I have downloaded the specs for the Black Jaguar to research exactly that question. The spec sheet claims 1 million transitions per second. So the 250 counts per revolution is 4 transitions per line, so 1000 transitions per second. That means that it should handle 1,000 revolutions per second, or 60,000 RPM.
My problem is getting a feedback signal to the Jaguar. Currently I have a left over magnetic encoder, but so far the Jaguar has refused to display a speed or position signal from the magnetic encoder output, which means the PID just ramps up until the Jaguar limits out.
Mike
Quote:
Originally Posted by Jared341
Regarding speed sensors: An encoder is a good fit for this task. However, keep in mind how fast your wheel will be spinning.
Let's say your shooter is powered by a CIM and a 1:1 ratio. You will see ~5000rpm speed on the shooter wheel.
5000rpm is 83.3 revolutions per second. If you use the kit of parts encoders (250 counts per rev), that is more than 20,000 counts per second. In theory, the FPGA can count upwards of 39,000 counts per second. So this arrangement would work if you are doing speed control on the cRIO, but if you wanted to go to, say 10,000rpm on the shooter wheel, you would want a lower resolution encoder. I am not sure about the capabilities of a CAN Jaguar when it comes to maximum encoder rate.
In 2006, we made our own encoder by using an IR reflective sensor (like the ones Banner or Rockwell makes) with strips of reflective tape on the shooter wheel to trigger the counting. This method would of course work in 2012, as well.
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