PIC: CA 7Seg from 12V

hantto said:

Hello!

In order to save regulator dissipation, would this work? To turn segments on and off the TRIS register would be used. Doesn't that turn the pins from sink/source to high impendace and vice versa?

Anything I didn't think of?

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Nigel Goodwin said:

hantto said:

Hello!

In order to save regulator dissipation, would this work? To turn segments on and off the TRIS register would be used. Doesn't that turn the pins from sink/source to high impendace and vice versa?

Anything I didn't think of?

Click to expand...

Yes, the PIC pins have protection diodes from the pin to Vdd and to Vss, so the bottom of the 330 ohms will never go above 5.7V, so all segments will be permanently lit. You could do it with open-collector driver transistors between the PIC and the resistors.

Click to expand...

eblc1388 said:

Or fit a 7V zener diode between 7-seg LED CA and +12V.

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eblc1388 said:

For a certain amount of LED current, the dissipation has to go somewhere. If it is not in the regulator, then it will be in the transistors, resistors or zener.

So in a sense reducing dissipation is not possible. Or one can try PWM on the output PIC pins.

Click to expand...