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Topic: Logic level mosfets do not turn on, unless I touch them! (Read 2 times) previous topic - next topic

Grumpy_Mike

#10
Oct 14, 2012, 06:51 pm Last Edit: Oct 14, 2012, 06:55 pm by Grumpy_Mike Reason: 1
The other thing is that the TLC5940 just pulls down so you need a pull up to 5V or more to drive the FETs.

If only you would show a schematic of what you actually have rather than a half baked mish mash of bits of circuits then we could definitively help.

winner10920

Instead of showing the circuit you followed, make your own shematic from what you actually did, sometimes just in doig that you can realize something you overlooked

dpmattox

Sorry guys, church yesterday. I have attached an early, but applicable, schematic. I am also seeing differing of opinion on whether I should pull up or pull down the gates. As I said, the pulldowns in the schematic have not been soldered on yet. Holding the board in my hand, everything works as it should. Setting it down, nothing. Specifically, touching the Mosfet pins on the bottom of the board illuminates that channel in accordance with the running program. I am seriously considering dropping the TLC5940 in the next revision for ShiftPWM. But still need to figure out what's going on with the mosfets. If you guys are sure the IREF resistor on the TLC is not to blame, I will leave it alone for now.

Grumpy_Mike

So what part of this did you not understand?


The other thing is that the TLC5940 just pulls down so you need a pull up to 5V or more to drive the FETs.

dpmattox


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