Groups > sci.electronics.components > #5707

Re: Driving optocouplers

From	John Larkin <jlarkin@highlandtechnology.com>
Newsgroups	sci.electronics.components, sci.electronics.design, alt.engineering.electrical
Subject	Re: Driving optocouplers
Date	2015-08-07 07:17 -0700
Message-ID	<fef9sadugptme73df46bsod01kt8u4khj0@4ax.com> (permalink)
References	<0001HW.1B747F150001D9661112F83CF@news.eternal-september.org>

Cross-posted to 3 groups.

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On Thu, 06 Aug 2015 22:52:21 -0700, DaveC <not@home.cow> wrote:

>http://pdf.datasheetcatalog.com/datasheet/vishay/83725.pdf
>
>The output transistor of the 4N25 optocoupler is spec’d at max 150 mA (no 
>mention of on-resistance). I measure the resistance across the output 
>terminals with the input driven with 17 mA and I see a little over 110 ohms.
>
>This is going to operate the enable input of a VFD: 10 vdc high-impedance 
>digital input needs to be pulled to ground. I’m concerned whether or not 
>the 4N25 will do the job. With an on-resistance of 110 ohms, will this pull 
>the input low enough?
>
>Maybe I should be looking at another optocoupler? What spec is important look 
>for?
>
>Thanks,
>Dave

An SSR might be a better choice.


-- 

John Larkin         Highland Technology, Inc
lunatic fringe electronics

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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Thread

Driving optocouplers DaveC <not@home.cow> - 2015-08-06 22:52 -0700
  Re: Driving optocouplers Tim Wescott <tim@seemywebsite.com> - 2015-08-07 01:08 -0500
    Re: Driving optocouplers DaveC <not@home.cow> - 2015-08-06 23:16 -0700
      Re: Driving optocouplers John Robertson <spam@flippers.com> - 2015-08-06 23:53 -0700
        Re: Driving optocouplers upsidedown@downunder.com - 2015-08-07 13:03 +0300
      Re: Driving optocouplers Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2015-08-07 08:21 -0400
  Re: Driving optocouplers John Larkin <jlarkin@highlandtechnology.com> - 2015-08-07 07:17 -0700
  Re: Driving optocouplers John S <Sophi.2@invalid.org> - 2015-08-07 09:29 -0500
    Re: Driving optocouplers "Ralph Mowery" <rmowery28146@earthlink.net> - 2015-08-07 11:59 -0400
      Re: Driving optocouplers John S <Sophi.2@invalid.org> - 2015-08-07 11:17 -0500
  Re: Driving optocouplers WangoTango <Asgard24@mindspring.com> - 2015-08-07 17:59 -0400
    Re: Driving optocouplers M Philbrook <jamie_ka1lpa@charter.net> - 2015-08-07 18:49 -0400
      Re: Driving optocouplers WangoTango <Asgard24@mindspring.com> - 2015-08-10 17:42 -0400

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