I need a way to turn off/on about 20 relays or FETs using RS-232 codes. (I do not want to program a generic microcontroller, I want a dedicated device that is designed to do switching only.) I notice that there products called "relay controllers" like this: https://store.ncd.io/product/rs-232-8-channel-dpdt-relay-controller-with-serial-interface/

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However the problem with this is that it has the relays built into it. In our case, which is a hi-fi audio application we are using specialized low-noise relays, so we need a board that kind of does what this does, take RS-232 codes and turn switches off and on, but does NOT have the switches or relays on the board. Is there such a thing, and if so what is the terminology that is used for it?

Once again: I DO NOT WANT TO PROGRAM ANYTHING and I do not want to use a programmable device. I need a module type that accepts codes or messages via RS-232 and turns lines high or low accordingly. What is this called?

I have tried terms like "rs-232 switching controller", "switching board", "switching IC", "relay controller", etc, and the closest thing I can get is stuff like the below with the switches built into the board.

  • \$\begingroup\$ how do you define "low noise"? \$\endgroup\$ – Tony Stewart EE75 yesterday
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    \$\begingroup\$ You can just buy what you want and replace the original relays with your low-noise audiophile relays. But if you don't want to program anything, how will you be able to send anything from any device to your ready-made relay box to control it? \$\endgroup\$ – Justme yesterday
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    \$\begingroup\$ >>> I need a module type that accepts codes or messages via RS-232 and turns lines high or low accordingly. What is this called? $$$$ "Obsolete" ;) $$$$ RS-232 was on the way out 20+ years ago. Why are you using it and not USB???? \$\endgroup\$ – Kyle B yesterday
  • \$\begingroup\$ @KyleB RS-232 is the standard in high end audio and we are already using RS-232 to control other pieces of audio equipment? Any more X-Y questions? \$\endgroup\$ – Tyler Durden yesterday
  • \$\begingroup\$ Funny, the pictured board uses a generic PIC microcontroller. Anyway, buy that one and remove the relays. Bridge the output to the terminals and connect that to your own designed relay board. \$\endgroup\$ – Passerby yesterday

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Figure 1. A search for "rs232 digital i/o module" throws up plenty of likely contenders.

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    \$\begingroup\$ Worth mentioning that a simplest microcontroller solution will do the same but for much cheaper, so the "I don't want to program anything" approach might be worth reconsidering. \$\endgroup\$ – Eugene Sh. yesterday
  • \$\begingroup\$ @EugeneSh. It might also simplify the programming on the PC side. The manual for one we've used in an industrial environment (16 I/O) is almost 400 pages. \$\endgroup\$ – Spehro Pefhany yesterday
  • \$\begingroup\$ @SpehroPefhany Right. Depends on the use though. These are usually coming with some awkward GUI with buttons you can use to toggle the outputs \$\endgroup\$ – Eugene Sh. yesterday
  • \$\begingroup\$ @EugeneSh. Yes. We supplied own GUI and some Python code to make it automate the desired functions. I think the GUI and associated library was most of the work. Thank goodness they didn't go with LabView. \$\endgroup\$ – Spehro Pefhany yesterday

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