Linear actuator wiring

[Dennis RaynerParticipant @dennisrayner52782]

I'm about to buy one of these **LINK** to operate a point but I want to put a switch by the side of the track from each direction so I can switch the point when approaching from each direction. I wondered if anybody could confirm if this is feasible and, and if so, what type of switches and wiring I would need?

[Dennis RaynerParticipant @dennisrayner52782]

[EmgeeParticipant @emgee]

Hi Dennis, the write up says it has inbuilt limit switches but no other connecting info.

The limit switches will clearly stop the travel but write up does not provide detail of contact arrangement to enable reversing.
Usually applying a reverse voltage will reverse the travel but if the out limit has opened an additional closed contact would be needed for the reverse voltage connection

Perhaps the limits are connected so when power is on the unit will cycle between IN and OUT by reversing voltage and you will have to switch the power off at the desired position.

When the operation procedure is known it will only require a simple circuit to provide what you want.

Emgee

Edited By Emgee on 07/01/2018 17:43:27

[Brian Sweeting 2Participant @briansweeting2]

I know this is an American site but you can get remote controls for those actuators which could do away with a manual switch.

Download their pdf catalogue for more info. **LINK**

No connection with this product.

[Les Jones 1Participant @lesjones1]

I can't see any mention of limit switches in the Ebay advert. It is almost certainly a permenant magnet DC motor whose direction is reversed by reversing the supply polarity. If it does have limit switches they wil probably have diodes in parallel with them so each one only prevents movement in one direction. If it does not have limit switches you could use micro switches. (Each with a diode in parallel) You would just need a DPDT swich to control the direction.

Les.

[Dennis RaynerParticipant @dennisrayner52782]

Thanks very much for the replies – after overnight deliberation I have decided to forget the 2 switches and go with this **LINK** Only time will tell if that is a good decision or not. Thanks again for your helpful comments.

 

Edited By Dennis Rayner on 08/01/2018 16:40:33

[Clive FosterParticipant @clivefoster55965]

I've seen several of that sort of actuator and all had travel limit switches with diodes in circuit as described by Les to simultaneously stop movement before reaching hard end stops and enforce motor reversal before things can move again. Being a DC motor simply interchanging + and – connections reverses the drive

Important to be careful what you hook them up to as they are pretty powerful. The one in the first link claims 165 lb thrust which can do serious damage if something gets caught up between the thrust end and a firmly fixed object. My experience with similar devices suggests the rating is conservative.

Drive end of the screw seems to be the weakest link. Diameter is quite small, usually with a key way, drilled hole or flat further reducing the size. All the ones I've been asked to fix were sheared off there.

Clive.

Edited By Clive Foster on 08/01/2018 17:00:05

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