hi i am looking for some help with a project i am making, i need to make a linear actuator go forward 10mm then stop wait for 3 seconds then return and stop then i need to press a button to make that cycle again, but i have no idea how to do this, i have got limit switches and timer relays which I'm hoping thats all i would need.
Anyone know how i can do this, I would be great full for any assistance as this is driving me up the wall.
cheers David
Need more information. What kind of actuator? How do you control it? Are you using any kind of controller or is this all relay logic? What kind of components are you using?
What voltages are involved? And are all the components rated for the same voltages?
This circuit is a very off-the-cuff sketch of how such a circuit might work. Each relay holds itself on until the limit switch is tripped. As drawn, the Retract relay triggers instantly when the Extended Limit switch is tripped, but if that relay had a delay timer, it should work as desired.
When the Retracted limit switch is tripped, both relays end up de-energized, leaving the circuit idle until the Extend button is pushed.
When both relays are open, the NC connections of both relays connect both sides of the motor to ground. If both relays were closed together, both sides of the motor would be connected to VCC (5V in this example). With the only one relay energized, the motor will rotate. Which relay is energized will determine the direction of the motor's rotation.
One drawback: as drawn, if neither limit switch is closed, it's not possible to energize either relay. Wiring the common of the Extend button to Vcc instead of the NC contact of the Retracted limit switch could resolve that.
linear actuator is any actuator that can move on a straight line.
in fact this part of info is not even relevant... it could have been rotary actuator that turns back and forth by some angle.
the real question here is how to control it and there is no mention of interface. could be hydraulic, pneumatic, electric or something entirely different. some electric actuators move simply by powering the motor directly. some require fieldbus to work. some are manually operated (like hospital beds etc.). direct drive actuators could have different types of motor (AC or DC or stepper or anything else). some may have a lock or holding brake though many may rely on gear ratio to prevent back driving. so there is tons of possibilities and you provided no details about your specific case.
the simple solution to make this work is to create some sort of state machine or sequencer. simplest sequencer is mechanical drum (like music box) driven by spring or slow turning gear motor that activates some switches using cams.
another way is to use smart relay (mini version of a PLC) and do things in software. another option is to hardwire it using relays and timer/counter etc. but troubleshooting will be harder.
all replies asked the same things - what kind of actuator this is - in terms of interface/control, not type of motion but you still have not answered.
assuming it is the simplest case where actuator runs forward or reverse when jogged manually, simple ladder diagram like this would do, either hardwired or in some sort of controller (smart relay or PLC):
for clarity,
prefix X is for inputs (like start button, forward and reverse limit switch)
prefix Y is for outputs (run forward, run reverse). this will drive actuator.
prefix B is for internal tracking bits
timer is TON type
if this is implemented as hardwired circuit, Y and B are relays. also i posted it to be as readable as possible but for hardwired version this could be simplified a bit for less wiring.
