Using Hall Sensor As Bike Computer Sensor

[cohberg]

My bike computer's reed switch/sensor is pretty sketchy at best. (Tends to stick closed randomly stay open in close proximity to good neodymium magnets)

Has anyone used a hall sensor as a replacement for the reed switch/sensor?

 

[mvly]

I have done it on my autonomous rc car using the sensor on the motor. So I know it can be done. All yiu would need to do is biuld seperate micro controller to pick off the sensor wire and translate that into distance which then can be translated into speed.

 

[cohberg]

But could I just rewire the bike computer harness and replace the reed switch with the hall sensor output from the rear hub?

 

[Tiverion]

My bike computer's magnetic sensor is pretty sketchy at best.

Could I use one of the hall sensors as a replacement for the magnetic sensor?

If you can't get a reed switch to work, you have bugger all chance of making a hall switch work. They are not interchangeable and they are not magic cure-alls. The folks around here use hall devices for high speed sensing and bicycle wheels are definitely not high speed devices.

Work out why your reed switch system is not working and fix it. Look for broken or corroded wires, air gap too great or changing because of a wobbly wheel or moving switch, or any number of other things.

Just because reed switches are not cool doesn't mean it is not the right device for the job.
--
Bill

 

[cohberg]

They are not interchangeable

Actually yes they are, a reed switch and a hall sensor perform the same task: telling you when the sensor is near a magnetic field.
A hall is just a bit more precise as it tells your how strong the field is instead of the boolean the reed gives you.

The folks around here use hall devices for high speed sensing and bicycle wheels are definitely not high speed devices.

What the hell are you talking about? Hall sensors are built into the majority of hub motors.
Halls tell the controller how fast the hub is spinning. The hub is directly attached to the wheel. Thus, hall sensors tell you the speed/rpm of the bicycle wheel.
Your sentence can be corrected by omitting parts of it: "The folks around here use hall devices for high speed sensing and bicycle wheels."
It doesn't matter how fast the wheel is spinning, the hall sensor will just tell you how strong the magnetic field is at the time.

Just because reed switches are not cool doesn't mean it is not the right device for the job.

Well in my case no. I wanted the speed of the rear wheel as the controller saw it. Its good for debugging and making sure all the halls are working

If you can't get a reed switch to work, you have bugger all chance of making a hall switch work.

Well thank you for the amazing advice that points me towards a solution, your attitude clearly demonstrates a willingness to help not criticize.

To anybody else who is thinking about doing this, I ended up needing an optocoupler between the hall output(5V) and the bike computer sensor input(1.5V) to avoid frying it. But other than that it was just as simple as tapping one of the hall outputs.