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From: The Natural Philosopher <tnp@invalid.invalid>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: relay modules?
Date: Thu, 11 Apr 2024 09:38:47 +0100
Organization: A little, after lunch
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On 10/04/2024 11:50, Mike Scott wrote:
> Hi all. Two separate projects which will need a relay of some sort to 
> run from a Pi or similar.
> 
> I'm really looking for something plug-and-go rather than build-your-own 
> (especially item 2 below)
> 
> First is a dpdt relay to switch around 12-20 V at a couple of amps. spdt 
> are easy to come by; the only dpdt ones I've found are on aliexpress, 
> but their longevity is possibly open to question :-{
> 
> Second is something to switch mains safely - a full 13A to run a 3kW 
> heater. I've drawn a blank: best I can think of is to butcher one of 
> those wireless mains switch modules, which would at least provide a good 
> isolation gap :-)
> 
> TIA for any ideas.
> 

I built my own, and have spare PCBS. It has buffers to drive the relays 
, led drivers and a built in mains power supply to run the pi as well.


Only switches 10A at 230V though. However a purely resistive load like a 
3KW heater might well be OK


You can use *two* relays to do DPDT. :-)

Serious European made relays cost quite a bit.

Nearly all electronics these days comes ultimately from china.

Looking through my 'usual suspects' supply list it seems that solid 
state relays have overtaken big power contactors for switching high 
mains current.

What I would try to do is get a board with four low power relays on it, 
and use one to drive a big fuck off panel mounted *solid state relay*. 
Two more do DPDT.


Won't be cheap though...


-- 
There’s a mighty big difference between good, sound reasons and reasons 
that sound good.

Burton Hillis (William Vaughn, American columnist)