My "point" was to share an idea, something that's been increasingly harder and harder to do anywhere around here anymore, but certainly not to be the last word on anything.
Maybe I should have done more like the textbooks and avoided specifying any values for any of the components.
Maybe we should all shut the hell up and leave everything to the tender mercies of Mr. Drive-by and the MAX7219 salesman.
What are " Mr Drive-by" initials ? ( I know who the 7219 Salesman is.)
I think a 500 ohm resistor and a 3 k - 5 k trim pot would work for the BD442 PNP transistor base resistor. ( the OP DID say which PNP he is using. It's a TO-128 transistor package and collector current rating (4A).
)
gpsmikey:
They may even have a built in switching regulator in them - look at the LED tail lights on cars these days - when they are on, turn your eyes so they scan across the lights and you will notice they are being strobed to maximize the apparent brightness of them.
I don't think that's why they're strobed. In the old system, the bulbs have two filaments, one for the running light, and one for brake/turn. With LED's there are not two sets of lights, just one. They just run at low intensity with PWM until they have to indicate a brake/turn, then they come on solid.