I'm a bit overwhelmed by the sheer amount of variations in optocouplers and since I've never used one before in any project I don't really know what criteria to look out for.
A colleague of mine suggested that I should replace the relays in my circuit with optocouplers as they are much cheaper and also smaller in size. I agree with him once I looked into it, but unlike relays, I'm very unfamiliar with optocouplers.
I have this schematics in which I use relays to enable/disable a parallel resistor.
From my understanding, if I were to use optocouplers I could get rid of the TPIC6C596, which I only need due to the high current draw of the relay.
So for this output-schematic I figured I could use this LTV-847 which would replace 4 relays at once.
But there were many other options to choose from and I just feel like I'm making a wrong choice because the above was simply the cheapest 4 channel chip that I found.
It's a simple circuit without much timing constraints, so any optocoupler that uses less mA than a relay and handles 24V could work.
For relays it was a bit easier, because I needed the smallest, cheapest 5V relay that I can get, which narrowed down the search quickly.
But with optocouplers pretty much all of the options are cheaper than the relays, are smaller and also use less current...
Would this circuit produce the same result as the relays?
Is my optocoupler choice fitting for the scenario, given that I have 24V on the input module and 5V on the control side. Basically just requiring a "switch" solution but in a smaller form factor.
Regarding my schematic:
Originally I used relays because I knew they don't produce a voltage drop on the output.
However, from what I've read, optocouplers do produce voltage drops because of the phototransistor used.
But since I'm unfamiliar with the component itself I didn't know how I could best reproduce the result of a relay with an optocoupler, meaning I can get the ~24mA needed on the output side.
The relay simply creates a parallel resistor, so the total resistance is around 1K ohm.
Would I need to lower the resistance of the output resistor R3 or are there optocouplers with identical results as relays?