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Registered Member #3781
Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701
One of my teachers has a class where he has his stuents design and build styrofoam airplane's powered by one electric motor and then attaches them to a pole that can swivel around Thus, when the motors are powered, the plane will hopefully fly around in a circle. If the plane gets off the ground the student gets credit for the assignment. However my teacher asked me if I could rig up an accurate timing system that would display the amount of time (in seconds) it takes for the plane to make a revolution around the pole. So since there's a gap between the stationary pole and rotating top, I figured I could use a magnetic reed switch.
Unfortunately I have not had any experience with timing circuits that use a digital display and was wondering if someone could link me to a schematic that would work or at least point me in the right direction. It only needs to display the time it took for the fastest revolution around the pole and would prefferably be run off of a 9v or AA batteries.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Nice pictures there. I like the use of a telephone cord rotary joint for, apparently, sending power to the airplane.
A hardware-only rotation timer would be relatively ambitious and time-consuming. Especially if durable, so your teacher can use it for years. How about using a microcontroller?
For kluge cred, use a standard "cyclocomputer" (digital bicycle speedometer). The kind with a reed switch activated by magnet on a spoke. It gives average and maximum speed. If you can't get one that registers on a single wheel rotation, then the fun part is instrumenting your airplane pole for multiple pulses per rotation. Time for other 4hvers to weigh in.
Be sure to check out tether-car technology. Maybe some club member can point you to a timer product, or standard design.
Registered Member #4465
Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145
Of course, a small PIC project it seems to be the perfect solution, however, just to make one idea about the classical hardware implementation, see the attached diagram.
Registered Member #3781
Joined: Sat Mar 26 2011, 02:25AM
Location:
Posts: 701
Ah thanks for the help! I'm going to talk to my teacher about it tomorrow but I'm leaning toward Arduino, however the bike speedometer is a good idea if he doesn't have a big budget... Nice video too Kludgesmith
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Magnetic Reed Switch Timing Circuit
