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Originally Posted by eugenebrooks
2) With regard to sensor testing, we have used led indicators as
part of the design, so that a quick look can determine if it
is "blinking," software running in the RC that prints a message
each time a sensor value changes, and finally, a scope. There also
relatively cheap multi-meters that have a "frequency display" for
a TTL input level, and you can use these to see if a high pulse
rate sensor is working correctly.
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3) The electrical environment in a robot is very noisy, with lots of
spikes on the power lines. If a sensor requires power from the 12
volt line, we bring that power in through a substantial inductor, a
capacitor bypass, and then on board voltage regulation. We usually
ground a sensor at the RC, instead of elsewhere, to avoid
any ground loops that might introduce spikes into the sensor output.
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I like the LED idea. Especially if we can implement it using the LEDs on the RC. I'm not sure how we were grounded, but I'm pretty sure we did it at the RC. At least there were no extra ground wires running around. We might have had an unintentional ground, but we're pretty good about following good electrical practice (two of our mentors do this stuff for a living and they make sure we do it right) The problem with pots was that they only give 255 "clicks" and we needed 540 to get the resolution we wanted.
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Originally Posted by SlimBoJones
What we didn't account for were "jolts." Momentary hits that moved the encoder just far enough to record a count or two (at 256 ppr, this isn't much movement), and fast enough that the RC would read the quadrature signal incorrectly. The end result was a count going in one direction was being misread in the other direction - this is what happens when you read a quadrature signal too slowly. This caused havoc with our PID loops, which functioned great until you smacked the robot, and things would go haywire until you settled everything down again.
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I'll have to look more closely into just what was happening at failure. We spent a lot of time getting smacked while we were minding our own business stacking tetras. While we are reasonably sure there was not direct contact with the sensor, we haven't evaluated the possibility of shock inducted counts at a high rate.