Automotive Use

[Archangel]

Does anybody have a really elegant way to switch PIC inputs from12 to 24 volt sources, I'm thinking automotive, marine, or even aircraft sources, I was thinking voltage divider, but . . . is there a better way?

[Archangel]

I had to quote Homer Simpson on this one - Stupid question!
I guess that is what opto isolators and current limiting resistors are for , stupid me!
J. S.

[muddy0409]

One thing I have seen used, but not used myself, is to use 78L05 regulators with the input to the high voltage you want to detect, and the 5v output going to the PIC input pin.
Seems pretty good in theory, as any variations in the input will just be absorbed by the regulator. A bit better than voltage divider etc???

[Archangel]

In 1,000 years I do not belive I would have tried that! It sounds like a terrific
Idea, cheap, easy to implement, small footprint, I don't think it would be great on a real low power application but most automotive apps. are not low power!
I'm going to try it! THANKS ! ! !

I love it when creative people get together and swap Ideas!

Joe Stokes

[Acetronics2]

Hi, Joe

A simple opto-coupler ( 4 pins footprint for the TLP 620 i.e. ) ... will do it really nice.

And avoid ground interconnections too !!!

Alain

[Archangel]

muddy0409
Your idea to use LM7805 integrated circuit regulators is a GEM, it works well and it takes up way less room on the circuit board than an opto coupler, opto isolator and requires no resistor for the led as in the opto device, thereby making PC board layout a snap. Very innovative, Thanks Again! JS