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Shootable “Simon” Game



WHAT THIS IS

This is a Simon game from Spark Fun Electronics which you play by shooting plexiglass plates with an Airsoft gun instead of tapping buttons with your fingers. It’s fun and playing it well is harder than it looks. This is also one of my ugliest hackjobs. (Between you and me, that’s mostly because I was in a hurry to get it working since I was starting to get bored with the idea. Once I lose interest in a project it rarely goes any further because by then I’ve moved on to something else.)

It did work, and a couple parts are useful for other things – such as the airsoft BB hit sensor circuit.

WHAT IT CONSISTS OF

The Simon game was from Spark Fun, and the shootable plates are made from plexiglass and piezo elements. When a piezo element is subjected to a sudden vibration/jolt/impact (such as when the plexiglass it’s attached to is hit by a BB from an Airsoft gun), electricity flows in the form of a voltage spike. Some simple circuitry is used to detect this and turn it into a digital signal. This digital signal is used to trigger the Simon game’s button input in the place of an actual button.

So in other words, the Simon game works perfectly normally with the exception that instead of pressing a button, you shoot a plexiglass plate with an Airsoft gun.

To make this, you’ll need some electronic parts and tools and some electronics knowledge. If the terms Gate, Drain, Source, Regulated voltage, and Schmitt Trigger don’t mean much to you, you will have trouble doing this project.

Making a plexiglass plate hit sensor
To do this, you’ll need a piezo element, a sheet of plexiglass or similar material, and cyanoacrylate (super) glue.

Your piezo element should look something like this (left).

A good source for them can be cheap electronic toys or gadgets, or other junked equipment.

Superglue the flat face of the piezo element to one side of the plexiglass. This side will become the “back”; you’ll shoot the “front” (i.e. the side that the piezo element isn’t on).

If you’re modifying the Simon game, you’ll need 4 of these.

Making the piezo sensor
If you’re modifying the Simon game, you’ll need 4 of these (1 for each piezo hit sensor).

You’ll need the following parts:

  • 74HC14 Schmitt Trigger Hex Inverter
  • 1N4148 diode
  • 4.7M resistor
  • 10k resistor
  • and a ZVN2106A FET

Here is the schematic for the circuit, including the connection to the piezo hit sensor. For testing, you can connect an LED between pins 3 and 4 of the 74HC14. Giving the plexiglass plate a good smack should either light or unlight the LED (depending on which way around you installed it).

You’ll need 4 of these for a modification of a Simon game (1 per switch to actuate). In the case of the Spark Fun Simon game I used, the “/HIT OUT” would be connected to a switch input on the Simon PCB.

Modifying the Simon Game
I used the Simon game from Spark Fun, but you can use almost anything you want as long as you can trigger the buttons by applying a logical 0 or 1 to the right pin or contact. In my Simon’s case, applying GND to the inner ring of the button contact does the trick. A logical 0 sent here will “push” the button.

First, I de-soldered each LED under the button panel and extended them out on wires. I did this in order to have each LED shine on its matching plexiglass panel, instead of lighting the button.

Next I soldered a wire from each button contact to each of the outputs of the piezo hit sensors. This is so that when the panel is shot, the LOW from the 74HC14 gets fed into the button input on the Simon game which triggers the input.Therefore, shooting the panel is the same as pressing the button.


Bottom of the Spark Fun “Simon” game.


LEDs have been desoldered and extended out on wires, and wires attached to Simon’s power supply.


Blue wires connect to the button inputs. Applying GND to these connections “pushes” the applicable button.

Power Supply
I powered the piezo hit sensors from the +5V supply of the Simon game, but if you supply the hit sensors with a separate power source, remember to tie together the GND of both power supplies (that is, your piezo sensor’s power supply GND should be connected to the (-) of the battery connector on the Simon.) Note: Only connect the GNDs! Do not connect the (+) of the two supplies!

Mounting
This is where mine got ugly. I drilled some holes in the plexiglass, tied them to a dowel, and hot-glued on the small sensor circuitboards. Ugly, but functional. Here is the basic layout. Each plate got one of the LEDs as well, making sure to match up the right LEDs to the right inputs.

Using it
Using it is straightforward of course, but make sure you only use it somewhere that flying and ricocheting Airsoft BBs will not be a problem. Angle the plexiglass plates so that the BBs ricochet off at a safe angle (for example, downwards into a box with a towel). Always remember to wear eye protection. A video of a short demo is below – I only make it to 3 shots before I screwed up.

LESSONS LEARNED

  1. A pretty good airsoft BB hit sensor can be made with a piezo element on a piece of plexiglass.
  2. Not all piezo elements are created equal. Some were more sensitive than others – a tap of my finger would trigger some while for others I had to smack a hefty screwdriver onto it to get a reaction. However, they all seemed to detect BB hits reliably.
  3. It’s easy to underestimate some things. I expected this to be a project for a few evenings but it wound up taking much more time than that.
  4. Plexiglass won’t stand up well to repeated close-range BB hits. If it’s cracking, breaks won’t be far behind…