Audio Jack to control remote control car

[dmnyanks]

Hi,
I'm wanting to make a simple remote (wired) control car controlled from my laptop.
It seems like the only controllable output my laptop has is the headphone jack (the usb would obviously require some sort of micro controller)


The idea is to use 'square waves' to control two motors (left and right channels) allowing me to control the car from an audio file.

So this leads to several questions:
1. Can I actually a constant current output?
2. Would I get enough gain from a midrange audio amplifier to power a (very small) motor?
3. What other problems am I likely to face?

Cheers

 

[crutschow]

The motor responds to the average (dc) value of a high frequency square-wave signal applied to it. The problem with your scheme is that the audio output would be a square wave with equal plus and minus peaks (average value is zero). The motor needs square waves with one side of the wave at zero volts so the average is not zero.

That's not readily done with audio amplifiers since they generally have capacitor coupling in their circuits which forces the average voltage output to be zero. (Necessary for speakers since you don't want any dc flowing through them).

You might be able to drive the motors with a simple transistor switch that is driven by the audio signal. The first step would be to measure the output voltage from you laptop to see how much gain you need to drive the switch.