Bertie
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8085 page

8085 page

Fault Finding

Fault Finding

The idea for �Bertie the Beetle� began when I was in my �teens and I wanted to create an electronic sideshow for a local Church Fete. Back in the dark ages of my youth, digital IC�s were a little known phenomena, and in the end I had to revert to the very non-electronic way of adjusting the next winning number BEFORE the next customer came along for a try. As the years went by, one day I decided to have a go and make a �real� Bertie Beetle, just how it should have been all those years ago.

So what was the idea then? Simple but effective. Make an appealing shape on the baseboard, with lots of colours and flashing lights. I chose the beetle, gave it SIX legs, a head with eyes, complete with bulbs-in-ping-pong-balls as antenna! The �customer� simply has the decision of what leg to press (thus operating a switch in the process), having a 1-in-6 chance of choosing the winning one. In the end I went for a pseudo-random style  list of winning numbers (in the prom) which the processor could choose from. If the �wrong� leg was chosen, a musical scale descends through an octave with the display of the �correct� leg on a large LED 7 segment display. If however, the correct leg is chosen, a large WIN light flashes before a simple tune is played amidst flashes of the table tennis balls!(antenna). Amazingly popular with both small children and know-it-all teenagers (who have alledgedly worked out the routine) alike. The first time I used it, at a mere 5p per go, it raised over £32 (UK Pounds)

Bertie Beetle program listing 1 (basic tune) without look-up table (Z80 code)

Bertie Beetle program listing 2 (Jingle Bells tune) without look-up table  (Z80 code)

THE CIRCUIT

In keeping with several other of the more basic circuits on this site, �Bertie Beetle� uses the �digital clock� processor schematic as it�s core. In order to operate the lights and the music generator another piece of circuitry will be needed - using a few �cunning� techniques to keep the component count down to an absolute minimum.This way we can operate any one or more of the peripheral devices by simply sending a code down the single 8 bit wide data bus!

WIN lamp

10h

Octave gen.

20-27h

Antenna

40h

7 seg display

00-09h

   

Thus by sending any combination of these values to the decoder it is possible to turn off and on lights and sounds simultaneously

The LOOK-UP table of winning numbers is created in the EPROM from locations 0500h to 057Fh using a random selection of numbers ranging from F9h to FEh. Mine started off like the following, but you can make up your own �random list� as you like:

0500h

FEh

0501h

FAh

0502h

FBh

0503h

FDh

0504h

FCh

0505h

F9h

0506h

FEh

0507h

FCh

thru to:

 

057Fh

FDh

Data Sheets

Data Sheets

EEprom Programmer

THE MUSIC

A few quick words about the 8x  note generators. To keep the simplicity, I decided to use a terribly elementary concept of creating the whole octave around a bank of  8x schmitt trigger inverters in a 74LS240 package, operated by a set of 1N4148 diodes. Obviously these all have to be tuned in order to play the music and contrary to popular belief, the simple oscillators have managed to keep tolerably close to the real notes over the years without re-adjustment. Enlist the help of a trained musical ear if in doubt! Note that the the reset sequence deliberately runs up the scale of all 8x notes, which quickly shows if any of the notes have drifted to any degree(and thus can be used for �tuning�).

Programmer

Video Information

VIDEO info

Peripheral Circuitry

Peripheral circuitry

To the right we have a single note from the bank of eight. Observe that the outputs of all the generators are connected via diodes into the VN10KM  FET.

Picture
Video

In conjunction with the music generator circuit above, here is the remainder of the simple game interface

Central Heating and Z280's

Z280 and  Central Heating  Controllers

Concluding Ideas

Concluding ideas

Links

Links

http://www.hampshire-shops.co.uk