At the risk of asking a dumb question - do you get one pulse per black spoke, say, or one pulse for a black and one for a white? I.E. Should my 44-spoke disks produce 44 or 88 pulses per rev?
~Mike
Mike,
On the contrary, that's a very good question, and one that I'm sure many customers would like to know. :)
Speaking of how the Serializer sees encoder interrupts, it sees a transition from white to black as an interrupt. Thus if you have 44 black spokes, and 44 white spokes, you will get 44 interrupts.
I would've liked to have had an interrupt occur on any level transition (white-to-black or black-to-white), thus doubling the encoder resolution. However, one of the interruptable encoder pins we use on the PIC can only see interrupts in one direction or the other, but not both. Thus we had to follow that behavior on both interruptable pins.
Now, the actual encoder modules output 0-5-0-5 transitions based on the color it sees. So, if you were using a chip that has two interrupts which can interrupt on any level transition, then you could then double your resolution. Of course, you couldn't take advantage of the power of the Serializer libraries and services at that point, and have to develop your own code to handle that to run on that chip.
Well, I've made some progress.
I used that encoder designer program to create a pattern. I went for a 3.5" diameter to give at least a little extra clearance (with the 4" wheels). About the densest I could get to draw fairly cleanly was 100.
I printed these out onto clear vinyl self-adhesive label stock, and gave them a few coats of clear acrylic to seal and protect the ink. Then I applied them to a pair of disks I made from some white polystyrene I had left over from some vacuum-forming projects. Now I just need to make a couple of brackets to position the encoder boards and it should be good-to-go.
100 resolution will give me about 180 clicks per second. Is this still too small a number of clicks? If so, what's the threshold of clicks per second that would be useful?
Mike, Take a look at
http://www.usdigital.com/products/e4p/
300 counts per revolution for $19 each. just make sure the Diameter will fit your motors.
Ringo