Anyone know of a good Impact Sensor for ball strikes

[Entropy42]

I want to make something like this (http://www.knockoutnet.com/how-it-works.html) for my basement, but I don't know what kind of sensor to use.  It's basically a grid of 9 plastic panels and you shoot a puck at it or throw a ball, and I want it to register which panel gets hit.  I think I can figure out how to make the physical structure and a Raspberry Pi for the control electronics, but my google searches did not turn up an arcade sensor that would do what I wanted.  I know it must exist though, there are enough games out there that operate on a similar principle.  Hoping someone here can point me at a good option.

[PL1]

I don't know of any pre-fab sensors for that type of setup, but you might be able to make something like this:

- Surround the plastic panels with welded U-channel mild steel.
-- If you want to make it easy to replace the plastic, use U-channel on the top and sides and a flat bar on the back with screws that go horizontally below the plastic.  Remove the screws to pull out the plastic.

- Piano hinge on the top of the panel surround.  Hinge point must be forward of the panel's center of gravity.

- A 3x3 grid of horizontal L-shaped mild steel (red) to attach the piano hinges, vertical bar stock for spacing, and square tube for a solid outer frame.
-- The panels should be mounted so the bottom can swing back a small distance and gravity returns it so the bottom is slightly forward of vertical.
-- Consider mounting the L-shaped pieces so the front is 5-10(?) degrees lower than the back.  This gives more travel for the hinges, but makes it a little harder to cut the bar stock.
-- Add sturdy stops for the lower corners of each panel to keep the panel from swinging too far back.
-- Lever arm (or roller arm) microswitches on adjustable mounts positioned so the frame striles the arm (or roller) and the stops keep the frame from crushing the switch.

Side view:           XX   stops and switches
                          XX    for the panel above
              ------------|
piano     /---------    |        ==> back
hinge   O                  |
             \---------    |
                panel       |

- A removable front bezel that keeps the panels from travelling too far forward.
-- Remove it to swing panels forward and replace the plastic.


Scott

[RandyT]

Piezo discs are used in electronic drum pads for impact sensing.  I would imagine that they could be used equally well in an application like this.  The only caveat is that you would want to isolate each panel for vibration as well as possible from neighboring panels, and build something into your software/firmware to tune the sensitivity. 

[Entropy42]

Thanks for the ideas guys.  I don't think the hinge system would really work for this application, but those piezo discs seem like what I'm after.  They seem to output a voltage pulse proportional to the impact force, so hopefully I can find a tuned setting that triggers off impacts but not a neighboring panel.  I planned to make 9 panels each separated by about 1/4", and suspended on foam gaskets for damping.

[RandyT]

...hopefully I can find a tuned setting that triggers off impacts but not a neighboring panel.

Well, you have one good advantage going for you in this application.  On a drum kit, multiple simultaneous drum hits are valid and expected.  In your case, you should be able to consider only the strongest signal a "hit" and ignore the rest.