Building a very tall PID control ping-pong levitation tube.
Closed loop, with blower speed control.
Tube- 20 feet of vertical pyrex tube, made in joined sections, 42 mm ID
Ball - Standard Ping Pong ball
I need to figure out a way to get solid position feedback with the following specs:
10 readings / second or more
Resolution- 9 bits or better
Accuracy - 2 inches- not terribly critical.
Power- not critical, AC is available
The ball will be illuminated by a powerful (300 mw /color) RGB laser engine, with PWM brightness control, this might cause problems with laser-based ranging systems?
It is preferred to accomplish ranging AND illumination from the bottom of the tube.
I was hoping to use a simple ultrasonic ranger, but after researching the physics a bit, it seems that
short sound wavelengths don't like long tubes.
Thinking I might be able to use low frequency sound pings, the same way that the ultrasound units work, but
at a lower frequency (4khz) that will propagate in a 42 mm tube? The thinking here is that I could use an inexpensive tweeter and a tiny capacitor microphone to accomplish this cheaply.
To get good return echos, I might need to increase the acoustic impedance of the ball by coating the inside with some resin.
Any ideas?
Closed loop, with blower speed control.
Tube- 20 feet of vertical pyrex tube, made in joined sections, 42 mm ID
Ball - Standard Ping Pong ball
I need to figure out a way to get solid position feedback with the following specs:
10 readings / second or more
Resolution- 9 bits or better
Accuracy - 2 inches- not terribly critical.
Power- not critical, AC is available
The ball will be illuminated by a powerful (300 mw /color) RGB laser engine, with PWM brightness control, this might cause problems with laser-based ranging systems?
It is preferred to accomplish ranging AND illumination from the bottom of the tube.
I was hoping to use a simple ultrasonic ranger, but after researching the physics a bit, it seems that
short sound wavelengths don't like long tubes.
Thinking I might be able to use low frequency sound pings, the same way that the ultrasound units work, but
at a lower frequency (4khz) that will propagate in a 42 mm tube? The thinking here is that I could use an inexpensive tweeter and a tiny capacitor microphone to accomplish this cheaply.
To get good return echos, I might need to increase the acoustic impedance of the ball by coating the inside with some resin.
Any ideas?