View Single Post
  #7   Spotlight this post!  
Unread 13-02-2006, 15:58
Dale(294engr]'s Avatar
Dale(294engr] Dale(294engr] is offline
Mentor/Sponsor since '98
FRC #0294 (Beach Cities Robotics)
Team Role: Engineer
 
Join Date: Jan 2004
Rookie Year: 1998
Location: Redondo Beach, CA
Posts: 92
Dale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of light
Re: Tach-like Sensor

Quote:
Originally Posted by BillyJ
Thanks for the quick replys and options. I think we're pretty much set on using the tape on the wheel since it would be the easiest to implement at this point.

Could anybody recommend something that would be better then what I had before?
Team 294 is using the KOP VISIBLE Banner sensor to measure shooting wheel speed 20% black on white (checked out with margin at 100 rps = 6000rpm)

Team 294 is using the KOP IR Banner sensor(s) to measure ball exit velocity (IR reflected from exiting ball), one IR sensor at wheel exit, one at 1m (up to ~1' away detection range) using any BUT black half balls (blue/green, purple/green, anything but half black which absorbs IR). This (& pulsewidth below) method have proven very accurate & reliable and the sensors are well up to the speeds. (not close to limit)

We are viewing the pulse waveforms on an oscilloscope.
A 'C' program could be written to do the job of recording the data and results.

83 mS (.08333s) between 1 meter spaced sensors is 12m/s (1/.08333s)
or use exit sensor leading to training edge pulsewidth and factor in number 7" ball width in a meter.

Vexit_m/s = 1/((39.37"/m / 7"/poof ball = ~5.624) * pulsewidth)

12 m/s
83.3 mS / 5.624 = 14.8mS pulsewidth_7"ball, expected

Dale (294engr]