Scoreboard Last update 20 december 2006

Control box

The function of the control box is to translate the code from the thumbwheels to serial data and after that to cds code.
The box consists of the following parts:
  • Shift register
  • CDS coder
  • Signal/power separation

Control box with thumbwheel switches

A thumbwheel switch is an electrical part to convert the manual imported values to an electrical equivalent, in this case BCD code. Each thumbwheel has 4 wires. Since there are 8 figures in front of the scoreboard (3+3+2), there are 32 wires. So these give a binary zero or one to the 32 inputs of the shift register.

Shift register

In the shift register these 32 parallel bits are converted to serial bits by importing the 32 bits at certain times with the aid of a "parallel load" (PL). This happens in the circuit with 4 x HEF4021. The bits are continuously shifted to the right with the aid of the (T) wire via the inverter. In the flow diagram signal (D) is the data stream and for example there are drawn 5 bits with equal time intervals (10010).

Schematic transmitter

CDS coder

The left HEF4011 together with the HEF4013 form the CDS coder.

  Transmitter flow diagram Signal (1) is formed from the combination of (D) and (2T) in the NAND gate. Signal (2) arises from (D)invert and (T). During the whole 32 bits period output 32 of the HEF4024 is low so that a NAND gate of the right HEF4011 is closed. Because of this one can think of signal (3) built up from (1) and (2). (The right HEF4011 is only way through.) In the HEF4013 signal (3) is divided by 2 and arises the CDS signal (4).
One sees direct the singularity of the cds code:

  • A '1' in the data stream gives a change in the cds code.
  • A '0' in the data stream gives no change.
  • In the average the cds signal is low or high during the same time, this means: no DC contents.
  • In any case there is a change in the cds code at every bit transition of the input signal. This means that the clock is present in the cds signal.
With the aid of the right half of the HEF4011 in the schematic every 32 bits a synchronizing bit is added with a length of two data bits. This sync. bit is needed to distinct the first serial bit.

The frequency of the oscillator (2T) amounts about 10 kiloHertz, so that the clock for the serial data is about 5 kHz. The refreshing frequency of the parallelbits then is about 5000/32= approx. 150 Hertz.

Separation of the signal and the supply

The cross-over filter consists serial capacitor and a coil. The data signal an the supply travel together over a 2-wire connection between control box and scoreboard. The supply is meant for the control box and the data stream just goes the other direction to scoreboard. There is no distorsion if the capacitor has satisfactorily capacitance (abt. 1uF) and the coil enough self-inductance (abt.1uH). The control box consumes not much current, so the coil may have thin wire.

Wiring

wiring Example of wiring of a part of the transmitter print. Eventual transformer wire of 0.3 mm. can be used. The insulation of modern transformerwire melts with a hot soldering iron so that is not necessary to strip.

 

 

 

 

 

 

 

 


Control box, the one with thumb wheel switches.

Control box with push bars

It is possible to replace the thumb wheels by an electronic circuit with push buttons.

Perspective

Control box with push bars. The box contains bars sawed from glass fiber circuit board. In the board there has been sawed 8 fingers: 3 for the first player, 2 for the inning and 3 for the second player.

Push bars Side view
The (springing) fingers are sawed in a glass fiber board of 1 mm. Each finger is provided with two click switches for up an down count. An electronic circuit takes care of the control of the 32 inputs of the HEF4021 ic's.

Schematic push bar

For every element (total 8) in the display there exists a HEF4029, this is an up/down counter. The diodes between the HEF4029 are needed for the carry.
The 10 kHz. oscillator and the 4040 divider is combined with the cds decoder.
The reset switch reads in all zeroes via the PL wire, so that all 4029's are set to zero except the most left HEF4029 is set to BCD 1010, this is decimal "10". This is the first -not used- code. The first 10 codes (0 to 9 incl.) are used for the figures 0 to 9 incl. With the "10" the text: "HBV DE BUN" is displayed.

Bottom view
Parts view of the transmitter with push bars
The characters "HBV DE BUN" at the bottom are not generated in the HEF4029's but but only serve as an aid to determine the right 4029.

Test circuit

With the test circuit a control box can be tested seperated from the main display. For the coil u can use for example a primary winding of a small 220 V. transformer.
When an external sync. connection is used, this must be connected to the Parallel Load in the box.


Output signal of the control box. There are two sync. pulses, one positive and one negative.

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