Here is the schematic diagram
and here is the printed circuit board
The Resistor Clue is a small (1.5 inch x 2 inch) circuit board containing 4 LEDs, 2 wires, and a lot of resistors. If you connect the wires up to a battery then all 4 LEDs light up (any battery should work - AAA, D cell, car battery, cellphone battery, computer battery, etc).
Trace the path of the circuit and create a circuit diagram. Each of the LED's is part of a separate circuit. The separate circuits are conntected to each other only at the ends, where the battery wires are connected.
Each of the 4 circuits consists of an LED connected to the battery through a number of groups of resistors. Each group of resistors is between 1 and 3 resistors connected in parallel. Take a look at the circuit diagram and this will be much clearer.
In the solution each group of resistors represents one letter of a word, and each circuit (each LED) represents one word. The equivalent resistance of each group of resistors is a value between 1 and 26 ohms. This is translated as A=1, B=2, etc. You can find the equivalent resistance of each group of resistors either by measuring with a voltmeter or with the formulae:
Note that these formulas, as well as the key to the resistor color coding system, are found in the DRUID gadget.
The resistor values corresponding to part numbers follows.
The solution is: "code is chrome sculpture"
| Character | Value | Equivalent Resistance | Formula | ||||
| c | 3 | r= | 3.00 | = | 3.0 | ||
| o | 15 | r= | 15.00 | = | 15.0 | ||
| d | 4 | r= | 4.04 | = | 1 / ((1/68.0) + (1/4.3)) | ||
| e | 5 | r= | 5.00 | = | 1 / ((1/15.0) + (1/7.5)) | ||
| i | 9 | r= | 9.01 | = | 1 / ((1/91.0) + (1/10.0)) | ||
| s | 19 | r= | 19.03 | = | 1 / ((1/100.0) + (1/47.0) + (1/47.0)) | ||
| c | 3 | r= | 3.00 | = | 3.0 | ||
| h | 8 | r= | 8.00 | = | 1 / ((1/330.0) + (1/8.2)) | ||
| r | 18 | r= | 18.01 | = | 1 / ((1/100.0) + (1/82.0) + (1/30.0)) | ||
| o | 15 | r= | 15.00 | = | 15.0 | ||
| m | 13 | r= | 13.00 | = | 1 / ((1/39.0) + (1/39.0) + (1/39.0)) | ||
| e | 5 | r= | 5.00 | = | 1 / ((1/15.0) + (1/7.5)) | ||
| s | 19 | r= | 19.03 | = | 1 / ((1/100.0) + (1/47.0) + (1/47.0)) | ||
| c | 3 | r= | 3.00 | = | 3.0 | ||
| u | 21 | r= | 21.00 | = | 1 / ((1/91.0) + (1/91.0) + (1/39.0)) | ||
| l | 12 | r= | 12.00 | = | 12.0 | ||
| p | 16 | r= | 16.01 | = | 1 / ((1/51.0) + (1/51.0) + (1/43.0)) | ||
| t | 20 | r= | 20.04 | = | 1 / ((1/51.0) + (1/33.0)) | ||
| u | 21 | r= | 21.00 | = | 1 / ((1/91.0) + (1/91.0) + (1/39.0)) | ||
| r | 18 | r= | 18.01 | = | 1 / ((1/100.0) + (1/82.0) + (1/30.0)) | ||
| e | 5 | r= | 5.00 | = | 1 / ((1/15.0) + (1/7.5)) | ||
I wrote a resistor calculator program to help create this puzzle. Type in any number (ideally in the 1..100 range) and it will calculate which resistors you can combine in parallel to make up that resistance value. Alternatively enter some text and it will figure out the resistors to use for each letter.
This is a cgi program written in C and the sourcecode is:
The parts to make the resistor clue cost us about $3.30 per clue, or $4 per team (we made extras for backup). You can see the parts list with suppliers and costs here
.Click here for more info on the design of this and other Justice Unlimited circuit boards
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This file Copyright (C) 2004 by Nathan (Acorn) Pooley
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