Linear Accuator


Thread Starter


I'm aware this is a serious forum, and I'm worried my article may be of low value but here goes.

I'm trying to make a small device to press a single keyboad key or mouse key repeatadly for a school project. I was hoping you experts would know where I could purchase a small, afforadable motor that produces linear motion or even a toy / device that has such a motor that I could recycle. Something in the range of 40-120 retractions per minute. That could even go for a few hours and strong enough to depress a keyboard
or mouse key.
Use a motor with a cam on it. Either press the button directly or have the cam push a pushrod (i.e. a cars valve train). Quit thinking so high tech when you don't have to.

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I just happen to have some solenoids that were used for exactly that purpose. I would be happy to give you one for your project. Contact me
off list if you would like.
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Motorized toys typically have slow rotary geared motors, not what you're looking for. Even if high speed, you would need to convert rotary to linear
motion. What you are describing is a reciprocating linear motion displacement of a quarter inch or so at about 1 Hz (one cycle per second). The force is very low and the average speed is one stroke cycle (1/4 inch x
2) in one second, or 1/2 inch per second. A very low power/size device.

A linear "voice coil" motor actuator may be what you need. Not an everyday device for sure. My information shows these tiny devices are for short stroke and high frequency. I did find one manufacturer that may be able to
help you:

BEI Sensors & Systems

Kimco Magnetics Division



Good Luck.
Use a motor with a cam on it. Either press the button directly or have the cam push a pushrod (i.e. a cars valve train). Quit thinking so
high tech when you don't have to.

[email protected]
Why don't you consider a solenoid. Dormeyer makes a wide variety. Perhaps you can salvage one from an old washing machine.

Consider a short on time, like 20%, do not leave on for a long time, and allow the solenoid to do a full stroke.

Bruce Durdle

What about a relay? one of the old Post Office 2000 ohm type with judiciously installed levers will do. Bruce.
Are you sure you even need a linear actuator?
You can press buttons with something stuck on the axle of a plain old DC motor. Is this just to repeatedly test a button?

There are also other ways to convert rotary motion to linear.

I'd steer you to some hobby/robotics groups:

Hi again,

I looked up everything you all suggested. The valve train idea seems cool, but just alot of parts to make one.. and how would I power it .. I'd need gasoline to make a combustion.
The motor with something soldered to the axel would be cool too.. but how would it return to it's starting position? I guess maybe like an oscilating fan mator.. but fans oscillate slowly.. maybe I could find a small fast oscillater. The one I like the best is the solonoid idea with a relay switch. Those
solonoids rock! I found some online for as cheap as 1.79$ and small relay switch that blinks as fast as every second for 8$. I'd just need a solonoid that has a heavy rod and mount it where gravity did the key pressing. The robotic sites were awesome too. I was thinking of making a mount from a flower pot wire harness but those hobby sites tuned me on the Lego pieces. With all
the different sizes I could make a very precise mount.. height wise. I could borrow my dad's drill and make some holes to mount my machine gun motor or a solonoid. Yah!
Well, thanks again.. sorry if I'm rambling you got me all excited :).

Thanks everybody, Rich, John, Rufus , Tom, Bruce and Bob :)

I read Rich's advice first .. to keep it simple. So I ordered a battery opperated automatic toy paintball gun ($15). I guess I took the easy way out, sorry if I let you all down. I was kinda worried that what I needed was small and that any manufacturer of such devices would be so professional that they may have like a minimum purchase requirement. Anyways I figure I could take the flint hammer mechnism part out and mount it somehow over the keyboard/mouse. I'm concerned it may be too high impact and vibrate alot so I'm going to tape some air-bubble packing material on the end of the hammer. I'm also worried it may be too fast so I plan to try using a dimmer switch to regulate the battery power to a slower speed .. hopefully slow it down and reduce impact further.

Thanks again..I really appreciate the time you took to answer me :). I will look into your suggestions further if my plan doesn't work.


Johan Bengtsson

Hmmm, a dimmer? Like the ones you have in the wall to control the amount of light in a room? The ones only working with AC? They won't do any good on a battery feeded system like this
(DC) if you don't do a lot of extra stuf, and that would be easier to do without the dimmer anyway....

But lego would be an option, there is a nice small DC motor availiable and making that one do some linear moton once per turn would be very easy really....

/Johan Bengtsson

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Try going to "": for some small SMA linear motors that use SMA "smart material" "electric muscle". They are very small and really rubust and inexpensive. I know that there are not many people in Motion control that know much about SMA technology, but my company works with SMA for very powerful actuators using SMA (i.e. 17,000 lbf. w/ size of paper towel tube & one moving part), so I know the SMA actuators work well. Nanomuscle specializes in the small motors you are seeking. Not sure if above site has supply line compleatly done yet, but they have just commenced some contracts with major toy companies like Hasbro and Jetta. Might want to check it out.