Controlling a DC motor from an Audio Input (need help for deaf brother 1

[EricEllis]

Hello,
I am trying to control a 1.5V - 6V DC motor from an audio source. I would like the motor to vibrate harder if the noise is louder, softer if it is quieter and not at all if there is no sound. My brother is deaf and he likes to turn the volume up on his computer so he can feel the sound. As you can imagine, my parents get really annoyed at him for making so much noise. So I thought I would build him something to give him the feeling but not make so much noise.

Does anyone know how I can control the 1.5 - 6V DC motor from an audio source? The audio source would most likely be the audio out of a computer's sound card. I know that there is a backpack that you can buy that does this sort of thing, but that isn't what doesn't really fit this situation. I also plan on building it twice so he can have a stereo sensation. PLEASE if you know how to do this, please let me know! I would like to give this to him for x-mas.

Thank you for your help!

Eric

 

[OperaHouse]

Time is running out for Christmas. A simple way is to run the low level audio into an op amp to boost it to several volts. Rectify this with a diode and feed it into a darlington power transistor with the motor connected to the emiter. The motor would have an offset weight. The trouble is the response time of speeding up the motor. I think a better solution would be a switching regulator IC (like a TL494) that operates at a constant frequency (maybe 100HZ) driving a modified solenoid or other electromechanical driver. The PWM IC would then increase the strength, but frequency would still be the same. If you go to the car audio shops for the real wackos, they have low frequency drivers that get mounted to seats and the floors to drive your butt at low frequency. These are as low as $25 a pair and only work up to about 300HZ.

 

[EricEllis]

OperaHouse, thank you for the ideas. I was thinking that way before. I need to figure out how much amplification I'll need to drive the motor. I would prefer to stay with the motor idea, instead of the seat mounted kickers, because I'd like to keep this semi-portable. Also, since I was part of the many layoffs that have been happening, I'd prefer to keep this on the less expensive side. It was just an idea that I thought would be nice for him. Keeping this usnit small will allow him to stap it onto his arms (one for each) so he can tell what side the sound is coming from. I think he'd like that part, especially in games!

Thanks again for your help and if anyone else has ideas or schematics that would fit the general idea, please let me know!

Thanks again,

Eric

 

[automatic2]

xmas is coming too fast, but here's an idea that you might want to consider. Look into to miniature pizos and rig them up so that they will contact the back of the neck, just below the skull. One each side for stereo. The effect will come from direct contact. Ordinary head sets keep the speaker at a distance to the ear, but you'll want to modify them for skin contact. You have a perfect experimental situation where some simple modifications could lead to a marketable product. Your brother can enjoy sensational feedback and you won't have to worry about layoffs.

 

[OperaHouse]

I'm thinking a simple adjustable op amp amplifier with a gain of about 70 would do. That would work down to about 0.1V of some audio outputs. Headphone jacks are probably about a volt and need much less. Feed the output of the amp through a 10uf cap to the center of two stacked diodes in series. - to the minus supply and + to the base of a NPN darlington transistor (or to transistors connected that way. Filter this with about a .1uf capacitor. The op amp should be able to supply about .005A and with a darlington gain of only 100, this will easily supply up to about 0.5A to the motor.

On the switching regulator design, I failed to mention that this is the type with two outputs for push pull design. If you use only one output, you get an on duty cycle from about 5 to 45%.