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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 10:34:35 +0100
Organization: A little, after lunch
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On 10/04/2024 20:09, Gordon Henderson wrote:
> 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
> 

Good find - the relay is available separately at a sane price.

I might try and source some

https://www.aliexpress.com/item/4001135871051.html

Looking to make up some boards with mains relays on and PI Pico Ws and a 
mains PSU to go into the backbox of a UK mains socket to act as smart 
sockets...



> I built that into a control system in a micro-brewery 'washing machine'
> about 5 or 6 years back and its still running today.
> 
That says a lot more than any ali-express recommendation.

> Gordon

-- 
“The ultimate result of shielding men from the effects of folly is to 
fill the world with fools.”

Herbert Spencer