Actuator control

I am a newbie and am attempting to build a control system to make a linear actuator move up/down in about 1/2 second intervals. So, up for 1/2 second down for 1/2 second and repeat this process until it is switched off. I want to do this as simply as possible. The actuator has no built in limiting and I am planning on using a 12v power supply. Any ideas? diagrams?

Do you want to go relays or electronics?? Do you have limit switches?

I would prefer to use electronics..but whatever is easiest. and no, i don't have limit switches, i don't really know what type to use either.

Do you need very accurate 1/2 second timing or just approximate?

What is the current and voltage rating of your actuator? Also will you be needing to stop the actuator for any other purpose other than switching it off?? Under my current idea, you need an actuator control that makes it rock to and fro the momet you switch it on till battery goes out right??

Just approx timing..but close to or less than 1/2 second..and yes, i need it to go back and forth more or less. it is an actuator from a power door lock system for a vehicle, so basic 12vdc ran actuator

Simplest way would be to use one of the 555 astable circuits (probably already one in the archives here) driving a power transistor that operates your actuator. Depending on the current draw of the actuator, then with it's 50% duty cycle you might need to heatsink whatever power transistor you use.

Using a MOSFET instead of a plain transistor will make it more power efficient if the currents are high.

You didnt specify your actuator's current requirement. I too will reccommend you a 555 astable for this simple application and for the driver part, it would have been better if you specified current consumption. However, a relay would be the best alternative for any quantity of current. Mosfets or transistors will require you to cause some problems when you wire them for the + and -ve cycles. It is possible but cheaper and simpler is a relay along with the 555.

ok, i will take a look at the 555 astable and repost when i get the actuators so i can give you more info on them. thanks for your help

another question though, i think the 555 astable will work perfectly except that i need the motor to go forward, then reverse...how do i get it to reverse? some sort of relay system to reverse polarity?

Tcg178 said:

another question though, i think the 555 astable will work perfectly except that i need the motor to go forward, then reverse...how do i get it to reverse? some sort of relay system to reverse polarity?

Click to expand...

You are going to need an H-bridge to provide the forward/reverse function.

hgmjr

Or use a DPDT relay wired as such.

If the current draw is low enough, there are a number of good H-bridge chips already out there to simplify your construction if you want solid-state.

So how would the 555 interface with the Dpdt relay? I understand how the 555 works but im kind of sketchy on the relay aspect. I know its asking a lot but could someone give me a diagram on how i would interface the 555 with the dpdt relay?

Just look in the circuit archives here; there are already examples. If you don't see those, or don't like them, there are also lots of examples in various tutorials around the web (probably also in the AAC ebooks).

EDIT: I think it's called the Albums section, rather than Archives.

Here you are with a 555 and a relay.
ON Time 521.41mS
OFF Time 503.11mS
Duty Cycle 50.89%
Frequency 0.98Hz

Guess the timings will do for you.