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Objective To turn one side of CSU's Rhodes Tower into a gigantic-scale game of Tetris that can be played from a distance.

Status Initial plans only; won't happen anytime soon.

Intro This was an idea conceived for a 2008 National Engineers Week project for the CSU IEEE branch, but funds were directed elsewhere. It would be rather easy to build a large game of tetris using PLC's (programable logic controllers) but the point here is to do it as cheaply as possible and using mostly analog circuitry (also wirelessly). The tower's main windows are 12 tall and 12 across, for a total of 144 "blocks" or "pixels" for the game. So 144 inexpensively-produced wireless receivers need to be made. To send the signal to each receiver, a main transmitter/controller would be at the location of gameplay. The transmitter sends the signals to all 144 of the receivers which in turn would switch on a light source such as a string of cheap christmas lights hung around the inside of the windows. Receiver The initial brainstorm schematic is shown below. Each receiver circuit is identical except for a RLC tuning circuit or filter. This filter allows a specific receiver to lock onto a single specific frequency which will trigger that particular circuit. The filter's output will be highest when the antenna is picking up it's tuned frequency. The output is then amplified using a BJT transistor, positive-rectified, and fed into a op-amp comparator, which compares it with a predetermined voltage (this voltage can be changed to adjust the 'sensitivity' of the device). The op-amp's output is then connected to the gate of a triac which controls a 120-volt ac output to the string of christmas lights. The dotted line represents a possible connection between the 120v string of christmas lights and the antenna because it should be possible to use the christmas lights as the antenna, and simply isolate the higher voltage from destroying the circuitry by using a capacitor that will block low frequencies (such as 60hz). Since this is mostly low voltage circuitry, with exception of the strings of lights, we will need a DC power source of about 12 volts. Since our circuit isn't very sensitive or power hungry, this can be cheaply done by using a diode rectifier, capacitor filter, and voltage divider to provide 1/10th of the 120v supply for the circuitry. This is seen in the upper area of the schematic, but only drawn as a half-wave rectifier. Transmitter All the transmitter has to do now is transmit each of the 144 carrier frequencies when we want them to turn on each window. To avoid needing 144 individual receivers, this is done by using only one receiver that constantly sweeps through all 144 frequencies, transmitting for the ON blocks and not transmitting for the OFF blocks. To prevent the blocks from just flashing only when it is receiving, a capacitor (Ct in schematic) is used at the comparator's output to hold the circuit high for a certain length of time. This length of time and transmitter sweep speed is determined by gameplay speed. We can assume the shortest durration of a block being on (as the tetris block is falling quickly) is about 0.5 seconds. That is then used to calculate the capacitance inserted at the comparator's output to hold the output high for half a second after it receives it's signal. That also means we need to cram the entire sweep of 144 frequencies into a half second or less: 0.5s/144 = 3.4 ms. Thats 3.4 thousandths of a second that each frequency will be allocated for transmission. The frequencies chosen for this project and the separation distance depends on a few things: 1) The amount of interference is within the range. We don't want blocks turning on by interference. 2) Reasonable specs and cost for the filter components. 3) Low-order filters mean the signal frequencies will need to be more spread out so they don't trigger eachother. The game Tetris itself will need to be controlled by a computer (or a hacked gameboy?) which will feed the pixel/block outputs to the transmitter for translation to 12x12 Rhodes-Tower-blocks. We'll leave this to the software and computer engineers to figure out. The game can most likely be controlled by our favorite controller: Cost The initial goal of this was to keep it under $1000. The receivers would literally be around $1 each: diodes, capacitors, and resistors just a few cents each (some of which we have); triacs and op-amps in the range of 20 cents each. That leaves the string of christmas lights, from which we can tap into the power cord for the circuit's power supply. The cost of the transmitter or game control has not been researched.