bullen
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High Wattage Remote Relay

Thu Nov 29, 2018 10:22 pm

Just before I start I know this is a touchy subject, specially with British that have very stringent electric security requirements so I will try to thread as carefully as I can.

I'm trying to build a remote relay that can support >1500W AC.

Now before you light this thread on fire, I know this is really really stupid, but I don't have any choice.

So if we just try to discuss this knowing it's incredibly stupid?

Respectable places obviously don't sell these.

All the ones I found have the high voltage leads on the PCB.

Does anyone know any serious attempt at building something like this.

Preferably with the high voltage relays having the leads on the actual relay component itself.
Last edited by bullen on Thu Nov 29, 2018 10:45 pm, edited 2 times in total.
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jdb
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 10:29 pm

1500W of what? Lighting? Motors? Heater elements?
What's the duty cycle - 10 times in 15 minutes or is it going to switch some production line machinery that's operated hundreds of times per hour?
Rockets are loud.
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bullen
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 10:36 pm

Heater, on/off very rarely.

I really only found these so far:

https://www.bc-robotics.com/shop/raspbe ... relay-hat/

But I'm really concerned with their PCB and relay components, I'll probably loose the insurance using these.

Edit: wait found these now:

https://www.amazon.co.uk/Energenie-ENER ... ref=sr_1_1

Shame they use radio though... not very reliable.

Also really really wish they had a temp sensor on the HAT!
Last edited by bullen on Thu Nov 29, 2018 11:08 pm, edited 1 time in total.
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pcmanbob
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 11:02 pm

If you really want to do this I would suggest you will have to build your own setup.

I suggest you look to using an octal relay, with a 12v DC coil that way you can switch the 12v using a transistor circuit and the pi.

All the mains connections can be made on the base of the octal relay.

You can get octal relays with 2 or more mains rated contacts that you can connect in parallel to get the rating you need.
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davidcoton
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 11:10 pm

pcmanbob wrote:
Thu Nov 29, 2018 11:02 pm
You can get octal relays with 2 or more mains rated contacts that you can connect in parallel to get the rating you need.
That depends. If the issue is the current carrying capacity, contacts in parallel is OK. If it is the switching capacity, since there will be some difference in the time of operation of the two contacts, one contact will end up switching ALL the power. In the absence of detailed product data that indicates an adequate switching capacity for each contact but lower carrying capacity, get a relay with each contact rated for switching (and carrying) the full load.

Commercial remote control adaptors are safer and easier if you can make the radio side reliable enough.
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bullen
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 11:19 pm

Ok, thanks for the input.

The last one I found apparently has some tricky setup because they ship them with the more advanced SPI remote.

The octal relays look like they are more what I'm looking for, but I wish they came with 5V and GPIO friendly amperage to operate.

Tricky this.
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pcmanbob
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 11:48 pm

No relay can be driven directly from the pi gpio, no matter what it's coil voltage is, you will always need a driver circuit of some sort.

With the load and voltage you want to switch you are entering in to the industrial world and 12/24v DC is a fairly standard operating voltage for control systems in industry.
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bullen
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Re: High Wattage Remote Relay

Thu Nov 29, 2018 11:54 pm

Sure, trying to think out of the box... like I only need to turn the thing ON remotely... so gravity could be my switch... Rube Goldberg etc. etc.

What is that smell? ;)

I ended up buying from this seller: https://www.ebay.com/itm/5V-Relay-Modul ... 2197456263

I'll probably not leave this unattended, but otherwise it's a good start for a lovely bonfire!
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PhatFil
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Re: High Wattage Remote Relay

Fri Nov 30, 2018 1:51 am

May i suggest you look at the esp826x based wifi controlled relay switches, the itead sonoff brand is even designed with reprogramming expected with a serial programming header exposed on most pcbs.

flash with your own custom code written within the arduino ide, platform io or visual studio code.. etc... or use one of the public projects such as tasmota https://github.com/arendst/Sonoff-Tasmota/wiki. then all you need do is host a mqtt broker on your pi and publish the respective on/off control commands via wifi/mqtt to control your device.

the sonoff s20 uk is a 3 pin plug in wifi controlled socket with a 10a relay which needs NO mains wiring/modding whatsoever.

Earlton2
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Re: High Wattage Remote Relay

Fri Nov 30, 2018 2:04 am

I've pulled many a relay from old microwave ovens and furnaces. Much of these have the power lines on top as spade lugs while the low voltage coil lines were soldered to the board on the bottom. Early on the coils were 12V but of late they are more likely 24VDC. In either case I have used a 2N2222 transistor (40V 600mA) to drive them from a logic line. An example from my 'stock' is an OMRON G4W 11123T-US with a 24VDC coil and 15A 250VAC Normally Open contacts.

Should you need a little more isolation between the control and 'it' you might consider installing an onto-coupler in the control circuit. A 4N35 wouldn't likely give you enough current to run the relay but it could easily drive a 2N2222 or equivalent as a Darlington Pair.

bullen
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Re: High Wattage Remote Relay

Sat Feb 23, 2019 1:56 pm

BTW FYI IKEA has made this so panic over.

Edit: https://www.ikea.com/se/sv/catalog/products/90356166/

But you also need https://www.ikea.com/se/sv/catalog/products/40337806/

Edit2: Also has motion detector: https://www.ikea.com/se/sv/catalog/products/30383511/

But I don't know if it can be paired with the power plug via the app...
Last edited by bullen on Wed Feb 27, 2019 8:04 am, edited 3 times in total.
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stevecobb76
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Re: High Wattage Remote Relay

Wed Feb 27, 2019 3:28 am

maybe a pi controlling a servo from a separate power source
and servo push/pull a mechanical switch

no electrical contact needed. less chance of shorting out your pi with a power spike or surge

JohnsUPS
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Re: High Wattage Remote Relay

Wed Feb 27, 2019 11:51 am

I'm trying to build a remote relay that can support >1500W AC.
So long as you're not switching an inductive load, and a heater isn't, then look at a contactor.
A contactor is basically a relay on steriods.
Looks like you're only switching about 12.5A (@120V), or a bit over 6A (@240V), but you want to over rate the contacts a bit (maybe 20-50%) for longevity/reliability.

Now, in order to switch the contactor, you will need to connect a suitable relay to the Pi, and there are many boards/hats out there with relay ratings high enough to do this easily. Yes, you are basically switching one relay with another, but the relay connected to the Pi only has to switch the coil in the contactor. Maybe an amp for the contactor coil. It is the contactor that has the serious contacts to handle the current you are talking about and do the heavy lifting.

Also, you do not want to get a multipole relay and connect the contacts in parallel. To the naked eye, the contacts connect at the same time, but they don't. The contact that touches first will take most of the current and wear the most. A contact used in this manner probably isn't up for the job by itself, or you wouldn't have connected them in parallel to begin with, therefore it is a problem waiting to happen.

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