[Bneufeld235]

We received a lot of great feed-back from talking to teams at Championships. Most questions fell under two categories: maximum performances and testing.

We have done testing at relatively low speeds so we are unable at this time to give a maximum speed. That being said, we calculated theoretical maximums based on the slew rate of our op-amps and are convinced we will never be able to test the maximum rate.

We realize that is a bold claim so here are some numbers. We have designed this to trigger at TTL levels but our worst case scenario is making every max voltage go from zero to maximum supply voltage to zero 111,000 transitions or 55,500 cycles per second. The default striped resolution is 0.2" (5mm) has 20 stripes around a 2.5" diameter hub. This would correspond to a speed of 166,000 rpm.

Absolute max performance is a signal that just trips the hysteresis with a much higher 500,000 transitions which is an approximate 750,000 rpm. This is theoretical in a perfect world and will not be any where close to that.

It should be noted that this is at default low resolution. The arbitrary part of the encoder is the resolution as well as the count per revolution. Higher resolution can be achieved by skewing the encoder. We will produce a table of stripe size to skew angle and post this once we verify performance.

We have posted this to receive feed-back from other FIRST teams so if you have any questions please ask.