I could use a little help. I have a 12DC, 4" stroke linear actuator. Can I continuously cycle the actuator? If so how?

Thanks,

chdlaser

 

If it reverses direction with a polarity reversal in the power supply, you can design a circuit to swap the polarity at the end of each push stroke, and at the end of each pull stroke. You can do that with limit switches, or perhaps by timing. Is that what you mean?

 

Is the actualor rated for continuous operation?

How is it controlled?

We are not mind readers.

 

Tracecom - Yes I was looking for a polarity reversal, my thoughts were to use limit switches to control the stoke length. Not sure what limit switches will work for this application. I'll try to attach a pic of my device. I really appreciate your help!!

 

Generally, limit switches are selected based on the mechanical parameters of the device; lever operated microswitches are often used. Post a link to the specifications for the actuator.

 

Is the actualor rated for continuous operation?.

They usually aren't.

 

Generally that's true for a lot of apps, as people use these for some high load applications (like lifting things). But it can run continuously if the load is light enough that the DC motor runs at a temperature that can be tolerated.

It's really just a DC motor and gearbox, so like any motor+gearbox it can run continuously as long as load and speed are under the critical values.

 

you are correct. I should have specified "they usually aren't rated for continuous operation at rated load."

 

My question to the OP still stands. Is the actuator he want to run continuously rated for continuous operation (at the load he is going to be subjecting it to)?

 

Does acturtor have built in limit switches? If so monitor motor current via low value sense resistor; every time current falls, trigger a toggle flip-flop which then controles either a relay or H Bridge.

 

Another fly in the ointment; cycling causes much more power dissipation in the coil than continuous use does because you have the constant starting current.

 

Yet another fly.
Running continuously and immediately switching the motor direction is harder on the motor and gearbox than intermittent operation. It would be good, at the very least, to have a short pause between direction changes, or if possible to detect near the end of travel and provide some deceleration and acceleration.

 

Another fly in the ointment; cycling causes much more power dissipation in the coil than continuous use does because you have the constant starting current.

I disagree...
The constant current runs when you have a continuous current (DC) through a coil and only the resistance of the wire in the coil will be seen as the load.

When power is applied and the magnetic field is forming, the inductive reactance slows current flow through the coil - until the magnetic field stabilizes. Repeatedly disconnecting the coil without a diode to avoid inductive kickback may cause heating. I doubt the start-up will be a big effect unless the load is so large that the actuator movement is impeded

 

^- You're forgetting that when a motor starts up, work is being done to accelerate the rotor mass and coupled load up to speed. That work is supplied by field current. It's not exactly like a simple coil.