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I'm working on a project for school, and wondering what options I have for detecting the corn bags through a piece of wood.

Examples of pieces of wood used in cornhole game

More specifically, we are creating an automated cornhole scorer.

Example of a manual cornhole scorer

Sources of images are those: wood and scorer.

We have chosen to some sort of load sensor for the bags within the hole, but still looking for options to score the bags that lie on top of the board. We have looked into some openCV application, which is most likely what we are to use.

Being an electrical engineer, I am still trying to figure out different ways we can detect the bags without a camera. Accelerometers have crossed my mind, but the angle due to the ground can be compromised easily. Having PCBs in every bag can get quite expensive since they will also have to transmit the data wirelessly.

Is there any sensor that can detect multiple objects with just magnets inside of each bag?

Ricardo
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user39948
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    Have you considered a load cell or 3 at the bottom of the box? – Ignacio Vazquez-Abrams Apr 06 '14 at 19:38
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    Agreed. Two load cells. One on a platform that the bags that land in the hole, and another for the rest of the box. – Passerby Apr 06 '14 at 19:39
  • It seems the easiest way to do this would just be an optointerrupter right at the hole. Each bag would trigger the optointerrupter once. – Connor Wolf Apr 06 '14 at 22:57
  • Hell, just have the hole blocked by a piece of material, on the end of a momentary switch's arm. The bag will depress the material on it's way through the hole. – Connor Wolf Apr 06 '14 at 22:59
  • Blast the bags with microwaves, and count the popping sounds? :-) – gwideman Apr 07 '14 at 02:41
  • I knew a guy that was trying to do this exact project. He embedded RFID tags in the bags to identify the team. That probably won't help you determine whether the bag is on the board. I don't know if his project was ever successful. – Matt Young Apr 07 '14 at 02:54
  • @connerwolf that only addresses the ones that go in, but not the ones that land on the outside. – Passerby Apr 07 '14 at 03:06
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    To respondents who didn't notice: OP has already figured out how to count bags that go through the hole. He/she wants to count the bags that land on the face of the cabinet. – gwideman Apr 07 '14 at 05:35

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I can't think of a magnetic way to do this, but how about capacitive? The problem at hand is very much like that solved by a capacitive touch sensor. The upper panel of the cabinet could be lined with a grid of wires or conductive tape, and touch detector circuitry and software could find the number of blobs sitting on top. Search google images for "capacitive multi-touch sensor grid" for examples.

Samples: http://www.mouser.com/applications/touch_touchscreen_technology/ https://igw.tuwien.ac.at/ceat/

But I'm favoring the load-cell suggestion already made. You would probably need one on each corner supporting the upper cabinet panel, so that together they weigh the bags evenly regardless of where they land.

gwideman
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To detect bags resting on the surface, I would wonder about piezoelectric impact sensors, or about putting some ferrite beads in the bags and putring coils under the wood to detect inductance change.

Roman black has an algorithm for determining the location of a tap with three microphones using time difference of arrival.

http://www.romanblack.com/SonicRanging/Sonic_Ranging.htm

EternityForest
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  • One problem with this is that initial impact position can be drastically different than final position if it slides at all. – Joe Apr 07 '14 at 14:22