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Unread 26-01-2006, 10:10
Tom Bottiglieri Tom Bottiglieri is offline
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Re: Speed Sensor for Ball Shooter

Quote:
Originally Posted by Don Wright
There could be a problem if you are trying to use a lot of encoders. i.e. two shooter wheels running at ~2000 rpm, and 4 drivewheels and whatever else. You "could get the red light of death" as our programmer calls it when you are servicing interrupts so often...


http://www.eidusa.com/Interface_Boards_F_to_V.htm
The two shooter wheels shouldn't be a problem programming wise. Based solely on implications, I'm assuming you dont care how slow your roller is spinning, you care how fast your roller is spinning. Therefore, unlike in a drivetrain, you can easily get away with a non directional, 1 PPR encoder type switch. (As easy as a light sensor picking up a piece of relefective tape on a shaft!)

You can use this because you are only trying to determine a relative (to the other roller, or to a standard you set) velocity for each roller. Even at 2000 RPM, a simple "1 tick" sensor would pulse ~33 times per second. This will run pretty parallel to the loop in the default program. So, yes you are using an interrupt, but no, it is not taxing the processor anymore than a few commands in the default routine would. You can even determine actual velocity by using a timer to look at the times between interrupts.