Not urgent but idk if one is illegal. Some of our optical encoders have two wire systems, others only have 1. I don’t really know the difference, if anyone can help, it would be greatly appreciated.
So the ones with 1 wire are “shaft encoders” and the ones with 2 wires are technically “quadrature encoders”. The 1 wire versions are older and would only be legal if their part is listed under R6(c) or on the vex discontinued parts list (or if their part number matches the part number of the 2 wire version).
There are 2 main differences. The one with 1 wire has 90 ticks/rev and the one with 2 wires has 360 ticks/rev. This is because a second IR sensor is connected via the second wire. This means the quad encoder has much higher resolution than the regular shaft encoder (+/- 1 degree of accuracy vs +/- 4 degrees of accuracy).
The 2 wire version can also tell the brain what direction the shaft is spinning. This is because the 2 sensors are 90 degrees out of phase — taken together they either lead with a 1 or lead with a 0, which is either forward or backward. This makes the newer version much more effective for odometer because the tick count the brain keeps through an interrupt knows when to add or subtract from the total tick count rather than just always adding. It is very very difficult to use the old version for odom because you either have to ensure it always spins one way or create a task to handle the interrupt process yourself and add in the directional information using some other sensor/assumption.
TL;DR the second wire is for a second IR sensor increasing resolution and adding directional information.
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wow, this is extremely helpful. Thank you!
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As @le_manchot said, the one wire encoders would only be legal if they are listed on the discontinued products page here:
Unfortunately for some reason the page has no details about many of the products listed and a number even don’t have pictures, so it’s hard to tell if a specific product is listed or not. The only potential for the one wire encoders that I see would be the advanced sensor kit, which has this tiny picture:
I can’t really tell from that picture whether the encoders in it are one or two wire.
@DRow any chance we could get bigger pictures and maybe some details of each product listed on that page?
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