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.
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.
Circuit Board
Only two LEDs installed for now.
MOSFET LED Drive (eXperimental)
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Please be positive and constructive with your questions and comments.
Please be positive and constructive with your questions and comments.