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240v coil relay board


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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 

 

 

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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. 

 

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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 by Onoff
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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?

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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

 

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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

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  • 2 weeks later...
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.

 

 

 

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On 25/10/2017 at 20:39, dpmiller said:

 

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 by Onoff
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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.

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@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 

 

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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.

 

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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...

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@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

 

 

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