Linear actuator automatic reverse polarity help

Help & Support Robot Parts
1

Hi Guys,

New to the forum and having bit of difficulty with a project.

I have a lifting frame attached to a 12v motorized linear actuator.
The actuator has built in non adjustable limit switches so when power is connected to the + and - the actuator extends and when i reverse the polarity it retracts.

Simple yes! but heres my issue.
I need it to do this automatically.

My set up is as follows.

230v temperature controller closes a n/o switch when temperature reaches a set degree.
When closed this n/o switch powers up a 12v power supply that has the actuator connected and also a set of fans on a temperature speed control circuit.
so when the 12v supply gets power the fans come on at certain speed and the actuator extends
when the temperature drops the controller opens the switch cutting power to the fans so they go off.
But this also cuts the power to the actuator so it stays extended

Anyone know of anyway I can get the actuator to retract on this setup.

The only other thing i have is a cooling switch on the temperature controller that could possible be used to reverse the polarity but need an automatic way of switching it over.

Any help greatly appreciated.

Regards,

evanm1978

2

Hi evanm1978,

Welcome to the RobotShop Forum. There are likely ways you can do that purely electrically with switches etc., though an inexpensive solution would be to use a microcontroller and relays. A microcontroller can read the temperature and send a signal to a DPDT relay connected to the actuator, causing it to extend. The microcontroller can also send a signal to a normal relay connected to the fans. You would leave the power supply always on. Once it has extended, the microcontroller would send a signal to stop, then retract. This obviously complexifies the setup a bit, but the end result would do as you described.

Hope this gives you some ideas,