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From: Richard Rasker
Subject: Re: high voltage input
Date: Sat, 21 Dec 2002 21:03:26 GMT
Organization: de Kooi Internetdiensten
NNTP-Posting-Date: Sat, 21 Dec 2002 21:03:30 +0000 (UTC)
X-Newsreader: Mozilla/3.0 (compatible; StarOffice/5.2;Linux)
> How can i get an information from a 55VDC line. I need to connect the =
> to a cmos IC. What are my preferences and what do you prefer?
> 1- Dividing voltage with resistors and protect the IC with a zener?
Simplest & cheapest solution. It might also be a good idea to throw in a=
small capacitor to ground for extra noise & interference suppression.
> 2- or using an opto coupler?
Safest and most interference-proof solution, no direct (galvanic) contac=
between the higher voltage and the CMOS circuit. Only marginally more=20
expensive than solution # 1. Of course the 55 volts must be able to=20
source at least a milli-amp or so to drive the opto-coupler.
> 3- Are there any ic's which accept high voltages directly?
Not in standard, off-the-shelf CMOS types.
> I'm looking for a cost effective solution and also reliability and=20
> is important.
I'd say go for the opto-coupler solution. Whenever I need to exchange=20
signals between two completely different circuits, I try to keep them as=
much separate as possible, which in most cases boils down to using=20
opto-couplers or, in the case of audio, transformers.
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