pardon the noob question (though I have a EE degree back in the day, it's been a long time).

Let me ask this simply, then explain my use case below. I am wanting to use several existing CAT5 cables with a simple manual switch on them to activate individual AC outlets. I'm thinking that something like the SainSmart SSR board should do it. However, all examples of using relay boards like that relate to computer controlled applications. I don't really need all that. I just want a remote low-voltage switch to kick on an AC outlet. If it matters, each outlet is only going to pull 20-50 Watts.

I'm thinking this should conceptually be okay for what I want. But... I don't know exactly how to hook it up. Would wiring a separate 5V DV supply to the switch and then to one of the input terminals on the relay board do the job? Would I need a limiting resistor? or is that built in? From the schematic, it looks like that's included and I'd just apply +5V to the channel input.

If this were something I could quickly buy and play with, I'd do that, but it looks like these things take 3 weeks to arrive and I don't see any option to return it. So, I was hoping someone could toss me some advice on this.

Here's the details on the use case. I'm trying to replace a whole-house stereo system with a DIY version. Each room has CAT5 run from the central location to a control panel in each room. however, those control panels are shot. So, rather than replace with a new set of panels which will just wear out and avoiding a more expensive remote-control (or even iphone) based system... I want to leverage the CAT5 in the room to just have a simple switch to turn on an outlet for a small amplifier which will drive that room's audio. Thus, each room can then independently kick on a small amplifier for that room (rather than a big expensive multi-room amplifier). Each zone is just going to have a 20 watt amp (possibly a 50 watt in a large room) so it's not a lot of power. but, I obviously don't want to try running the AC power to the amp's power supply via the CAT5. And, even though the amps have a 12V DC power supply which I could potentially run over CAT5, I think that's going to try to pull too much current. So, that's why I'm thinking a SSR or traditional relay is what I want to be using.

Further clarifications: I have one central hub (basement closet) where all wiring is routed. so, from that closet, CAT5 goes out one line to each room. Also, from that closet, a pair of speaker wires go out to each room. My plan was to use a distribution amplifier from an audio source to feed a series of small amplifiers--one for each zone. and I would use the CAT5 to simply kick on an outlet to activate power to that room's amplifier. The audio source is going to be something I can manage via iphone app (select audio stream, volume, etc.) so I just want something to control which rooms have the sound turned on. I know this is crude and simplistic. but, I don't need an awesome elegant system. I'm looking for cheap.

I hope that makes things more clear. Audio and power isn't really bouncing around the house... it's all centrally located. I just want to find a way to remotely "flick a switch" to kick on the amp for the room I'm in.

Any issues with doing what I want? Any other products I should be considering? I don't want to go spend $400+ for a commercial product and I don't want to go completely DIY (I can solder, but I don't really want to build an 8-channel relay circuit from scratch either).

much appreciated for anyone to help guide me before I order and waste time waiting for something to arrive which might not work.

  • \$\begingroup\$ I think that would work but I don't think we have all the data. There is a central location, Cat5 runs to a remote location, a switch at the remote location closes a relay back at the central location (?) which activates an outlet and an amplifier at the remote location. This is prewired? Meanwhile audio information is somehow being moved from the central location to the remote location? On the surface, it seems like a lot of back and forth. But like I say, I don't think we have all the elements. \$\endgroup\$
    – mikeY
    Nov 18, 2013 at 16:59
  • \$\begingroup\$ @mikeY -- ah. I see the confusion and I edited to hopefully provide more clarity. everything will be at a central location (audio source, distribution amp, amplifiers) since that's where the CAT5 and speaker lines all terminate. the switch on the CAT5 should activate an outlet down in the stereo closet, not within the room... each room's speaker lines originate in the closet. I hope that's more clear. thanks for your time! \$\endgroup\$ Nov 18, 2013 at 19:45

1 Answer 1


Yes, with the clarification I think that would work. Stereo closet has the mains power, one end of speaker wires and one end of a Cat5 cable. Remote location has other end of speaker wires and other end of Cat5. Low voltage power source (5-12v) applied to Cat5 in stereo closet, switch closed in remote location on Cat5 completes circuit and triggers relay, activating mains power to room amplifier. Input from audio source amplified by room amplifier and piped to remote location via speaker wires.

I think that you may want to consider a latching relay. A regular relay makes a connection when the coil is energized. You hook up the thing you are powering to the NO or NC contacts and when the coil gets power the thing you are powering is switched on or off as long as the coil is energized. A latching relay would allow you to leave the room amps on with the relay in a resting unenergized state. A regular relay is analogous to an invisible somebody standing there smashing down a momentary button for as long as you want the amp on, while a latching relay would be more the passive switch I think you have in mind.

Finding a suitable predone 8 channel, zero crossing, latching relay module could be a tall order. You may need extreme Google-fu or Digikey-fu. Or 8 1 channel models.


  • \$\begingroup\$ thanks a lot @mikeY. I understand about a relay. I was planning to just put a light switch at the end of the CAT5 and figure that the current required to keep the relay on was going to be neglegible power consumption. I'll research a latching relay. But, if I just had the switch running that low voltage current the whole time, it should keep the relay open. right? a big part of my question was also if anyone has used the SSR board i refer to above, if I can just throw 5 V across the input of the channel I want. I assume that's what the Arduino controllers send to the inputs. is that correct? \$\endgroup\$ Nov 18, 2013 at 20:51
  • \$\begingroup\$ Yes. An Arduino or other microcontroller is going to put <=5v at some milliamps on the relay. With no need for a microcontroller, you could select relays with 12v or 24v coils if you wanted. I have not used the board you linked to but those are popular boards and I have no reason to think ill of them. I think if your simple light switch just kept a 5v circuit closed and energized a relay coil the whole time it would work fine. It just seemed more elegant and long term to me somehow to figure out how to do it with a latching relay that wouldn't have to stay energized. \$\endgroup\$
    – mikeY
    Nov 18, 2013 at 21:04
  • \$\begingroup\$ thanks again @mikeY. much appreciated. I wanted to make sure I didn't need some sort of resistors in place to limit the current so I didn't blow it the first time I tried it... at this point... the whole system is far from elegant... I'm frustrated that the big-name multizone system we put in 10 years ago is pretty much obsolete since we can't replace their dead keypads. so, I'm looking to invest as little money in getting this running. If you have any similar boards I should consider, I'd be happy for the advice. I just stumbled upon this one and seems all positive feedback on it. \$\endgroup\$ Nov 18, 2013 at 21:12
  • \$\begingroup\$ I'm not making any warranties here. If you put 12v and 5 amps through a 5v 50 milliamp relay coil you are on your own on that one. Best of luck! \$\endgroup\$
    – mikeY
    Nov 18, 2013 at 21:29
  • \$\begingroup\$ thanks yet again. I'll do my best to be careful and have a fire extinguisher on hand just in case. :) \$\endgroup\$ Nov 18, 2013 at 21:35

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