Re: Need 24-120AC/DC Voltage Detector

From: CFoley1064 (cfoley1064_at_aol.com)
Date: 09/28/04 

Date: 28 Sep 2004 03:44:33 GMT

>Subject: Need 24-120AC/DC Voltage Detector
>From: tbusky@prox.com (Ted Busky)
>Date: 9/27/2004 8:41 PM Central Daylight Time
>Message-id: <2d90e604.0409271741.6cf0fe14@posting.google.com>
>
>Does anyone have any ideas on how to create an opto isolator circuit
>that will respond to input voltages from 24V to 120V AC or DC? I would
>like to design the 7 inputs to my system so that I can accept any
>voltage in this range with minimal and preferably no jumper changes to
>account for the different sensitivities and rectificationn. The
>typical control voltages are 24VDC, 48VDC, 60VDC and 120VAC. If any
>changes of jumpers is required, I would like to do it with just one
>jumper for all 7 inputs.
>
>I know there are opto isolators like Opto22 that take from 3-32V and
>35-60V AC or DC and others that take 120VAC as inputs. I have looked
>at the HCPL3700 which is an opto with on board bridge and current
>source to the LED. And, I have looked at general purpose optos and
>added a bridge in front of them, but I have not come up with a LED
>driver that will accept all the voltages and have reasonable
>sensitivity in the noisy environment with long control cables (up to 1
>mile). Any single jumper solutions to change the sensitivity work fine
>if there is one isolator, but do not lend themselves to simply using
>that one jumper to handle 7 circuits.
>
>Thanks, for any ideas.
>
>Ted Busky
>

Hi, Ted. I used this circuit successfully a number of times for just what
you're looking to do (view in fixed font or M$ Notepad):

                                          VCC VCC
                                           + +
                                           | |
     4.7K 3W .------. H11L1 | .-.
       ___ | | ___ | | |
   o--|___|--o ~ +o---o--|___|-o-. .--o--. | |10K
             | | | 1K 1/2W | | | '-'
             | | +| V ~ | | |
             | | --- - ~ | H o--o-------o
             | | --- | ~ | |
             | | | 1uF 50V | | |
   o---------o ~ -o---o--------o-' '--o--'
             | | |
             '------' |
                                           |
                                          ===
                                          GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

http://www.fairchildsemi.com/ds/H1/H11L1-M.pdf

Use a 400V 1A full-wave rectifier. Get good quality electrolytics for best
results. This circuit will delay less than 1 full AC line cycle for turn off,
but it's very reliable, and doesn't have the annoying characteristic of false
turn-offs on line cycle transitions.

While not the cheapest possible answer, it's very reliable, and a lot less than
an Opto-22 module.

Good luck
Chris

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