# Energy conversion from Electrical to Mechanical

I have a requirement where I have to design a very small device capable of pulling in and out a small piston through a feedback.
I know it can be done using motor but AFAIK I need higher voltage and current which is not possible through, in my case,a button cell rated 1.5 V.

Here I seek your suggestion, is there any other effective solution to convert electrical energy to mechanical energy.I thought about an electric spark to initiate some chemical reaction(like in automobile) but it was complete failure as I needed to generate high voltage.

• How much force, over what distance, at what speed and how often? And how long do you want the battery to last? – Dave Tweed Sep 14 '12 at 21:33
• @DaveTweed:- I have to drag a 20-50 gram small iron cylinder by 4-7 mm. – perilbrain Sep 14 '12 at 21:40

Look at piezo linear actuators. They work at relatively low energy rate, slow speed, low torgue, accurate movement in range of few mm. With correct driver the motor will consume very low power

Solenoid - might eat the battery but with a hand built unit and the rare earth magnets available, it should be doable.

You don't mention amount of force of the amount of mass that needs to be moved.

• I think at 1.5v, your idea will go into trash :) – perilbrain Sep 14 '12 at 21:41
• Why? a solenoid is a current device not a voltage device. A fine wire with multiple turns will work fine. – placeholder Sep 14 '12 at 21:47
• So it means a logic of solenoid valve? great thanks,I'll give it a try.... – perilbrain Sep 14 '12 at 21:48

Some small motors can indeed run on 1.5 volts and low current, they just have correspondingly low output power. You simply cannot do more work with a battery than the total energy contained in the battery, regardless of the device you use to perform that work (motor, solenoid, or otherwise).

mechanical work (joules) = piston force (newtons) * piston travel distance (meters) * number of cycles

energy in coin cell (joules) ~= cell voltage (volts) * cell capacity (ampere-seconds)

In the case of using the electricity to spark a combustion reaction, then you're using the energy of the reaction to move the piston. The energy still had to come from the chemical fuel, so why not just use the space for fuel/combustion chamber/valves to fit a larger battery instead? Even a AAA battery has much more energy than a button cell.

• This system is more complicated,I can have a combustion(exothermic) mechanism in very small space but compromising with size and weight is difficult.(Some institutional research related to biology :( ) – perilbrain Sep 14 '12 at 21:58