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From: Gordon Henderson <gordon+usenet@drogon.net>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: relay modules?
Date: Wed, 10 Apr 2024 19:09:11 -0000 (UTC)
Organization: Drogon Towers
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In article <uv5qtf$te0a$1@dont-email.me>,
Mike Scott  <usenet.16@scottsonline.org.uk.invalid> 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 :-)

I used a solid state relay to control an oven some years back - the
Pi's 3.3v output was good enough to fire the relay although it's LED
was rather dim.

The oven was only 2.2Kw though, but I used a relay rated for something
like 40 amps (that's probably chinese amps, but it never failed in the
5 or so years I used it near daily when I was running my small bakery)

For a 3Kw project (Atmega, not a Pi) I used one of the SparkFun "Beefcake" relays.
I think it did need a 5v signal though. You'll need a driver transitor from a Pi.

https://www.sparkfun.com/products/13815

I built that into a control system in a micro-brewery 'washing machine'
about 5 or 6 years back and its still running today.

Gordon