[dorkbotpdx-blabber] ARRGGHH - Please check this circuit

[Eric Garner]

my first question is "what's supplying the power to all this?" is your
supply hefty enough to supply (10W* 36 LED's+ Losses=380-400W?)



On Mon, Jan 12, 2009 at 5:53 PM, Hans Lindauer <armatronix at sbcglobal.net> wrote:
> By now, many of you have been blinded by my MIDI LED project at the
> meetings.  Hopefully some of the electronics experts out there can help me
> get this thing working so I can get on with my life.
>
> The trouble is, I've been trying to run the whole thing off of 5V, but when
> the lights come on fully, it appears (I don't have a scope to confirm this)
> that the voltage drops below the minimum for the microcontroller, causing
> the microcontroller to reset.
>
> I had hoped that putting a capacitor on the microcontroller's power rail
> would help (I even figured out to put a diode going into the cap), but it
> still isn't working.  I think the problem is that 5V doesn't provide enough
> overhead, and trying to use caps to take up the slack is only going to be
> marginal at best if I want to be able to run the LEDs at full brightness
> (which I do).
>
> So my next step is to try powering it off of 12V instead of 5V.  BUT... when
> I tried that before, it burned out my LED after a few minutes (and I can't
> afford to burn out too many of those, they're expensive).  The guy who
> posted the driver circuit I'm using claims that it works for 3V-60V, but
> obviously I've found an exception to that.
>
> I don't understand this stuff enough to know what's the problem here, but if
> any of you do, could you please let me know what to try next?  And if
> there's a Better Way (that won't break the bank or introduce a lot of
> complexity), I'm open to suggestions.
>
>
> Here's the driver circuit; I have 36 of these in the system, hooked up to
> the Dorkboards' PWM outputs:
>
> I=1A thru the LED (metered at 5V input)
> R1=100Kohm, 1/4W
> R3=0.56ohm, 3W
> Q1=Fairchild 2N5088BU Small Signal NPN Transistor  data sheet
> Q2=Fairchild FQP50N06L 60V N-Channel QFET Logic Level MOSFET  data sheet
> LED=LedEngin LZ4-20MA10 Hi-Power LEDs on MCPCB RGBA 10 Watt Full Color  data
> sheet
> (I'm not using the amber die on the LED)
> Link to Instuctables page for this circuit
>
>
>
> Thanks!
> -Hans
>
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-- 
--Eric
_________________________________________
Eric Garner