Re: solid state relay??

On 01/08/2025 21:47, Theo wrote:

Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:

On 01/08/2025 14:49, David Higton wrote:

If you can drive relays momentarily but not continuously, consider
bistable relays.

>
I do have some, bought for another part of the project. But at IIRC ~£7
a pop, they're not cheap: I need 8.

 I'm seeing things like this for searches of 'magnetic latching relay' for £1
a relay or £2 on a board with GPIO inputs:
 https://www.aliexpress.com/item/1005009593982672.html

"Sorry, this item's currently unavailable in your location.".

https://www.aliexpress.com/item/1005005163980370.html

That looks a good possibility, thanks. I do see that ali offer these on a module as well, with added components. I'll have to check the datasheet, but I imagine the pico won't drive the relay coils directly. It's also £4 a pop on a module. x8.

 No experience, but I think there are some boards which do the latching
digitally and then drive a conventional relay.  These ones look like the
real deal.
 You have to hold the latching inputs for a certain length of time - not sure
what happens if you exceed the rated time, I don't know if there's a danger
of burning something out (railway modellers will perhaps be all too familiar
with this idea from motorised points).

So I imagine. I bought a board that charges a big capacitor, then uses that to run the point motor, automatically cutting off the charging power when current is drawn. Then you can't burn them out. The currents are really quite large: a SEEP motor seems to be about 2 ohms for the coil, and I'm running from a 19V psu, so we're talking around 10amps. For that, I'm using some overly beefy mosfet modules. A much simpler problem than steering power to the tracks. I have a pico-based control board to control 6 points with USB to a desktop pc. Works well in testing.
I'll give the relay modules a bit more thought. Thanks.
--
Mike Scott
Harlow, England