Syncing light blink speed to the RPM of a motor

Discussion in 'The Projects Forum' started by Raccaroo, Oct 17, 2015.

  1. Raccaroo

    Thread Starter New Member

    Oct 17, 2015
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    0
    Hello,

    I am designing a prop for a costume that requires some lighting I am not sure how to set up.

    I basically need to have EL wire connected to a motor that spins at a high speed, and I need to have the wire strobe at a high speed as well. I want this strobe speed for all wires to first be permanently synced to the RPM of the motor. Then after that is synced, I want to have a modifier that can fine tune each individual wire's strobe rate. This will allow me to achieve the stroboscopic effect AKA the wagonwheel effect, and have individual radial beams of light that rotate at different speeds and even different directions. I want them all to first be synced to the RPM of the motor so that no matter what speed the motor is at, the stroboscopic effect remains the same. I would even like to have the strobe be controllable as far as whether or not it is a strict on/off strobe or a gradual strobe, or possibly control the on/off ratio. But that last part is not absolutely necessary. Regardless, the RPMs will be quite fast. I'm not sure how fast, but obviously fast enough to create the effect.

    I don't even know the names of the devices used to control strobe speed and whatnot. I have a logical idea of how it'd go together, but not enough electrical knowledge to put together a prototype. I do know I'll need some kinda RPM sensor, a few poteniometers, resistors, and I think capacitors? Educate me! Also if anyone has experience with EL wire, how fast can it strobe? I've only ever set it up on a on/off switch.

    P.S. I did search for this, but it was kinda hard to know how to search for this idea since I didn't know how to word it.
     
    Last edited: Oct 17, 2015
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
    Never made one, but looks like there are several videos on youtube, looks like it uses AC around 150v @ 400 hz to 4khz, using a simple 555 timer oscillator...



    Heres one example.

    http://archive.makezine.com/21/primer/

    You're going to have to pulse the oscillator at the speed of wheel,with the strobe, so if your wheel is at 60 rpm, the strobe is at 1hz, faster rpm, faster strobe...
     
    Last edited: Oct 17, 2015
  3. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    If you want the EL wires to always sync to a ratio of motor speed, I'd use a PLL (Phase Locked Loop). Google Hall Effect sensors for motor speed detection.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    EL wire= new to me.
    One or more EL wires attached to motor shaft?
    Will need slip rings , one common and one for each wire.
    A motor with double ended shaft might be handy, one end for optical encoder disc or magnets, other for wires.
    One wire should give wagon wheel effect?
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    One issue you will have is brightness. The EL device will light up dimly at 60Hz and 120V AC - ie. just plugging it into the wall. But it will get brighter in proportion to the frequency all the way up to 2kHz or so. I'm not sure what happens at frequencies above that, but I don't think it gets brighter in a linear fashion. It does age faster at higher frequencies. If you want an EL to be the same brightness at 1kHz as it was at 500Hz, you'll have to drop the voltage.
     
  6. crutschow

    Expert

    Mar 14, 2008
    12,995
    3,229
    Syncing the strobe to the motor is fairly straight-forward.
    Having it synced at a slightly different frequency to get the wagon-wheel effect is more difficult.

    The easiest way may be to use a microprocessor to detect the motor speed and then calculate/generate a slightly different frequency from that for the strobe.

    An analog approach would be to convert the motor speed to voltage proportional to the speed and use that to control a voltage-to-frequency converter for the strobe.
    Getting the proper voltage-to-frequency gain and offset could be difficult however.
     
  7. camerart

    Active Member

    Feb 25, 2013
    517
    30
    Hi,

    My logic is to use a chip with clock, and a reflective shaft reader like this: http://www.radiolocman.com/shem/schematics.html?di=73221er clock between.

    Place a reflective mark on the shaft. Count the clock counts between each mark (one revolution) and so on, which changes at any speed. Flash your EL in time with the clock counts after the mark (number of clock counts = one shaft revolution) = stationary strobo, or less than the number of clock count for backwards strobo effect or more than the number of clock count for forwards strobo effect.

    Hope this helps. (and makes sense)

    Camerart.
     
    Last edited: Oct 18, 2015
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