PIC Single-Chip 4-Digit 99-Minute Timer 2014-05-19

[Mike - K8LH]

Mike - K8LH submitted a new article:

PIC Single-Chip 4-Digit 99-Minute Timer - A very low parts count 4-digit 99 minute timer design.

I'd like to present a relatively simple 4-digit 99 minute timer project. The low parts count design is a result of experiments with some very bright miniature 4-digit displays available from Sparkfun that come in red, green, yellow, white (all $1.95), and...

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[Mosaic]

Hey Mike...how do you handle the PC pin currents into the Display with no dropping resistors, does the blue display have a high Vf giving a lowered I?

 

[Mike - K8LH]

As mentioned in the article, I'm relying on the built-in resistance of the I/O pin FET drivers for current limiting.

The average current and associated brightness is affected by the Vf of the displays;

You'll find that the red, green, and yellow displays (Vf=2.1v) are a bit brighter than the white display (Vf=3.1v) and the blue display (Vf=3.4v).