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Jimmy W.
03-14-2012, 02:01 AM
I am going to be undertaking a large LED Control project, I need to control 9 loads of LEDs of different colors, each color is going to be drawing about 200-450watts. Any recommendations on what to use to control this? Just a 60a transistor? Just dont know if there are any better solutions, IE triggering multiple of them simultaneously from the same output pin.

Jimmy

JonnyMac
03-14-2012, 02:56 AM
I did a 100w LED dimmer using a MOSFET; worked well, the only issue being heat management. By using a MOSFET driver (TC4427) the MOSFET is driven fully on and fully off and runs very cool.

Mark_T
03-14-2012, 03:21 AM
I did a 100w LED dimmer using a MOSFET; worked well, the only issue being heat management. By using a MOSFET driver (TC4427) the MOSFET is driven fully on and fully off and runs very cool.

I fully concur, you also need a driver to protect the microcontroller from switching transients passed back via the gate-drain capacitance I suspect - protection circuitry at this current level is mandatory really - you don't want a blown MOSFET to fry all the rest of the electronics.

EMI is also an issue I suspect.

Jimmy W.
03-15-2012, 02:45 AM
Ok, I'll look into MOSFETs, I have already thought of EMI, and planned to use as a case grounded copper project box, that will look snazzy once I powder coat it. Thanks for the tip on the MOSFET driver, I will do some research on that. Dont want to accidentally screw it up, the power supply that they provided me is pretty killer, 12v @ 9000w, 9 rails of 1000w each, with a 2.9f 60v cap on each rail output.

RS_Jim
03-15-2012, 02:24 PM
Jimmy,
You might want to consider using opto isolators to protect the prop from magic smoke release!
Jim

Lawson
03-15-2012, 06:11 PM
Sounds like 10-20 amps per LED string at 12 volts. A lot of cheap DC motor controllers for RC equipment have specs like that. The HB-25 (http://www.parallax.com/Store/Accessories/MotorServos/tabid/163/CategoryID/57/List/0/SortField/0/Level/a/ProductID/64/Default.aspx) is one example. If the LED strings run reliably connected directly to 12v, they should also work powered off the DC motor controller. If they need some current control, I'd add a "large" inductor in series with each LED string to make the LEDs look like a DC motor then limit the maximum duty cycle. Something like This (http://search.digikey.com/us/en/products/AIRD-02-270K/535-11404-ND/2660704) or the bare rotor out of a "540" size DC motor with wires soldered to the commutator. The inductor minimum inductance is largely set by the PWM frequency of the controller and more inductance reduces the ripple in the LED current.


Lawson