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Re: Driving optocouplers

Cross-posted to 3 groups.

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"John S" <Sophi.2@invalid.org> wrote in message 
news:mq2f9s$9qs$1@dont-email.me...
> On 8/7/2015 12:52 AM, DaveC wrote:
>
> A VFD (Variable Frequency Drive) is usually designed to be an industrial 
> controller. It usually has isolated inputs. That is, the inputs for the 
> enable function is usually passed through an optocoupler inside the VFD. 
> Furthermore, those digital inputs usually accept dry switch contacts.
>
> If the manual recommends otherwise then ignore my response.

That has been my limiated experance with the VFDs.  Some of them have 
adapter boards that use optical isolators.

 Ran into that problem when the company I worked for was in a big rebuilding 
project.  The engineer had just used the solid state output of a PLC to turn 
on a VFD.  The VFD wanted a hard contact, so I used an interposing relay as 
a quick fix as it was the weekend and needed to get it up and running.

It is really difficult to say the resistance of a solid state device is so 
many ohms.  As pointed out is is the ammount of currrent it can sink and how 
low the voltage will go.

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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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