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I'm looking for a certain component - not a concrete shopping recommendation, but rather if this kind of device exists and what it is called.

I need a little actuator that has the following properties:

  • linear motion (travel ~1 cm)
  • no intermediate steps required (just goes full to the left or to the right)
  • fast switching
  • no high force neccessary (should just be able to flip a mechanical switch)
  • small package size (say 3x3x1.5 cm)

What I'm looking for is basically this:

                                enter image description here

I put on a voltage, and the rod bumps out to the left. Reverse the voltage and it bumps to the right. The rod should be protected from fall out by a tab, but there need not be a spring to force it back to the middle. It can remain where it is when there is no current.

If I hold the current for a few seconds, it would be great if it would remain excerting a force, but it would be also ok if the force would be cut - it should just not melt.

I've found solenoid actors, but they are mostly just push or pull type, with a spring, and also they are too bulky:

                                                enter image description here

What I'm also not looking for is the kind of linear actuator where you have a rotating motor, and that pushes a screw out or in. I really just need a "bang a little rod to the left or right" solenoid in a box. Any idea where I can find this (or a suitable replacement)?

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    \$\begingroup\$ Looks like a solenoid to me.... \$\endgroup\$ – DerStrom8 Jan 30 '17 at 11:58
  • \$\begingroup\$ Model train points/slip actuator? \$\endgroup\$ – Andy aka Jan 30 '17 at 12:01
  • \$\begingroup\$ How about 2 coils placed end-to-end sharing the same plunger? Energize one coil at a time. \$\endgroup\$ – Tut Jan 30 '17 at 12:17
  • \$\begingroup\$ @DerStrom8 Sure it's a solenoid! But I'd rather not just solder two wires to a coil and put a bolt inside (mechanical tolerances, durability, potential for short-circuit and burning down the building). You can get ready-built solenoid actuators (people seem to colloquially call the whole actuator "solenoid", not just the coil?!), but every one I've found has a setback spring and goes only in one direction (push or pull). \$\endgroup\$ – jdm Jan 30 '17 at 12:36
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    \$\begingroup\$ Two coils so you don't need a magnet for a plunger. \$\endgroup\$ – Tut Jan 30 '17 at 13:30
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So, at least I found out that what I am looking for exists. It is called a reversible (or double-action) solenoid actor *. Here is a link to an example product listing.

Unfortunately, all reversible solenoid actors I found on the market are rather big, and my idea behind using one was that I wanted something with a small form factor (smaller than e.g. a step motor or rotational actuator). It seems, if I ever get around to building my project, I would just place a magnet on the thing I want to push, and place a reversible electromagnet at some distance.


* I actually found it via the German term, Umkehrhubmagnet (in case it helps anybody).

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Your loose specifications allow this (a D'Arsonval meter movement):
D'Arsonval meter movement Many of these meter movements spring-load a pointer offset to the left. A few have centre-pointers, or allow mechanical adjustment of pointer position. These movements are very sensitive to coil current - some swing full-scale with 50 uA. Iron vane movements are similar.

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  • \$\begingroup\$ Hah, that's actually pretty interesting (that's why I also asked for alternative ideas)! I fear it's not going to work well, since I'd like to be able to manipulate a mechanical switch. While it doesn't need much force, the meters I remember from school were quite flimsey, and I'd worry that I'd wear out the spring in the middle if the needle pushed against the switch with to much force. Also, I haven't seen one of those as an orderable component (admittedly, neither have I seen a dual-action springless linear solenoid servo :-)). \$\endgroup\$ – jdm Jan 30 '17 at 22:49
  • \$\begingroup\$ @jdm Well, I've seen such a movement (made by Ganz, Hungary) that has enough force to trip a mechanical switch cut-out that performs an equivalent function of a fuse used in other meters. Its meter movement has 30 uA full-scale sensitivity. Far too expensive for your app, but it can be done. Have used cheap D'Arsonval movements to drop a "flag" to block an optical photo-coupler of the Infrared LED-to-phototransistor type. \$\endgroup\$ – glen_geek Jan 31 '17 at 0:49
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Couple of ideas for you to consider.

1) Wind a solenoid coil around a center hollow cylinder large enough to slide a rod-shaped neodymium magnet through. The magnet makes the solenoid polarity sensitive. A little bit of playing around should show you the best position for the magnet to rest in both of the desired positions.

2) Wind a dual-coil solenoid, where the coils are placed end-for-end right next to each other. The core can be mild steel but a neodymium magnet may have greater force.

The idea is that you would activate one coil or the other, which will move the core between the two positions.

Your solenoid coils will require several thousand turns of thin-gauge magnet wire.

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