Linear actuator uses a lead screw driven by a permanent magnet dc motor to create linear motion from a dc voltage. When power is removed linear actuator will hold its position. However, if a force large enough to overcome the internal friction is applied, the actuator will back drive. Here is an ultra-simple circuit to connect your linear actuator to a voltage source and be able to control the direction manually using a “digital”- push-button switch. Simply push the button-switch once to extend and once again to retract the linear actuator. You can position the switch at the required distance from the actuator using additional twin-cable.
The circuit is suitable for use with dc supply voltage of 12 volt, and is built around a CD4017 IC to toggle an electromagnetic relay with dpdt switch contacts. Partial view of the author’s prototype is shown here. The prototype was tested with a 2-wire mini-linear actuator (with built-in limit switches, but without a built-in potentiometer), borrowed from my neighbour (who is a mechanical engineer). The DPDT relay used is an O/E/N pcb relay with part number 58-12-2C (285-Ohm Coil Resistance).
Here is the full-schematic diagram of the linear actuator controller:
The bi-color LED (LED1) in the circuit is used to indicate the direction status, ie Red for UP and Green for DOWN. Components C3 and R2 forms a power-on-reset circuit. Diode D2 is required to toggle IC1 (CD 4017) outputs as per the pushbutton switch (S1) activity. Components R3-C2-R1 helps S1 to generate a valid clock signal for the IC1 clock input (pin 14).
If you are searching for linear actuators, have a look at: http://www.linak.com/products/linearactuators.aspx
It’s with regret
I always want to take clear photos that really show off my prototypes, including wide shots that capture the entire set-up, and close ups of important sections. Unfortunately, I don’t have a good digital camera to make the snaps clear and vibrant!