Hi there,

I am looking for some sort of push-pull component, where I can for example have three wires, 5v, 0v, and then a wire that if I send 5v down, it will push a cylinder fully, 2.5v - it will push a cylinder half way, and 0v it will have it retracted.

If you can imagine a car engine, this would be like the piston. I want to use it for making a kind of digger arm. I can think of a design using a servo but that wouldn't really be the traditional "hydraulic" way that an arm moves.

Do any of you know of a component like this? I have searched for solenoid components on ebay, maplin, all over the show, but to no luck.

Also, if I do use a servo, how strong are they?


Cheers,
Adam

 

Search "proportional control" and "linear actuator".

 

Perfect, exactly what I was looking for. They are pricey to buy but now I can see how they work, they seem pretty simple! Thanks a lot!

 

How about something like this:

http://www.mpja.com/email/08-23-11.asp?r=335052&s=18

With the encoder on the back of the motor, you could get pretty good positioning.

 

How about something like this:

http://www.mpja.com/email/08-23-11.asp?r=335052&s=18

With the encoder on the back of the motor, you could get pretty good positioning.

What does the encoder do?

 

http://en.wikipedia.org/wiki/Rotary_encoder

 

Well, the motor that Jaguarjoe linked to has a 50-slot photo tachometer on it; maybe you can just count the pulses from the tach to determine the extent once you'd retracted it to establish a zero point by hitting a switch or similar.

 

If you want it to behave like a pneumatic piston, then use a pneumatic piston with a proportional air valve.

By the way your pic looks exactly like a guy I used to work with. I actually thought you were him until I saw your location.