Re: Fw: Speedometer cable

["Steve Rubano" <srubano@xxxx>]

If you seriously wanted to do this, I would not recommend using an 
infrared led and pickup to count the pulses. If any dirt or dust gets 
onto the optic of either the sending LED or receiving, it will stop 
working. Since it's in/near the wheel, there is ALOT of brake dust 
that accumulates there that can easily get onto the optics. I would 
suggest using a magnetic sensor (similar to the ones used for anti-
lock brake sensors) to count the pulses. You would have to make a 
collar that would have splines on it. As the collar would turn, the 
splines on the collar will rotate passed the magnetic sensor, it will 
generate the required pulses. You could probably get away with going 
to a junk yard, getting the splined collar and magnetic sensor off of 
a car with antilock brakes, and engineer a circuit around that.

IMHO I don't think it would even be worth it since the cost of 
building this along with a digital dash would far exceed the cost of 
a replacement speedo cable. But then again if you wanted to be 
different then I would go with the magnetic sensor.


>snip< 

> What I wanted to accomplish was to eliminate the angle-drive and 
come
> directly off of the center hub with a 'squirrel cage' optical 
cylinder.
> Shine an infra-red LED & pickup through the cylinder and count the 
pulses.
> I originally got this idea as a replacement fix for broken angle-
drives.
> The guts of the speedometer gauge would be replaced with a 
galvanometer and
> then work like many modern cars. From the outside, everything 
would look
> original and also be maintenance free.

>snip<