MOSFET LED Drive (eXperimental)

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opossum
 
Posts: 636
Joined: Fri Oct 26, 2007 12:42 am

MOSFET LED Drive (eXperimental)

Post by opossum »

Here is an eXperimental DIY TV-B-Gone that uses a power MOSFET to drive the LEDs. The goal of this desigin is to allow rapid firmware developement. The AVR can be easily reprogrammed in circuit (no heavy load on any I/O lines) and the LEDs are protected from long duration pulses that could occur with buggy firmware. It is also capable of high current drive of a large quantity of LEDs (not yet tested!).

Schematic
A simple capacitive voltage doubler (charge pump) is used to create a high enough voltage for an ordinary power MOSFET. If the AVR output is stuck on, C3 will discharge through R4 and the MOSFET will eventually turn off.
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AVR output (top trace) and MOSFET drive (bottom trace)
The peak gate voltage exceeds 10 Volts and the rise and fall times are acceptable. The gate voltage rises to 8 volts within 100 nS and 10 volts within 500 nS.
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Circuit Board
Only two LEDs installed for now.
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maltman23
 
Posts: 134
Joined: Fri Jul 13, 2007 4:54 pm

Post by maltman23 »

Cool! Please post results when you try it out. From how far away can you turn off TVs?

Mitch.

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