Design of a solenoid actuator

A need a very small solenoid to pull on a metal pin with a stroke of only about 1 or 2 mm. It's not hard to push the pin with my fingers, but I little harder to come up with something electronic I can use.

I pulled a solenoid out of a clock, which has a small soft steel core. The solenoid had lots of turns of very fine wire, but about 180ohm DC resistance, and I couldnt put enough current through to develop the pull force I need. So I rewound it with heavier wire (less turns though) but I was still getting nowhere!

So now I am trying a small DC motor which drives a gear (out of a mini RC helicopter). This might work, but the motor and gear assembly is a bit too big to fit where I need. Ideally, I would like something with a low profile, no bigger than about 10mm by 10mm, and about 25mm long, which can apply a force axially.

Anyone got any bright ideas what I could use? I think it would be a lot of trial-and-error to do a linear solenoid, so i probably need something geared that will fit in a very small space.

You may want to take a sharper look on a known working solenoid actuator. It's not just a coil with
ferromagnetic core. It's a magnetic circuit, that's usually closed, or at least reducing a gap when
actuated. The magnetic circuit is the secret of an effective solenoid actuator.

Of course you can also have a plain coil and a iron rod. But it's much weaker, because the flux isn't
concentrated in a magnetic circuit. In a graphic view, shortening the magnetic field lines (respectively
their path in the lower permeable material) causes the magnetic force.

To learn about achievable solenoid actuator properties, you can review some professional products, e.g.
**broken link removed**

You can also use magnetostatic field simulators to evaluate the behaviour of a particular actuator geometry,
e.g. Quickfield: www.quickfield.com
They have tutorials dealing with actuators, if I remember right.

junked old VCR machines are a great source for linear solenoids of the type your discussing.

I have also just been looking for a similar solenoid actuator, and you might find something suitable at
Solenoids, Door Solenoid, Electromagnets by Magnet Schultz e.g. MGBP010 rectangilar, 24 longX9X10mm, 2.5mm stroke, 24V, bistable, or even smaller GHUZ cylindrical, 8mm diaX 13mm long, 12V, stroke 1.5mm.

Prof78

It's a great portfolio of solenoids.