Linear Actuator Cycling Circuit Diagram

Thread Starter

sayerdesign

Joined Feb 17, 2021
8
Hello, all.
Looking for assistance in finding a wiring diagram for my application.
I want to be able to tap a foot switch button and have a linear actuator extend, then retract. One tap of the button, one full cycle of extension and retraction.
I want to keep the circuit mechanical/analog. Relays and switches rather than some sort of digital controller.
Any help would be appreciated.
 

MaxHeadRoom

Joined Jul 18, 2013
23,125
Is this one operation, i.e. initiate FWD and auto retract, I assume the actuator has internal L.S and two conductor feed ?
What is the motor details?
 

Thread Starter

sayerdesign

Joined Feb 17, 2021
8
Yes, one forward and retract per tap of the switch.
External limit switches to trigger retraction and then stop.
Two conductor feed on actuator.
This is garage R & D for a product to possibly market, so no particulars at this time. I have an Eco-Worthy 1000N to play around with.
Specs Include: 12vdc/3amps,
 

Thread Starter

sayerdesign

Joined Feb 17, 2021
8
Thanks for sharing that, Max.
I'm not sure quite the nomenclature you're using.
Is that three distinct relays, one switching the direction of the actuator on another pair working in conjunction to supply power through the cycle and then drop out?
Also, are those diodes bridging the external limit switches?
It's been 30 years since I've play with circuits, so please forgive my ignorance.
I appreciate the help!
 

MaxHeadRoom

Joined Jul 18, 2013
23,125
Thanks for sharing that, Max.
I'm not sure quite the nomenclature you're using.
Is that three distinct relays, one switching the direction of the actuator on another pair working in conjunction to supply power through the cycle and then drop out?
Also, are those diodes bridging the external limit switches?
It's been 30 years since I've play with circuits, so please forgive my ignorance.
I appreciate the help!
Looking at it again I see a slight mod needed. will re-post it
One relay 3 sets of contacts. Omron etc.
Yes diodes across the limits to make them uni-directional.
 

AnalogKid

Joined Aug 1, 2013
9,257
Post #6 has one 3PDT relay. The diode across the relay coil (lower right corner) is for transient suppression. The diode across the Reverse Limit switch (upper right) has to carry the full start-up and running current of the motor. Reference Designators - !

Two of the relay SPDT sections are wired as a standard, cross-connected, DC voltage reversing switch. Contacts with a slash through them are normally-closed. In the rest condition (motor not running, relay not activated), -VE is connected to RLS and the anode of the diode, and +VE is connected to the botton side of the motor.

The forward limit switch (FLS) is at the far end of the track / structure / whatever, and opens when the traveler gets out that far, so it sets the far-end movement limit. The reverse limit switch (RLS) is at the close-in starting point of the movement thingy.

At the start, when the switch is pressed, RLS is open because the mechanism is sitting on it, and FLS is closed so the relay actuates. This closes the contacts around the switch, which keeps the system running after the switch is released. Current to the motor goes through the diode around RLS until the mechanism moves far enough to let the switch close, bypassing the diode. When the mechanism reaches its far distance, FLS opens. This deactivates the relay, reversing current to the motor and opening the contacts around the start switch. The motor runs backwards until the mechanism hits the RLS. RLS opens, and the current direction cannot get through the diode, so everything stops.

ak
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
23,125
There is a bug in the one I posted, I will post an updated version, BTW what is the polarity of the motor leads
If you use one of the Omron or similar relays, they are 4 pole, so you just need one relay.
Max.
 

LesJones

Joined Jan 8, 2017
3,188
Hi Max, I agree with AK. There is no need for a forward limit switch as the NC contact forces it reverse by causing the relay to unlatch.

Les.
 

AnalogKid

Joined Aug 1, 2013
9,257
But the diode is wrong way around on the reverse LS. in #6
Again, don't think so. At the start, Rev LS is open because the actuator is sitting on it. The diode conducts only long enough for the actuator to move and Rev LS to close. Then Rev LS shorts out the diode while the motor runs both forwards and backwards. When the traveler returns at the end of a cycle, it opens the switch. The relay already is de-activaged, so the motor current path is through the NC normally-closed contacts. Now the diode is reverse-biased, and the motor stops. End of cycle.

Give it a rest; you got it right the first time.

ak
 
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