Operating 4x Syringes (hydraulics) OR an easier way?

Hi All,

For a bit of background: I’m in the process of building a hydraulic powered arm (see http://www.instructables.com/id/CARDBOARD-Robotic-Hydraulic-Arm/).

My first thought was to replace the entire hydraulic setup with 4x mounted linear actuators but have quickly come to realise that this is a very expensive option for the length of stroke that I’m after.

My second thought was to build some kind of stepper motor, track and rail rig to manipulate the control syringes but this seems too elaborate for my beginner build skills.

Is there a better way to do this? Are there cheaper/simpler options that I could look at?


You could probably use servos directly to replace the actuating syringes. Or, perhaps you could keep the syringes and use servos to operate the pump syringes.

Another cheap but, slightly more complicated, solution may be to use low-geared DC motors to turn screwed rods to cause the linear motion. But that will need motor drivers and limit switches as well as the mechanics for screw mechanism.


Thanks for the reply. When you say replacing the syringes with servos directly, do you mean servos that extend outwards or servos that rotate (I'm not sure if I'm getting my terminology right)?

How would you recommend setting up the servos to drive the control syringes?

Cheers for your time! Much appreciated.

I was just thinking of regular servos that rotate. Attach a stiff wire to the servo arm, or some wire-in-tube like the model flying guys use.

Use a longer arm if you need more motion.

Or maybe just attach the servos directly at the hinge points - but that puts weight on the arm which may not be desirable.


Cheers Robin.

Should I be looking specifically at digital servos? Do you recommend any specific models?

Also, how should I go about powering the four servos?


I have no recommendation. You need to choose servos with sufficient torque to move your project without overloading the servos.

Servos with ball bearings and metal gears will last longer - but may be overkill if your project is only intended for a short demonstration.

Digital servos appear the same to the Arduino but have more sophisticated internal electronics. If they are only a little more expensive they may be worth it. A great many model airplanes were flown successfully before digital servos appeared on the scene.

You need a suitable power supply for the servos - a pack of 4 x AA cells should get you started. Don't draw motor power from the Arduino 5v pin. And make sure the servo GND is connected to the Arduino GND.


Perfect, thanks! I'll be back some day soon with a finished project.