Author Topic: Electronic Dartboard (what sensor we are going to use?)  (Read 4337 times)

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Offline juriesnake

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Electronic Dartboard (what sensor we are going to use?)
« on: February 26, 2014, 08:44:01 am »
We are going to make a Thesis Project "Electronic Dartboard" which features automatic score that will be displayed in a 7segment once it detects a dart pin on its dartboard. My problem is what kind of sensor we're going to use. Can you please give me some suggestions?

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Offline fcb

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #1 on: February 26, 2014, 09:10:51 am »
Depends on your comfort-level & ability with software.

I can think of at least a half-dozen ways to do it - but if I was doing it, I think I would use microphones around (at least 6) the edge and look at the relative timing of the thwack.

Regulation board is 451mm diameter, speed of sound 340.29m/s so you could do it quite crudely using the time difference between opposite pairs of microphones to create chords, some (very) simple signal processing and three timers on a micro-controller.

Offline minibutmany

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #2 on: February 26, 2014, 09:31:33 am »
Why not use capacitive sensors?
 

Offline TerraHertz

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #3 on: February 26, 2014, 10:31:10 am »
Sounds like quite a hard problem. You can't use anything in the actual target area (the whole board), since
a. Any sensor will get repeatedly stabbed to death.
b. Putting anything other than the usual soft board there will negatively affect the 'thunk-nature' of the board, and detract from the game.

So it's a remote sensing problem. You have to detect the location of several metal pins (the dart needles) within an area, to high accuracy.
The darts may rest at angles, but it's the point of penetration that counts, so you have to sense at (or very close to) the surface of the board.
RF/electromagnetic/radar solutions are complicated by the wide variety of dart body materials, ranging from mostly plastic, to all metallic.

Best I can think of is two or more hi-res cameras looking at the board surface from oblique angles, and some distance away. Then it becomes an image recognition software problem. A fairly hard one, due to angled darts, different body shapes, and darts close to each other.
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Offline sonnytiger

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #4 on: February 26, 2014, 10:38:03 am »
I quite like the microphone idea, seems like the one that would be most likely to work and would be the best trade of between difficulty of implementation and accuracy.
 


Offline Skimask

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #6 on: February 26, 2014, 11:40:33 am »
No kidding...  $15USD for a cheap electronic dart board.
Is even a single hour of design, building, troubleshooting, finishing a dart board worth $15?  (assuming a guy could magically do it all inside of an hour)
I'd doubt if 99% of the population on these forums could do a blinky from scratch in under an hour and under $15.
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Offline fcb

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #7 on: February 26, 2014, 12:44:34 pm »
Can you use real darts in those electronic dartboards though?

Online ajb

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #8 on: February 27, 2014, 05:21:23 am »
Not that I'm an expert, but the electronic dart boards I've seen have used a perforated plastic surface on the target and the darts have blunt plastic tips that are meant to lodge into the holes and make a mechanical contact through the surface.  In practice, they simply bounce off the target as often as stick in a hole.  A proper dart board that happened to have electronic scoring with real darts would be pretty cool.  "Thwack" timing would probably be the way I'd go, but I wonder if you'd be able to get sufficient precision to have reliable judging of darts that land right near a scoring boundary, especially if using a natural cork board that will likely have internal material/density variations that may affect acoustics.  Probably need a manual override to allow for human judgement calls in any case.
 

Offline C

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #9 on: February 27, 2014, 07:07:54 am »
I like fcb's sound idea.

I just wonder if one type of sensor is enough?

I was wondering if you put an array of wire loops behind the board if you could detect the dart tip being inside the loop. Some what like a medal detector but with many loops. With the dart tip being medal it should change the loops properties, but would it be enough to detect?

C
 

Offline deth502

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #10 on: February 27, 2014, 07:42:49 am »
soft tip darts work on sisal boards too. most bars dont even allow steel tip darts anymore. the only boards you NEED steel for are the lowest quality pos rolled paper or cork boards.
 

Online NiHaoMike

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #11 on: February 27, 2014, 07:47:11 am »
What about a piezo behind each "zone" and take measures to minimize crosstalk?
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Offline psycho0815

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #12 on: February 27, 2014, 09:50:42 pm »
Now this is just an idea, but if you place accelerometer behind the board in a grid pattern, i reckon you should be able to extrapolate the impact area. I also like the microphone idea, but i'm thinking it would'n be very reliable in a bar with high ambient noise.
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Offline fcb

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #13 on: February 28, 2014, 12:00:13 am »
As this project is for the OP's thesis, I think they should work out (or god forbid - actually experiment!) the pro's and con's of any proposed method.

That said..

Ambient noise would probably be common-mode enough to not be a major issue.  Also, if the microphones where aimed inwards then they might be better protected against rogue darts and probably increase ambient vs wanted SNR (at the expense of ambient common-mode rejection).

The OP should really just buy a few $1 condenser mikes, a dartboard, borrow a scope and ..... experiment.

Offline psycho0815

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #14 on: February 28, 2014, 12:32:40 am »
i gues i didn't phrase that right. i wasn't thinking about actual ambient noise, but about peaks other than the thwack of the dart, like someone breaking a glas.
As i said i have no clue, how much of an issue that would actually be. I think you really have to experiment to find out.
It shouldn't take much to put together a proof of concept, though.
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Offline Stonent

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Re: Electronic Dartboard (what sensor we are going to use?)
« Reply #15 on: February 28, 2014, 12:54:41 am »
Well one thing to consider, you don't need to know the exact position of the dart, just the scoring zone in which it landed.
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