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Is it possible to bend a nitinol (Flexinol) wire using power that we get from an smart phone?

Discussion in 'General Electronics Chat' started by JJoll, Oct 1, 2015.

  1. JJoll

    Thread Starter Member

    May 7, 2013

    I was just wondering if it is possible to some how, design a circuit that can extract power from a smart phone such as iphone (potentially from audio jack) and actuate a nitinol wire? I am brainstorming ideas for a college project and I am considering a project in which I can connect a nitinol memory wire (around 94cm in length) to my smart phone and actuate it to some preprogrammed shape by touch of a button. I have been researching online and according to this website (table in the middle of the page) http://robotics.hobbizine.com/flexinol.html and my calculations, I would have to provide 3 volt, 320mA to a 94cm nitinol wire to actuate it but I probable can get 3V, 42mA out of an audio jack. My dilemma is that I can get only some minimal power out of iphone but nitinol wire is power hungary (specially in that length) I was just wondering if anyone have any suggestion about feasibility of this project?

    I have seen some circuits that can pulse a DC signal and deliver considerably higher current by using a cap or smaller additional battery.

  2. Roderick Young


    Feb 22, 2015
    The wire is going to be motivated by power, not current alone, so if you pulse high current with the same average power, it's not going to work, at least not unless the frequency is super low, and in that case, you'd be charging a battery or supercapacitor. The supercap might do what you need, but you'd have to charge it for a long time at your lower current from the phone battery, taking a substantial portion of the battery's energy.
    JJoll likes this.
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    There is not enough power available at the audio output of a smart phone to heat the wire, and certainly not enough to power Hungary.
    Last edited: Oct 2, 2015
    JJoll, Alec_t, absf and 1 other person like this.
  4. Sensacell


    Jun 19, 2012
    I doubt you could get 3V 42 mA from an audio output? With a diode bridge and a capacitor?

    Nitinol is super inefficient, small geared DC motors are far more efficient at converting electrical energy to mechanical.
    I have yet to see Nitinol used for much more that a few super specific niche applications, mostly its marketed as bait for hobbyists to waste their time...
    JJoll and KJ6EAD like this.
  5. sirch2

    Senior Member

    Jan 21, 2013
    As Sensacell says a small DC motor would probably be better. Could you not take power from the charging/USB port (don't know anything about iPhones) and if you really need to trigger it from the audio jack use a transistor to control the current?