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I am looking to make a pencil whose tip moves to create a waveform as you move it across the paper.In essence, I want to be able to record a sound and then play the sound through the pencil whilst I draw with it, of course, I will use software to lower the frequency to make it more of a waveform and not just a vibration.

I have many ideas but I am thinking of using a solenoid to actuate a pencil which I can move across some paper. Sadly, I do not have access to one to experiment with so I was hoping someone could hook a small solenoid up to an amp and tell me the results before I buy one?

If not this, what is the best way (using an amp) that I could achieve the desired effect? I have considered using a subwoofer but this will be bulky.

I want to keep it simple which is why I am not considering the use of a servo.

Thank you

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  • \$\begingroup\$ What frequency range are you expecting this to work for? \$\endgroup\$
    – HandyHowie
    Commented Oct 3, 2017 at 13:59
  • \$\begingroup\$ 1-10Hz would be best for drawing I guess. \$\endgroup\$
    – Abdel Darwish
    Commented Oct 3, 2017 at 14:02
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    \$\begingroup\$ Sounds like you want an old fashioned pen plotter of the type that used to be called a chart recorder. Used in ECGs, seismograms, and B&K audio test equipment. \$\endgroup\$
    – user16324
    Commented Oct 3, 2017 at 14:05
  • \$\begingroup\$ Last time this was done the guy used a needle instead of a pencil and draws grooves on instead of drawings. I believe there was a reason for that. \$\endgroup\$
    – user3528438
    Commented Oct 3, 2017 at 14:07
  • \$\begingroup\$ Yes, a portable pen plotter of sorts. And all I want the pen/pencil to do is wobble from side to side to a given audio input. \$\endgroup\$
    – Abdel Darwish
    Commented Oct 3, 2017 at 14:09

2 Answers 2

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People used to routinely hook pens up to galvanometers to draw lines on paper. The paper moved with constant velocity. These devices were called chart recorders.

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If I were going to attempt such a thing, I would probably start with a small DC vibrator motor — the kind used in cellphones, etc. When fed with AC, the weight won't spin around; instead, it will just jiggle back and forth — i.e., a kind of rotary solenoid.

Mount it to the upper end (eraser end) of the pencil, grasp the pencil lightly in the center, and draw the tip lightly across some paper. You should get some recognizable waves.

Optimizations:

  • Try different orientations of the motor body to get the best sensitivity.
  • A piece of spring wire (e.g., piano wire or guitar string) can be used to keep the weight centered in the neutral position.

Such motors are dirt cheap on the web, so no, I'm not going to try it for you.

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