Re: relay modules?

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