dogman Posted October 23, 2017 Share Posted October 23, 2017 Not sure if anyone can help but there a lot of Boffins who may know where i can get a small relay board I need to turn a switched live into a N/O contact. I have seen a large relay in a holder that will do it as well as din rail version. What i need is a small board version where the coil input is 240v ( the switched live ) and the switched side is a N/O switch I have seen plenty that are switched using 5v or 12v Link to comment Share on other sites More sharing options...
Onoff Posted October 23, 2017 Share Posted October 23, 2017 Anything here any good: https://www.esr.co.uk/products/frame_interface.htm Link to comment Share on other sites More sharing options...
PeterW Posted October 23, 2017 Share Posted October 23, 2017 21 minutes ago, dogman said: Not sure if anyone can help but there a lot of Boffins who may know where i can get a small relay board I need to turn a switched live into a N/O contact. I have seen a large relay in a holder that will do it as well as din rail version. What i need is a small board version where the coil input is 240v ( the switched live ) and the switched side is a N/O switch I have seen plenty that are switched using 5v or 12v Just put an SSR in the circuit in series with the switch. Most only have a single switched pair so are N/O. Link to comment Share on other sites More sharing options...
Onoff Posted October 23, 2017 Share Posted October 23, 2017 (edited) 34 minutes ago, PeterW said: Just put an SSR in the circuit in series with the switch. Most only have a single switched pair so are N/O. He doesn't want it in series surely? The switched live to A1 of the relay coil and A2 to neutral. Does something like this tick the box? https://www.discountfiresupplies.co.uk/product/280/558/Easy-Relay-240V-Mains-Relay-(230V-AC-50_60Hz-Coil) Edited October 23, 2017 by Onoff Link to comment Share on other sites More sharing options...
PeterW Posted October 23, 2017 Share Posted October 23, 2017 In series an SSR pulls a tiny amount of power - it wouldn’t affect whatever is in the load circuit of the switched live. Link to comment Share on other sites More sharing options...
Onoff Posted October 23, 2017 Share Posted October 23, 2017 1 minute ago, PeterW said: In series an SSR pulls a tiny amount of power - it wouldn’t affect whatever is in the load circuit of the switched live. But if the SSR packs up so does whatever the switched live is going to? Link to comment Share on other sites More sharing options...
dogman Posted October 23, 2017 Author Share Posted October 23, 2017 4 minutes ago, Onoff said: Does something like this tick the box? https://www.discountfiresupplies.co.uk/product/280/558/Easy-Relay-240V-Mains-Relay-(230V-AC-50_60Hz-Coil) Edited 2 minutes ago by Onoff Yes that would work 1 minute ago, PeterW said: n series an SSR pulls a tiny amount of power - it wouldn’t affect whatever is in the load circuit of the switched live. Had a look for a 240v input version but all switch AC http://www.ebay.co.uk/itm/ChaoHe-Temperature-Contoller-4-Terminals-Solid-State-Relay-SSR-25-AA-P4N5-/222688351495?epid=1787173477&hash=item33d9429507:g:gEAAAOSw9mpZ7JOO This is an example. As most normally open control circuits use 10v to detect the NO/NC state how would this work with an AC/Ac ssr Link to comment Share on other sites More sharing options...
ProDave Posted October 23, 2017 Share Posted October 23, 2017 CPC do lots of relay boards http://cpc.farnell.com/search?st=relay board Link to comment Share on other sites More sharing options...
dogman Posted October 23, 2017 Author Share Posted October 23, 2017 @ProDave did look at CPC but could only find DC switching/control not ac switching Link to comment Share on other sites More sharing options...
ProDave Posted October 23, 2017 Share Posted October 23, 2017 All relays will be able to switch AC or DC. Their current rating for DC switching will be lower than for AC switching. Link to comment Share on other sites More sharing options...
dogman Posted October 23, 2017 Author Share Posted October 23, 2017 Found this relay. Probably just as easy to mount on a strip board http://uk.farnell.com/schrack-te-connectivity/rt334730/power-relay-spst-no-16a-250v-th/dp/2748015 Link to comment Share on other sites More sharing options...
dpmiller Posted October 24, 2017 Share Posted October 24, 2017 do you really need 16A? Oh, and do you only need one of these? I think some of the MVHR brands have multiple-in interface boxes. Link to comment Share on other sites More sharing options...
dogman Posted October 24, 2017 Author Share Posted October 24, 2017 No the amps are not the issue. I need only the N/O N/c switching. The link was the cheapest I could find. Link to comment Share on other sites More sharing options...
PeterW Posted October 24, 2017 Share Posted October 24, 2017 In that case use an SSR. It won’t care what you put through the switched side so a 10v BMS logic signal won’t cause any problem. Link to comment Share on other sites More sharing options...
SteamyTea Posted October 24, 2017 Share Posted October 24, 2017 I bought a couple of small relays, I think they are either open or closed. http://www.ebay.co.uk/itm/220-240V-AC-Coil-DPDT-Power-Relay-MY2NJ-8-Pin-w-Socket-Base-FK-/232369299384?hash=item361a4a1fb8 Link to comment Share on other sites More sharing options...
dogman Posted October 25, 2017 Author Share Posted October 25, 2017 On 24/10/2017 at 10:20, PeterW said: In that case use an SSR. It won’t care what you put through the switched side so a 10v BMS logic signal won’t cause any problem. Thanks Peter will look at SSRs. Any idea as where i can get a couple cheapish Link to comment Share on other sites More sharing options...
dogman Posted October 25, 2017 Author Share Posted October 25, 2017 @PeterW cancel last found these https://www.ebay.co.uk/itm/250V-SSR-100DA-SSR-40DA-SSR-25DA-25A-40A-100A-Solid-State-Relay-Module-Heat-Sink/112605169480?hash=item1a37ca8748:m:mg_NqrRPXW4x_FaUjacuugg Link to comment Share on other sites More sharing options...
dpmiller Posted October 25, 2017 Share Posted October 25, 2017 NO! they're 3-32v dc input. You need the 240v variety http://www.ebay.co.uk/itm/AC-AC-70-280V-240-280V-10A-4-Screw-Terminal-One-Phase-SSR-Solid-State-Relay/121749029973?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 or similar Link to comment Share on other sites More sharing options...
TerryE Posted November 3, 2017 Share Posted November 3, 2017 On 23/10/2017 at 21:03, dogman said: Not sure if anyone can help but there a lot of Boffins who may know where i can get a small relay board Out interest, what is your actual requirement? Viz what are you switching 230-240V AC, DC? What load? How are you planning to drive it? What sort of duty cycle are you looking for? What sort of MTBF? If you are using TTL drivers (e.g 5V Arduino) then here are loads on eBay and the Chinese suppliers, (e.g just Google AliExpress 8 channel relay) or you can get USB varieties which you can plug into an RPi USB port ... Or you can get the SonOff range of plug-in devices. Most have Songle relay cans on them (or clones which have a far lower switching life). For hobby stuff, I jus use the cheapo's at <£10 for an 8-port, and keep a few ports spare if one fails. Running something critical like your central heating is another story. I use reputable UK suppliers like RSS for this type of kit, but at a significantly higher price. Link to comment Share on other sites More sharing options...
Onoff Posted November 4, 2017 Share Posted November 4, 2017 (edited) On 25/10/2017 at 20:39, dpmiller said: NO! they're 3-32v dc input. You need the 240v variety http://www.ebay.co.uk/itm/AC-AC-70-280V-240-280V-10A-4-Screw-Terminal-One-Phase-SSR-Solid-State-Relay/121749029973?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 or similar YES! The SSR-40-AA variant, picture 15 at @dogman's link looks to be ok. It's 80-250VAC input. Love the rip off of the RS logo! Edited November 4, 2017 by Onoff Link to comment Share on other sites More sharing options...
dpmiller Posted November 4, 2017 Share Posted November 4, 2017 Ah yes, the AA variant. Gotcha. Still well worth pointing out how important it is to confirm the input as 3-32dc is much more common. Oh and an anecdote from me- those Fotek relays are crap. By various means I've had a number of them recently and the failure rate (either DOA or at well under rated load) is near 50%. Baseplate feels like chromed plastic, really light. Those blue labelled ones (and I've seen'em with a couple of different brands) are much more heavily built and I'm yet to have an early life failure. 1 Link to comment Share on other sites More sharing options...
dogman Posted November 4, 2017 Author Share Posted November 4, 2017 @TerryEI have a fan coil that has an RS485 control system. I need to switch a pump on and off to feed the fan coils. As i don't want to use two different control systems the company recommend using a relay switched by the switched live in the fan coil to drive the pump and provide a N/O switch for the heat pump. As they will be mainly used for cooling there is no buffer vessel in the feed when in cooling mode so there is a need for the N/O As i may use more than one fan coil i understand that SSR don't like being in parallel with each other so may stick with relays Link to comment Share on other sites More sharing options...
TerryE Posted November 5, 2017 Share Posted November 5, 2017 57 minutes ago, dogman said: i understand that SSR don't like being in parallel with each other Eh? How? There is also a fundamental difference between resistive and inductive loads in terms of the power and peak current in back EMF on circuit make/break. The power of the device is the other key issue. After some debate here on the forum, l decided to use DIN mounted Crydom SSRs which can be driven by a TTL GPIO. One of the main advantages with this approach -- apart from the simplicity -- is that my sparky is happy to wire and certify the 240V side since these just look like MCBs to him. The whole system is working just as I planned, but that is the subject of a separate overdue blog post. Link to comment Share on other sites More sharing options...
PeterW Posted November 5, 2017 Share Posted November 5, 2017 20 minutes ago, TerryE said: [...] sparky is happy to wire and certify the 240V side since these just look like MCBs to him [...] So I've got a slightly different issue that the MVHR boost is a no volt connection and we want a "fan" switch in the grid in the kitchen. So I've agreed to let him connect to the "control box" with a 240v switched live that will then switch an SSR to give me the no-volt connection for the fan boost... Link to comment Share on other sites More sharing options...
dogman Posted November 5, 2017 Author Share Posted November 5, 2017 @TerryEIts just something i read when looking at SSR's I would rather use SSRs as they are cheaper than the relays and probably a lot better. They can be sited inside the heat coil so the wire going back to the plant room is volt free Each SSR or relay would have its own totally separate 240v switched live input. then the two N/O sides would be wired in parallel to each other to a single zone underfloor heating controller as if it was a thermostat. In effect calling for heat. The controller then fires up the pump and provided a volt free for the heat pump This is the cheapest and easiest for me to do. I all ready have an old single zone controller that is brand new but been sat in my garage for a couple of years Link to comment Share on other sites More sharing options...
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