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verobel
11-17-2006, 04:32 AM
Fellow Stampers..

Could you suggest to me how to isolate analog inputs and outputs going into a stamp microprocessor. I saw an analog isolation chip ps8601 but couldn't quite figure out how it· works.. it seems to require pulse input.. not an analog input. Has anyone done this?

Thanks, John

Chris Savage
11-17-2006, 04:53 AM
Optical Isolation is a common way of isolating signals.· This also applies to analog signals as the output can be configured to run into an ADC.

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Chris Savage
Parallax Tech Support

verobel
11-17-2006, 06:02 AM
Ya Thanks Chris.. I know what analog isolation is.. but how do we do it.. ie what chip do you suggest say for 1-5V input analog signal going to an AD0831 going to the stamp? Or on the out put side: stamp to D/A to 1-5V.. what would you use there? Is there a output side chip you recommend that has built in current boost (thus reducing the need for extra downstream circuits)?

John

ps I think the discrete I/O points are easier to setup. But the analog opto isolation chips are not always easy to understand. eg. ps8601 (~2) and have different techniques BB iso124. Ideally we would like to run every thing off a nominal 5V supply.

Chris Savage
11-17-2006, 06:36 AM
John,
·
·· I don’t have any part numbers right off the top of my head except old-school parts.· I used to use the TIL111 in my old circuits.· Technology has come a long way since then and there are opto-isolators which would be better suited to a linear analog signal into an ADC.· In fact, I posted a link to a website a couple of times where a customer did this very thing to monitor the individual cells (batteries) on his electric car.
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·· Each battery was tied into an opto and its output was fed into an ADC.· The output was configured so that they could each be calibrated.· It was a very clever design and may help you out.

http://genki.home.ionet.net/BattMon/BattMonArticle.html

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Chris Savage
Parallax Tech Support