plinko - puck tracing with magnetic switches

Hi all,
I am making a Plinko board and am trying to figure out a way to light up the path that the puck takes as it falls down the board. I was thinking about burying magnetic sensors like one of these (|0) inside of each peg, and then installing a high strength magnet (or several) inside of the puck so that as it bounces off of the pegs, it activates the switches. An arduino could read the output of these switches via a centipede shield ( and then I could light up LEDs inside of the pegs (clear acrylic) for each peg that has been activated. There are 58 pegs total, so quite a lot of inputs and outputs needed. (106 total) so I was thinking about using two arduinos with centipede shields to run this apparatus. Does this sound feasible? Is there an easier/better way to do it? Any advice on what magnetic sensor to buy for this application - the options are overwhelming! Thanks!!!

Just spitballin'. A puck implies something shaped like a hockey puck. Given that: the puck has a conducting band on the circumference. The peg has two contacts, like a mono headphone jack, which form a closed switch when the puck edge contacts the peg. Debounce and interpret the switch closure to turn on the LED.


This exact idea was originally what I had planned, but it seemed like a lot of work to fabricate 58 pegs and I couldn't figure out how to cleanly produce the split contacts with associated wiring and to make it look good. I thought that the magnetic switches would be an easier/cleaner install...if they will work :)

Hmm, interesting problem...
I guess you don't want the pegs to move at all (so any sort of 'trembler switch' is out), they want to be rigidly fixed so the puck bounces off (so a piezo 'knock detector' might trigger from an adjacent peg), but you really want the peg to light up only when it is actually hit (so magnetic might trigger on a near miss).

Seems to imply some sort of actual contact detection is needed.

dougp's 'like a jack plug' with the puck making contact sounds about the simplest you could get from an electrical point of view (you could use the weak pull-up facility on the Centipede Shield and short the pin to GND, maybe add a small capacitor like 1nF so the low-going pulse is longer). Might need something like conductive rubber around the edge of the puck.

If the pins are acrylic, you could wrap it in copper tape (Google 'slug tape'), then push the pin copper-end first thru the board and glue it in place. If the connection to the top band and the tape joins are on the bottom of the pin it could look real neat.


How about a magnetic reed switch inserted up the middle of each peg that would be connected when the puk magnet got close enough?

"close enough" is not necessarily a touch.

I'm thinking of (piezo) impact sensors and then have the rod attached to those sensors, but not to the board itself. But maybe those need a too hard hit to be reliable, or be too sensitive to general vibrations in the rig?

How big is the puck field? If only one puck is falling at a time, you could use a simple xy matrix of IR leds & optos to detect the passage of the puck through any ‘square’. Then trigger the light in that cell as needed. You could do some nice comet-tail effects too.

Hi, Using the pegs would be a problem as the puck could be either side of the peg so that is two different paths it could be taking.

LDR or IR sensor between each peg would give a definite path indication.

Tom... :)

My thoughts are to put a light sensor in the space between the pins. When the puck covers the light sensor we know the path. Much much easier then trying to create special pins And since you may want to put lights in that same space you are already wiring them and putting holes in the face of the game board.

And reading that Tom had posted the exact same thing makes this post look redundant

So you didn't like the idea of a matrix?

And reading that Tom had posted the exact same thing makes this post look redundant

Its alright mate… Great Minds Think Alike… :o