Sensor Question - Detect A Passing Golf Ball From One Side

Hello All,

This is my 1st post here as I am pretty much new to electronics design, but have followed other's schematics, built and & programmed PICs projects.

My problem is this, I have a design project in mind but am unsure as to the best kind of sensors to use. Essentially I want the project to be housed in a box that you can place the box on the floor (or golf putting green) and putt a golf ball past it at a distance of say 4-12 inches / 100-300mm. The circuit would have 2 sensors and a timer under PIC control - hence able to measure the speed of the golf ball (nothing bigger than 30 mph / 48 kph I would guess) and display it on a LCD.

Now, I dont want a broken beam approach as then you have to have 2 halves or breakouts etc. So, I was thinking about IR Led emitter detector sensors like this one, the SHARP GP2D15 (**broken link removed**) rather than building a "sensor system" out of discreet components.

Am I going about this the right way? Is there any other way (ultrasonics seem a tad too expensive)? Your thoughts & comments are greatly appreciated.

Dave
Lancashire
England
aka Space.Invader

Re: Sensor Question - Detect A Passing Golf Ball From One Si

Space.Invader said:

Hello All,

This is my 1st post here as I am pretty much new to electronics design, but have followed other's schematics, built and & programmed PICs projects.

My problem is this, I have a design project in mind but am unsure as to the best kind of sensors to use. Essentially I want the project to be housed in a box that you can place the box on the floor (or golf putting green) and putt a golf ball past it at a distance of say 4-12 inches / 100-300mm. The circuit would have 2 sensors and a timer under PIC control - hence able to measure the speed of the golf ball (nothing bigger than 30 mph / 48 kph I would guess) and display it on a LCD.

Now, I dont want a broken beam approach as then you have to have 2 halves or breakouts etc. So, I was thinking about IR Led emitter detector sensors like this one, the SHARP GP2D15 (**broken link removed**) rather than building a "sensor system" out of discreet components.

Am I going about this the right way? Is there any other way (ultrasonics seem a tad too expensive)? Your thoughts & comments are greatly appreciated.

Dave
Lancashire
England
aka Space.Invader

Click to expand...

I think ultrasonics will be more complicated. The problem is at those distances (several inches/hundreds mm) Proximity and ultrasonic sensing get very complex.

Are you sure you can't live with the broken beam approach? It is perfectly suited for the task. If you absolutely cannot live with broken beam consider the following:

You might have some luck with several IR emmiters and one IR photo transistor. If you blast lots of IR towards the path to be cut (by the ball) and run the photo-tran in the linear range (some extra circuit complexity), you just might be able to resolve the change in output(from the very fast photo detector trans) when the ball actually breaks the beam and reflects some of the IR toward the sensor.

Generally though, you will need LOTS of IR output and high sensitivity on sensing the reflection. I will be a non trivial signal to noise ratio problem and I dont know if it is even practical to try when approaching 12 inches.

Unfortunately the ball will reflect light in all directions off of that side of its surface where only a small amount will land on your sensor. Consider multiple sensors and "calibrate" it with no ball present and then look for the smallest change in any/all of them for sensing the ball.

they make light chronographs for paintball. they are very sensitive to ambient lighting, and they generall don't work very well, but they do detect a paintball (which is a lot smaller than a golf ball) moving at velocities of around 300 feet per second... the typical area for sensing is about 6" or so above the unit...