Michael Karas wrote:
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It is also my honest opinion that the ideas of driving LEDs off some other supply is an old fashioned idea from old engineers who used to deal with driving incandescant bulbs at 200 mA each or OLD LEDs that took 50 mA just to get a small blip of light out.

I use a similar circuit to pulse banks of LEDs with 150mA + currents at moderate duty cycles for VMS displays. You cannot drive these LEDs from a 5V rail. Period. What Chris has made is turning into a very neat little tutorial on driving moderate loads from an 8052.

Also it is rare these days to have systems with dozens of LEDs. Almost always an LCD is used instead.

Err. Ask Erik about that - he designs things like Bus display panels. So do I. LED matrix displays are pretty popular for many outside systems where LCDs just don't hack it.

Steve