THIS PROJECT COVERS 7 BUILDING BLOCKS AND MAKES A VERY INTERESTING GAME FOR TWO PLAYERS

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The circuit diagram for the Hangman

This is a HYBRID circuit - meaning it is composed of two different species. We have combined transistors with IC’s to achieve an update of an old game. The complexity of the circuit comes from the repetition of the transistor stages. Due to the number of biasing resistors required it is strongly suggested that you use a PC board. Not only has the layout of the board been carefully designed to make it look symmetrical when completed but it also allows the project to go together so much easier. The boards are printed with an overlay and will fit directly on top of a project box so the appearance looks professional.
Everybody likes re-discovering something they did years ago. Here’s a game we all played at school. Possibly under the name of HANG THE BUTCHER. The game is quite simple. One player thinks of a word and writes down the number of letters in that word in the form of boxes or dashes. The object of the game is for the opponent to suggest letters of the alphabet, and if they are correct, are placed on the dashes in the correct order so that the word gradually appears.
To make the game more interesting, a side issue is introduced which effectively counts the number of incorrect guesses. Each time an incorrect letter is suggested, a systematic framework is created with straight lines in the form of a gallows. A stick man, representing a person being hung, completes the diagram.
The game is concluded when the correct word is created or the stick man is completed, whichever comes first.
This is an electronic version of that game. The stick man and gallows are made with 15 LED’s and each time a TOUCH PLATE is touched, one more section of the cartoon is illuminated.
The last LED’s to be lit are 14 and 15, which represent the feet of the man. When these LED’s are at full brightness, the 8th LED begins to flash, indicating the man is ‘HANGED’.
The game can be played in two ways. The ‘normal’ way involves the secret word and using the hangman to count the incorrect letters. The other suggestion is to take it in turns illuminating the LED’s until the flashing LED is set into oscillation.
The player creating the first sign of continued flashing is the winner.
In either game, you will have lots of fun. Especially in a darkened room where the full effect of the LED’s will be produced.

HOW THE CIRCUIT WORKS

The HANGMAN game consists of 7 main building blocks. These are shown in the block diagram and are identified as follows:

7 BLOCKS

1. 2Hz oscillator with voltage trip.
2. 2KHz multivibrator
3. Voltage doubling
4. Staircase voltage detector
5. 1/4 second de-bounce
6. 1/10th second ‘one shot”
7. Shut down.

The Hangman Block Diagram

When the power is applied, the only building block to come into operation is the 2kHz multivibrator, block 2. It is made up of gates c and d of 1C2 and feeds the push-pull buffer consisting of Q11 and Q12 to charge the 100mfd electrolytic. The oscillator runs at a fairly high frequency and this reduces the size of the coupling capacitor. This building block is called a VOLTAGE DOUBLER and the voltage appearing at the output terminal is very close to double the 9v supply minus the voltage drops across the two diodes. Under no-load conditions this voltage appears at the output as 14v. We call this BOOST and we have labelled it 12v BOOST because it reduces to 12 volts under full-load conditions.
The mechanics of the voltage doubling circuit are very easy to follow. The multivibrator c and d produces a square wave which is fed to the bases of the two complementary transistors. When one transistor turned hard on, the other is full off. For the first cycle, the output gate c is LOW and the BC557 is turned ON. The negative end of the 22u is taken to the negative rail and charges quickly via the top 1N4002 diode to 7.5v.
At the same time the 100u electrolytic is charging to 7.6v via the two diodes. When the multivibrator swings HIGH, the top BC547 transistor turns ON and the BC557 turns off. The negative end of the 22u is now brought to the positive rail and its stored 7.5v will be added to that of the 100u electrolytic to bring the total voltage up to 15.2 volts minus .7v drop across the lower diode. In fact the voltage drop across the diodes have a double effect on reducing the voltage since they are used for each part of the voltage doubling action. They account for nearly 3v drop.
We must also include the collector-emitter voltage drop of each transistor as this reduced the maximum voltage available on the 22u boosting electrolytic. Thus the resulting voltage out of the doubler is considerably less than you would expect. All these diode and transistor voltage drops are constant for any voltage doubler and would obviously be less noticeable when using higher voltages. This arrangement is capable of delivering 15 to 20 milliamps and since it does not have a very good regulation, the voltage under load drops to about 11 or 12 volts. This is just enough to illuminate LED’s 14 and 15 in the staircase circuit.
LED’s 14 and 15 are positioned as the feet of the man being hung and are controlled by transistor Q10. The reason for providing a voltage doubler circuit is two-fold. It introduces a new building block into our “library” and adds interest to the project while providing an economical way of producing the necessary higher voltage rather than using a 12v battery.

Pin out for the CD 4011

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