I am looking for a tiny push-type solenoid that can be driven with milliwatts. The plunger need only move 2-3 mm. Does such a thing exist?

  • 2
    \$\begingroup\$ When you say 'driven by milliwatts', do you mean that the peak power must be milliwatts, average power while it's operating must be milliwatts, or average power overall must be milliwatts? Or just a generic term for "I'm running this off of a puny battery"? \$\endgroup\$
    – TLW
    Oct 19, 2017 at 2:42
  • \$\begingroup\$ It really just means that it should run on a tiny battery. I should also have added that it should only be activated for a few seconds at a time, with hours of rest in between. \$\endgroup\$
    – augustzf
    Oct 19, 2017 at 7:43

1 Answer 1


It depends how much force you need. In general, you need quite a bit of current to run even a really tiny solenoid (hundreds of milliamps), and you need to hold that current to keep the solenoid pulled in or pushed out (depending on configuration). The force is proportional to the magnetic field, which is a product of the number of turns and current through the coil - so, you are usually looking at a fair bit of power to operate a solenoid. You could quite easily simulate this in FEMM if you're familiar with using that software.

There are other options for really small linear actuators than solenoids though. Many cameras use really really tiny stepper motors for adjusting lens focus. See this post for more details. I have seen these types of steppers available with leadscrews on AliExpress before. They will need high amounts of current to step, however, you only need to supply that in short bursts when actually stepping - so, you could charge up a big tantalum cap and dump it into the stepper windings at each step, and your average power consumption could still be down in the milliwatts. It wouldn't be fast, but if you're power-limited (such as from running off a coin cell battery or something) it should work.

Finally, there are electropermanent magnet actuators, which can be used as very low-power, very small bistable solenoids and stepper motors. An electropermanent magnet exploits the fact that AlNiCo permanent magnets are pretty easy to demagnetize, and NdFeB permanent magnets are very hard to demagnetize. The AlNiCo magnet is put into a magnetic circuit in series with the NdFeB magnet and ferrous keepers. Flipping the field direction of the AlNiCo magnet with a coil causes the field from the NdFeB magnet to be either confined to the circuit or forced to travel in the air, creating a "switchable" permanent magnet.

These are very cool when used as tiny actuators, but they aren't commonly available commercially, so you would have to build your own. Ara Knanian's PhD thesis is the best resource I've found for the theory and construction of these devices.

  • 1
    \$\begingroup\$ Great answer, thanks! I may need to look into using tiny steppers instead. Force is not a real issue here, only (linear) motion. \$\endgroup\$
    – augustzf
    Oct 18, 2017 at 17:32
  • 1
    \$\begingroup\$ @augustzf: sounds good! I've updated my answer slightly to expand on what the electropermanent magnet does, but I think a stepper is probably the best bet for something that you can buy off the shelf. \$\endgroup\$ Oct 18, 2017 at 17:34
  • 3
    \$\begingroup\$ Also, you can provide a bistable mechanical linkage, which will maintain one position or the other without power. This is how automatic urinals work, which get up to 10 years life out of 4 AA cells. \$\endgroup\$ Oct 18, 2017 at 19:03
  • \$\begingroup\$ If one can reduce friction and stiction in the system then one can reduce power needed also. In practice this is difficult. \$\endgroup\$
    – joojaa
    Oct 19, 2017 at 6:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.