Two things?

[Scarr]

Hi,
I have two questions, first,

I want a easy solution to isolating a I/O pin on a pic from the nasty outside world, the only problem is the voltage could be anything! (well OK realistically 5v-300v DC) now I know about opto-isolators but canot figure out how to get the limiting resistor so it works with a wide voltage range?

Any Ideas, I was looking for a I2C opto-isolated I/O chip as this would be great, but can't see one :O(

Second, anyone seen any IC / code for reading files to and from a CF memory card, again, I'm looking for a total solutions here, baisically a IC that I can drop on the board, issue commands and it stores data in PC compatible files.

Thanks

 

[TheAnimus]

i might be wrong (i have a tendancy with the non-digital stuff) but most opto-isolators i have used (cheap ones ) don't tend to take input voltages of 300v. I think that clamping diodes would be the best way to "chop" the voltage down a bit, assuming that the input voltage dosen't have to be preserved.

 

[Scarr]

The HS H11N1

This chip from RS (www.rswww.com) has this spec

Isolation voltage 3750V r.m.s.
Common mode rejection 10 000V/ms

So being a little new I thought "how the hell do I accomodate that range!" but it sounds like your on the right track from what little knowledge I have about electronics. Any ideas of a clamping diode that would do it, I think between 12v-60v is more realistic but as it is a automotive alarm and I want to stop people trying to break it by using a electric welder on the body work to disable my little alarm. I was simply trying to cover all eventuallities :O)

Thaks for the reply

 

[Scarr]

Oops, chip name in subject above not in message

Thanks