Changing resistor value when wheel speed change.

[piccolo]

This is my first Thread, so let’s hope I’m in the right section.

I want to integrate my indoor bicycle with my gaming Pc. I want to control the speed of the game using the speed of the pedaling motion.
I can control the speed thru the joystick port using a 10k pod. Now I want to go one step further and connect that “pod” to the wheel of the bicycle.

I have a magnetic pickup on the wheel, what can I use that will use the trigger frequency of the pickup to change the resistance value of the pod.

I really hope this makes sense

 

[wannaBinventor]

You could use a uC with it, and then run the pickup frequency through a LU table/array to convert to a digital signal that needs to be sent to a digital potentiometer than can adjust the resistance.

 

[piccolo]

Wow, thanks but you went over my head.
do you have an example?

Im a Mechanical Engineer, playing with the electronics. I have lots to learn.

 

[magnatro]

it's a "pot" not a pod pot == potentiometer
well, you are a mechanical engineer right? cant you device something that converts rotations to linear motion? in my mind there is something:

it may not be a solution, but its better suited for you (i think)

 

[wannaBinventor]

I don't have ME experience (will, I don't have any EE experience either, ha), but I can maybe give you some more details on what I'm talking about.

I think what magnatro is talking about may be possible, but from an engineering perspective I think it kind of silly to design a large system that could be replaced by a a few millimeters of silicon.

The way this works is as follows:

On a PIC, you use the CCP (capture, compare, pwm) module to count the pulses. You could use multiple pickups at at 180 degrees to double the resolution, or at 90 degrees to each other to quadrouple the resolution (etc, etc). You run these measurements through a lookup table, for example, in your program that tells the PIC to set the digital potentiometer to a certain resistance. It sets this by setting or clearing certain ports, or perhaps by UART, depending on the digital pot's interface. Just see if you can find a tutorial on the CCP module and digital pots and I think you will get what I'm saying.

 

[Diver300]

If you use a friction device it won't work. The friction force does not go up smoothly with speed. Mechanical speedometers use magnetic induction, but they rely on the needle having little friction.

If you fit a generator to the bike wheel, and don't have any other load on the generator, the voltage from the generator should be proportional to speed.

You will probably need to rectify the AC from the generator to DC, and smooth it with a capacitor.

The joystick is probably wired as a potentiometer,(Potentiometer - Wikipedia, the free encyclopedia) not as a variable resistance. If so, the electronics are looking for a variable voltage.

With a bit of luck and a fixed voltage divider, you might be able to couple the smoothed output of the generator directly to the controller electronics.