Kids Carnival Game -- Speed Ball

Tony B

Every year I build a carnival game for my kids school; past games have been a Ring Toss, Lolly Pop Pull, a Live Wire game where the kids try to move a circle along a wiggly wire without touching it, if they do – BUZZzzzzz, and a Roulette looking wheel that they spin to win tokens, candy and the grand prize of a gigantic pickle – some thing I will never understand.

I would like my next project to be device where the speed of a ball thrown by the kids is measured. They get three attempts, after the first two, they need to correctly guess the speed of the third. If they are correct, they win the tokens.

Speed will be measured by taking the time difference as the ball passes between two sensors – say three feet apart. If we can measure the time between the two sensors, it can easily be converted to MPH with some basic math.
Seconds = Milliseconds /1000
FPS = 3 / Time in seconds between sensors
MPH = FPS * .68181

For example: It takes 35 milliseconds for the ball to pass between two sensors. This equates to:
.035 seconds
85.714 FPS, and
58.44 MPH

Times between sensors could be as low as 18.5 milliseconds for a speed of 110/MPH

The results may be presented by a voice module, and/or either a LCD Display or the SX Video Module.

My questions are – in no particular order:
Which Stamp processor should I use?
Is there a sensor, that is not cost prohibitive, that can detect a baseball being thrown past it?

Any assistance, advice or suggestions will be greatly appreciated.

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Every problem has a solution. Some don't even create more problems.

bubblehead

Here's two ideas:

each uses two pieces of plywood three feet apart with circles cut in them to throw the balls throw

idea 1: laser pointer, two narrow mirrors, and a detector mounted to the back side of the plywood. The lasers and mirrors are arranged so that the laser is made to bounce back and forth across the opening many times and then hit the sensor. The laser beam should cross enough times to ensure the ball can't pass through the opening without breaking the beam. The detector detects when the beam is broken.

idea 2: get one of those line projecting laser lens assemblies and set it up so that is projects a "curtain" across the opening in the plywood. When the ball passes through, it will reflect the laser back toward a detector.

Paul Baker

In the interest of keeping things simple, reliable and easy to setup; how about modifying the setup abit to emulate a skeet-ball game? You would have a channel that the ball would be rolled up, that way you could use simple IR beam iterruption to detect the speed.

If you really want the thrown ball setup, you could use a single sheet of plywood with a cut out, a row of IR pairs, and use some logic gates to accumulate all the outputs so that when one beam is broken the output is shown as broken. Then you would measure the width of the "broken" pulse, and using the diameter of the ball as reference you can determine the speed of the ball by how long it interuppted the beam.

These are the units for PULSIN for the various BSs.
BS1·· ·BS2·· BS2e· BS2sx·· BS2p
10 μs·· 2 μs···2 μs··· 0.8 μs··· 0.75 μs
If a softball were used (~3.5" diameter), a 2µs beam interruption corresponds to 1.75"/µs or ~27 mph, which isn't enough. Using the BS2p it goes up to 73 mph. If you use a double row of plywood where the second set of beams would be interrupted before the second set is cleared (ie space between sheets is less than the diameter of the ball), you could increase the measurable speed and the granularity of the measurable speeds.

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1+1=10

PJAllen

Speedy radar kit -- http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=SG7· It could probably be Stampified.