Gear tooth sensor

[chiu.steven]

I have no idea how to program or even to run the gear tooth sensor. What does it do and how do you program it in LabVIEW?

[DonRotolo]

The short version is that it is a magnetic sensor. Every time a piece of ferrous* metal gets within about 2 millimeters of it, the output changes from a low level (around 0 volts) to a high level (around 5 volts)(AKA 0 and 1 to you digital folks). To every time a gear (or sprocket) tooth passes, you get a pulse, for example. If your sprocket has 24 teeth, you get 24 pulses per revolution.

You just count the pulses, and that tells you the number of rotations. Doesn't tell you the direction. Doesn't help if a wheel is slipping (and that's what you are measuring).

Also, if the wheel speed sensor is from a previous year's Kit of Parts, I would check the rules to see if it it legal to use, since I don't think they are considered COTS items.

[daltore]

If they aren't COTS, you can make your own with commercially bought hall effect sensors (they look like transistors, just google "magnetometer" and you'll get results). With the individual sensors themselves being so small, you could actually probably place two of them close enough together to get a directional output (because you could measure rising edge and falling edge by doing some subtraction of the two voltages, i.e. if(hall1-hall2 < 0) direction=forward) It's a little more complicated than that obviously, because timing is so important, but given some thought, it should be fairly simple. The sensor cells are a couple bucks a piece.

[DSST\neal.ian]

He was talking about the encoder, and we figured it out. Thanks, and see you tomorrow, Chiubacca.