Lightning Reaction

May 5, 2011


While working with a Basic Stamp 2 for a Tech Ed class assignment, I was bored with the pointless programming task given to me so I decided to program a reaction game (two buttons and a light were given out in class, could not do much more really). Thus I programmed a reaction game (with fair timing) and connected two buttons and a timing light to the BS2. After playing it with a few people, someone said "Hey, you should make it so it shocks people!!!", probably referring back to the ball of power I've shown to the class previously. I don't know whether that was a sarcastic comment or not, but I thought "Why shouldn't it shock people? The loser has to learn to have better reaction". And so it began.


The hardest part was coming up with a safe method of delivering the shock. First question of how to generate it - the (store-bought) lightning reaction game that I played had plastic-looking controllers and it seemed like the shock was made through a static electricity capacitor (which is why it made the annoying noise, running a rubber belt or something?) that was discharged to a controller. I am not sure whether this is right, but it seems so. In either case, I did not have the schematics or supplies to do a static shock, so I resorted to my usual 'pulsed transformer' approach (used in the Sphere of Power and others). What this implied is that each controller would have two separated metal plates, which a player would hold in his hand and through which the shock would be delivered.

The shock would have to be directed electronically by the BS2 from a single transformer to one of the two controllers. Also I wanted to add an anti-cheating feature that would check for conductivity between the two metal plates (using a Darlington pair for high gain) continuously, so if one person let go of the controller mid-game or was wearing rubber gloves or something, the game would not continue and the other player would not receive a shock. As a result there were competing schemes: on the one hand, a high-voltage spike load would need to be delivered to two plates, and on the other hand a very sensitive high-gain transistor connected to the sensitive BS2 stamp would need to check the plates for conductivity. These are fairly easy to implement on their own but combining the two took some thinking (as I did not want to destroy the BS2 with a high-voltage spike, and did not want to use hackish methods like separate plates for conductivity/shock or pressure sensors for holding, etc).

Transistors and other semiconductors would easily pass the spike through (even diodes), so the only feasible approach would be a physical separation of the sensor and shock circuits by using relays. The sensors would be on by default, then when a player loses the relays would take the BS2 out of the circuit and deliver the shock to one controller.

The relays however introduced another problem: they needed 12V to control reliably, and the BS2 uses a 9V battery. I found a few MOSFETs and thought they would be great for this, but it turned out that they were power mosfets, meaning the voltage to control them would have to be also at least 12V. After a bunch of trial and error, I decided on using transistors. The transistor types AND the way they are hooked up (positive/negative to relay) does matter. See circuit diagram below.



The diagram is available online here! It does not follow any known conventions, but with enough effort and imagination you can faithfully recreate the original Lightning Reaction using the information in that diagram.


The code is also now available online: lightning_reaction.bs2. It is written in BASIC and even has comments so is pretty self-explanatory.


Testing with some friends gave overall positive results. If anything people seem intrigued by the idea and it is enlightening to see the psychological effect this game has on large groups. Immediately some people make a point of their willingness to play while others shy away but eventually 'give it a try', and some others consider it entirely silly and unnecessary.


The only remaining photo of the original Lightning Reaction. It was housed in an old computer power supply and had wooden controllers for each player (not shown) connected to the wires protruding out of the power supply.