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Two things?

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Scarr

Member
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

:p
 

TheAnimus

New Member
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

Member
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
 
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