DiyLightAnimation
Hardware => Bobcat DMX Servo Controller => Topic started by: lightsup on March 14, 2012,
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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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Hi Alan,
Yay! My first chance to contribute on this forum.
Consider some of the driver circuits at these links:
http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/ (http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/)
http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/ (http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/)
Or consider a simpler, more compact solution in the ULN2803 Transistor Array:
http://www.onsemi.com/pub_link/Collateral/ULN2803-D.PDF (http://www.onsemi.com/pub_link/Collateral/ULN2803-D.PDF)
Each transistor channel can handle 500ma and you can gang them together for higher current needs.
Best,
Michael
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Thanks Michael this will help in my project, alots of options.
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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)
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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.
(http://www3.nbnet.nb.ca/alaindes/mosfet350led.JPG)
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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
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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
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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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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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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.