Sensors for pool cover (or anything on wheels) position

Hardware Home Automation
1

I am looking for a solution to determine the position of a motorized pool cover, before beeing able to automate it’s opening and closing cycles.
This solution would be placed in the concrete, under or in the rail of the cover, on the path of the wheels. So, needs to be IP67 and wired.

I thought about using microswitches to put under the path of the wheels, but the small contact size (<2cm) makes it less than ideal.
Another possiblity would be to have some hard area placed on springs which would close/open some dry contact. But I haven’t found anything close to this.
Does anyone knows about some kind of “plate/slab” with dry contact that I could use?
Any other idea which would help is welcome!

2

What about Reed sensors? Can you attach the magnet part to the end of the cover?

Perhaps a sonic range sensor could be used. I’ve seen both used in garage door position sensors.

3

I’d be looking at the kind of magnetic contact used for intruder alarms on rollershutter doors. They are, uh, “robust”.

4

Great idea the reed sensor. I should have thought about it…
I will need to find a magnet powerful enough to cover the ~5cm range, but at the same time not too strong so it doesn’t trigger too early.

That could be a good option for it’s robustness but from what I found it is only with close range.

5

Well. you may have to choose the “it”
Here’s CQR brand with 50mm max gap to “close”
https://www.cqr.co.uk/wp-content/uploads/2015/08/RS002ALI.pdf

These things are big and clonky, I don’t know what sort of mounting options you have. You’d really want to handle one or look at one in someone’s loading dock to get an idea.
You’d generally secure the contact part to a flat surface - you can drive a forklift over it, and leave it in a puddle. (The short armoured flylead can be taken to a waterproof box nearby).
The moving magnet is designed to stick out proud of the “door”, and have a gap when closed (as the doors typically have a squishy bottom seal).

6

Indeed, it is bid and clonky. I will need to see how I could mount it but not sure it is an option…

But thanks for pointing it out, I might use it for the gate.

7

Have you looked at industrial limit switches, which can be weatherproof and be fitted with long roller or plunger actuators?

8

Yes, it was my initial thought.
Something similar such switch could be an option, but I had three concerns: 1- integration is not the easiest, 2- it will be standing on the floor so dirt might clog the moving parts and 3- it is definitively not the cheapest way…