Digital input chips, I am looking for any.


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  1. #1
    Join Date
    Feb 2005
    Location
    Holmfirth England
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    Question Digital input chips, I am looking for any.

    Hi,

    In the past I have used the good old 2803 octal driver as inputs to a pic where space was too tight for using opto isolators.
    This proved to be problematic, interference wise, due to the darlington inputs needing hardly any current to drive them.
    See the schematic.

    I am looking for chips that will take 8 inputs, at preferably 24V, and turn them into 5V EMI proof outputs.
    I'm not having much success. I have found one that does this but only with serial output, not individual output lines.

    Regards
    Bob.
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  2. #2
    Join Date
    Oct 2005
    Location
    Sweden
    Posts
    3,286

    Default Re: Digital input chips, I am looking for any.

    Hi,
    I tend to use opto-isolators because of their ease of use and fairly low price (obviosuly depending on what performance you need). They also require a bit of current which inherntly makes them less sensitive to noise being picked up by long cables etc. TCMT4100/4600, LTV847/844 etc in SO16 package are my usual goto-parts. The PS2841 gives you four channels in a little 12-pin BSOP package - good looking device that - just stumbled across it.

    As I was looking around I found the ISO1I881T which claims to be an Isolated 8 Channel Digital Input with IEC61131-2 Type 1/2/3 Characteristics. I haven't looked at the details but might be worth to take a look at. Not cheap though...

    Let me know if you find anything suitable!

    /Henrik.

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