Advice wanted - controlling actuators-external limit switch-camper roof application

Thread Starter

Montee

Joined Oct 31, 2022
2
Hello from Australia!
Hoping for some help controlling 3x actuators on my camper's roof.
Non have any limit controls and all are operated manually via DPDT 20A switches. So 3 actuators = 3 switches.
Had experience with actuators over running their extended limit and jamming up.

So the design goal is to fit reed switch/magnets at the highest and lowest permitted reach and have reach control by cutting power at the ends - so to speak. Ideally I will end up with one DPDT up-off-down switch that controls all 3 actuators and sends them more or less in unison to the extent of their travel. They do track each other well and this isn't an issue so synching isn't required in any solution.
The diagram here is a start.

The reed switches are 0.5A vs. the actuators 15-20A (12V).
So I need a way to get around this.
Relays driven by reed switches?
Or is there a more elegant way?
Open and grateful for help.
Diagrams are good!
Thanks in advance.




actuator.jpg
 

dendad

Joined Feb 20, 2016
4,251
Have a look at micro switches instead of reeds as they can handle the current. Reeds will not.
Or use Polyswitches (re-settable fuses) with the diode across them and have the current rating low enough to prevent jamming but high enough to run. I've used Polyswitches and diodes in industrial control applications quite well.
For example...
https://www.jaycar.com.au/rxe250-pt...947e7d267a4b07c04bd2a32730f4e9&sort=relevance
These are only 2.5Amps and that will not be enough, but higher currents are available from RS Components, Element14 (Formally Farnell), X-ON, Mouser or similar.
 
Last edited:

Thread Starter

Montee

Joined Oct 31, 2022
2
Have a look at micro switches instead of reeds as they can handle the current. Reeds will not.
Or use Polyswitches (re-settable fuses) with the diode across them and have the current rating low enough to prevent jamming but high enough to run. I've used Polyswitches and diodes in industrial control applications quite well.
For example...
https://www.jaycar.com.au/rxe250-pt...947e7d267a4b07c04bd2a32730f4e9&sort=relevance
These are only 2.5Amps and that will not be enough, but higher currents are available from RS Components, Element14 (Formally Farnell), X-ON, Mouser or similar.
Thanks for input. Can't use microswitches due to physical constraints. Magnets will be embedded in actuator arm through round holes and reeds will be on brackets to sense as they go by....Polyswitches look interesting but odd - new to me...
 

dendad

Joined Feb 20, 2016
4,251
I do not use any fuses now. A Polyswitch ( that is a brand name I think) is a lot easier as they reset when they cool down.
If you need to go the reed way, have a reed operate a Normally Closed relay contact. Make sure you connect a diode in reverse across the relay coil to help prevent reed arcing.
I'm in Oz too :)
 

Sensacell

Joined Jun 19, 2012
3,098
Take the exact circuit you have now - replace the motor with the relay coil that simply switches the motor and you are done.
The switch must still reverse the polarity to the whole thing.

This just takes the heavy motor current off the reed switches.
 

MisterBill2

Joined Jan 23, 2018
13,778
If there is room on the actuator motors, and if none of the drive motion is subject to slipping, then a really elegant scheme would be UP/DOWN counters for each actuator. This could be a good place for one of those little micro computers. A few years back I did that with a single actuator system, and industrial robots do it with six axis all the time. The benefit is not needing to install and wire switches someplace. The scheme may not be workable, but it is worth a few minutes consideration.
 
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