup

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Re: How to controll RGB 350 MA LED
« Reply #2 on: March 15, 2012, »
Thanks Michael this will help in my project, alots of options.
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Offline n1ist

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Re: How to controll RGB 350 MA LED
« Reply #3 on: March 15, 2012, »
For a 350mA LED, I would use a constant current source and let the LED outputs on the servo board drive it.  If the LED driver has a PWM pin, that would be best, but you should be able to use an N-channel FET (gate to the servo board, drain to ground, source to LED's cathode, constant-current source or resistor between power and the LED's anode, and a pullup on the gate)

Offline lightsup

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Re: How to controll RGB 350 MA LED
« Reply #4 on: March 22, 2012, »
Well I tried this circuit and the LED come on and stay on with a vixen sequence running. when I disconnect it from the dmx servo board it goes off and when I touch the 500 kohm resistor to 6 volt power source it turns on and when I disconnect it goes off. then reconnect to the gate to the dmx board led output positive side it come on and stay on with a vixen sequence running. Connected a regular led 20Ma directly to the dmx board and it works like it should.
Here my circuit I am using can some body give me a little help Pleaase and Thank you.

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Offline rm357

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How to controll RGB 350 MA LED
« Reply #5 on: March 22, 2012, »
A single transistor circuit is going to invert the pulse width modulation.

0 = full on, 255 = off

You need a two transistor circuit to invert the signal twice... The good thing is that we are using the transistor in on/off modes only, so there is no need for a complex biasing circuit.

If I successfully attached the picture, something like this should work. For the MOSFET, I'd use the same one we use on the mr16 if it meets your power requirements.

RM

Robert
Warner Robins, Georgia, USA

Offline rm357

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How to controll RGB 350 MA LED
« Reply #6 on: March 22, 2012, »
If you use the circuit in my previous post, be sure to include a resistor to limit the current, and the 5 or 6 volts you are using to power the board should work fine - the 12v is just what they were using to control a motor.

RM
Robert
Warner Robins, Georgia, USA

Offline lightsup

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Re: How to controll RGB 350 MA LED
« Reply #7 on: March 22, 2012, »
thanks RM for the help. I just tried it and this time it remain off when connected with vixen running a sequence same as before but opposite result no blinky blinky.
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Offline lightsup

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Re: How to controll RGB 350 MA LED
« Reply #8 on: March 22, 2012, »
I just check with a voltmeter and its a negative output on the bobcat dmx board so I need a PNP transistor in this case refresh my memory please its been a long time I did this type of electronics.
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Offline lightsup

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Re: How to controll RGB 350 MA LED
« Reply #9 on: March 22, 2012, »
got it with a pnp like you said its reverse on is off in vixen . hey thanks for the help. like I said its been a while I used transistor, I guess its like riding a bike it come back after a few falls.
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