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I have the schematic for an 8 channel 24V to 5V optocoupler board I purchased. It uses the EL817.

My input is an open collector input pulled up with 10K to 5V.

I can't drive it to gnd to trigger my input. It only goes down to 1.79V.

I would like to upload the schematic and my load if I can.

Thanks

JRE
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VIC
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  • Is your board something like this? https://i.imgur.com/dYahUoa.jpeg. You might like to show us a photo or the link to your board. – tlfong01 Jan 11 '21 at 07:17
  • Ah, it a a little bit confusing. You seem to have mixed up input with output. I guess the following is what you are doing: (1) The board consists of 8 channels, each of which is EL817 based. (2) Each input is open collector with 10K pulled up to 5V. (3) Output is perhaps open collector and also pulled up to 24V (not sure), (4) Not clear why you cannot "drive" input to ground. Perhaps you can give us a link to your board, or show us a photo. Cheers. – tlfong01 Jan 11 '21 at 07:19
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    The module is similar to the jpeg just with leds on input and output. – VIC Jan 11 '21 at 08:12
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    How do I provide a link in my comments to the module and schematic? – VIC Jan 11 '21 at 08:13
  • (1) I guess the LEDs are status indicators: one LED for input, another for output. (2) To upload images when editing your question, you can click the editing menu's image icon (showing "a sun and a mountain") and then drag/drop you image (for me, from my PC Win10 directory). – tlfong01 Jan 11 '21 at 08:15
  • https://www.ebay.com/itm/2Pcs-4Bit-Optocoupler-Isolator-5V-to-24V-PLC-Signal-Volatage-Converter-Board/393051518463 scroll down for schematic – VIC Jan 11 '21 at 08:21
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    I am trying to take a 13.8v or 0v input and convert it to +5v or 0v. The input of the circuit I am trying to switch between +5v and 0v is just a collector pulled with 10K to +5vcc and the emitter is connected to gnd. When the EL817 goes low it will only drive it down to 1.87 v ???? – VIC Jan 11 '21 at 08:37
  • Ha, your board is very flexible and can set (1) input signals as common anode or common cathode, (2) differential or single ended, (3) 3V3, 5V, ...24V control/logic level. SUGGESTION:I would suggest you to configure the following: 5V on both sides, singled ended, common cathode． – tlfong01 Jan 11 '21 at 08:46
  • You might like to refer to Appendix E of my answer to the following question to see how my test config is (1) 5V in, 5V out, (2) Input single ended, (3) status/load LED common Cathode. How can I test a TLP582 optocoupler? https://electronics.stackexchange.com/questions/541080/how-can-i-test-a-tlp582-optocoupler – tlfong01 Jan 11 '21 at 09:12
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    Why can't you upload it? What's stopping you? – Andy aka Jan 11 '21 at 09:50
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    the title of your post should be about an electronics problem, not about the usage of this website ... site usage questions belong at https://electronics.meta.stackexchange.com/ – jsotola Jan 11 '21 at 17:10

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