I'm trying to figure out if electric linear solenoids are the best option to activate an interface element on the touch screen of my smart phone.

I have also heard of linear actuators and pneumatics but wasn't sure if those are for different cases, even though they all operate in a similar fashion.

Also, does anyone know if there is a low power solenoid that exists? The lowest power consumption I saw is 5V-8V at 1 A but I'm looking for something that is really low power.


closed as primarily opinion-based by uint128_t, PeterJ, Bence Kaulics, placeholder, Asmyldof May 30 '16 at 8:10

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    \$\begingroup\$ Define "best option", otherwise no-one can help you. What is it that you want to do? Simulate a physical finger press, e.g. to test the durability of your screen, or do you just want to interact with the phone? \$\endgroup\$ – Marcus Müller May 28 '16 at 15:36
  • \$\begingroup\$ I just want to interact with my phone screen, thanks. \$\endgroup\$ – Rocketboy235 May 28 '16 at 17:11

A capacity touch screen really needs no force at all, so these kind of actuators are all horribly overpowered.

In fact, capacitive touchscreen actually do what their name says: measure the capacity between screen matrix and ground. When you put your finger on a screen, it forms a capacitor.

So you don't have to build a mechanical actuator at all. You just have to vary capacitance at the places you want.

I call this prototype that took me nearly 5 minutes to build A.W.E.S.O.M.E. (Advanced Wire-based Electrical Sensory Obfuscator Manufactured from Edibles). I made it from high-tech potato slices, and bits of wire.

ECG pads, which are cheap and can be bought in hundreds, together with ECG contact gel, which is cheap and can be bought in bottles, probably work just as well, but I had neither of these at hand. As little as I had access to conductive sticky tape or conductive glue that I wanted to put on my phone's screen.

So: here is A.W.E.S.O.M.E., with none of the V.I.C.E.s (Vegetable Interface Contact Entities) grounded:


and here with the croco clip connect to my heating pipe:


So, use short leads with no ground plane near, and a set of transistors with a high "off" resistance, and you should probably be able to build your touchscreen toucher without any mechanical actuator.

So, no, I personally don't believe that solenoid linear actuators are the most awesome way to interact with your phone screen.

  • \$\begingroup\$ Haha nice! That's actually a pretty clever idea. Anyway I originally was thinking about attaching some special material used in those cheap stylus pens used for tablets and smartphones on the solenoids. \$\endgroup\$ – Rocketboy235 May 28 '16 at 18:11
  • \$\begingroup\$ yeah, you could try conductive foam. There's actually small blocks of conductive rubber that are meant e.g. as contact between PCBs and LCD mounted atop of them, see for example majr.com/conductive-rubber-what-it-is-and-where-its-used \$\endgroup\$ – Marcus Müller May 28 '16 at 18:19

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