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A Dekatron.
Bozó Balázs
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Glow transfer counting tubes, commonly known as dekatrons, are cold-cathode decimal counting devices. Dekatrons pass an ionization glow around a ring of cathodes by sending a single or offset double or triple pulse to intermediate guide electrodes, causing the glow to advance to the next cathode. Though a few dekatrons were manufactured with speeds as fast as 1 MHz, most were used for applications below 100 kHz. Dekatrons double as both counter and display; the count position is viewable through the top of the tube as a glowing dot. This combination of display and computation in a single component was not replicated in a solid state device until the introduction of LED smart displays in the 1970's. Dekatrons come in three basic types: counters, computer counters and selectors. Counters have a single output cathode, which is pulsed once per full rotation. Computer counters have multiple output cathodes, usually four. Selectors have 10 output cathodes. The earliest and most common British and US dekatrons are 4 kHz neon-filled tubes. Faster dekatrons, in the 10-50 kHz range, are usually filled with argon, popular among hobbyists for the distinctive purple glow. Dekatrons rated at 100 kHz appear to be filled with some sort of Penning mixture, which is about 98.5% neon and 1.5% argon. Such a mixture exhibits an improved ionization rate, allowing for higher counting speeds. A small handful of dekatrons operate at 1 MHz, but their gas fill is a mystery. The 1MHz EZ10B has a purple argon-like glow. While most dekatrons are decimal counters, there are also a few base-12 counters, and one binary counter, which operates like a flip-flop. Overview The VTA Model 600 Dekatron Demonstrator is an advanced computerized spinner, designed to test and demonstrate various dekatron-style glow transfer counting tubes by generating multiple eye-catching display patterns within the tube. The GTC (Glow Transfer Computer) unit is built upon a Microchip 16F84A PIC microcontroller which has been programmed to generate a number of different spinning, stepped and pendulum-style patterns by sending controlled pulses to the dekatron's guide pins. The user can select a pattern or set the unit to automatically cycle through available patterns, changing every few seconds. The speed at which the tube spins can also be set by the user. The unit in this auction includes one Sovtek OG-3 argon-filled 3-guide dekatron pre-installed and pre-configured. The Model 600 is capable of driving virtually any octal-base dekatron with only minimal reconfiguration, and the GTC itself is capable of driving most any dekatron of any base type, assuming the user can find a proper socket. The electronic limitations of the GTC prevent it from driving oddball dekatrons with highly unusual voltage profiles, such as the Sovtek OG-8, but it will drive virtually any other two- or three-guide dekatron. Since the GTC uses a 16F84A PIC microcontroller, it is capable of being reprogrammed with a PC and a minimal amount of commonly available programming hardware. We suggest that the user buy their own PIC chip to program on, instead of overwriting the pre-installed chip and consequently erasing the default program. Functions Mode Button: Pressing this button will sequentially select between one of the demonstrator's seven different spinning patterns. The device also has a shuffle mode which will change the displayed pattern once every few seconds. To activate the shuffle mode, press the mode button until you have cycled through all of the patterns, the device will sound a differently-pitched beep when it has reached its last pattern. Fast & Slow Buttons: Holding down these buttons will increase and decrease the counting speed of the displayed pattern. The maximum speed that can be generated by the pattern generator is 3 kHz, though counting speeds in excess of 500 kHz can be achieved by attaching the device to an external clock source. It should be noted that some dekatrons like the OG-4 can only count at speeds of 2 kHz or less. If your demonstrator has an OG-4 tube installed in it, the displayed pattern will become unstable if the device is increased to its maximum counting speed. The minimum counting speed supported by the pattern generator is around 1 Hz. Guide Control Button: This button will switch the unit between two-guide mode, for using with two-guide dekatrons like the OG-4, and three-guide mode, which works with three-guide dekatrons like the OG-3. After pressing the Guide button, the unit will emit two beeps if it has been switched into two-guide mode, and three beeps if it has been switched to three-guide mode. When changing modes, the '3GD' jumper should be placed when using a three-guide tube and removed when using a two-guide tube. If pressed a third time, the Guide button will put the unit into single input pulse mode, for using an external clock source. The unit will beep once when put into single pulse mode. Pressing the Guide button again will switch the unit back into two guide mode. Pressing the Guide button will also force the unit to save the current settings to flash memory. The unit will automatically save its settings after a few minutes of inactivity. External Pulse Interface: The GTC provides an external TTL-level interface, labeled J2, which allows the user to connect the unit to a word generator or other waveform source and perform various speed and 'torture' tests on a given dekatron tube. The external interface will override the onboard pattern generator when in use. To use the external input header, remove the jumper blocks from J2 and connect a clock source. Refer to the diagram below for TTL interface connections. Sound Function: The unit has a small board-mounted speaker that will softly 'click' every time the dekatron completes a full step. As spinning speeds increase, the clicks turn into audible tones, which can produce some unusual effects with certain spinning patterns. The speaker also sounds various status tones for button presses and mode changes. Removing the SND jumper will disable the unit's speaker. Reset Procedure: If the GTC's memory becomes corrupted, the unit can be reset to its factory defaults. To reset the unit, hold down the Guide button while powering up the unit. Once the memory reset is complete, the unit will sound a series of four tones to indicate success. Power Connections For this device to operate, the user must supply a 9-12VDC supply to power the demonstrator's logic circuitry, and a 110VAC supply to power the anode of the dekatron. A common DC 'wall wart' power supply can be bought anywhere for less than $10, or you can use a 9V battery to supply the necessary DC voltage. The AC voltage can be supplied by a wall outlet in the United States and other countries that operate at 110VAC, or by a step-down transformer in countries that operate at 220V. When making the power connections, be sure to observe correct polarity and to connect each power supply to the proper connector on the board, as a reversed connection could destroy the device. The AC line should be connected to the right-most socket at the top of the board, with the positive lead attached to the rightmost pin. The DC supply should be connected to the leftmost socket at the top of the board, with the positive lead attached to the leftmost pin. Refer to the diagram below for proper power supply connections. To prevent accidental destruction of the device when powering it up for the first time, only power up the DC power supply and leave the AC line disconnected. If the DC line has been connected correctly, the power indicator should light up and the buzzer should begin make regular clicking sounds, indicating pulses sent to the still unpowered dekatron. Next, connect power to the AC line only and leave the DC line disconnected. If the AC line has been connected correctly, the dekatron should display a single stationary cathode glow on one of the pins in its counting ring. If both of these tests are successful, than the power supplies are correctly connected. Example Code For those who want to flash their own programs for the device, here is example code that demonstrates how to spin the dekatron tube left or right. The example code is for a PIC 16F84A, which the user can buy from various retailers. The user should purchase a blank 16F84A instead of trying to re-flash the microcontroller already installed in the device, as doing so will permanently erase the built-in software. ; File dekatrondemo.ASM ; Assembly code for PIC16F84 microcontroller ; Spins a two guide dekatron towards G2. ; Guide outputs are RB1, RB2 ; Copyright 2007 Vintage Technology Association. ; ; processor 16f84 ;----------------- Declare variables J equ H'1F' ; loop K equ H'1E' ; loop SPEED equ H'22' ;spin speed ; Code org 0 ;----------------- Setup the ports movlw B'11111000' tris PORTB movlw B'00000010' movwf PORTB movlw B'00000000' tris PORTA movlw B'00000001' movwf PORTA ;----------------- Set the speed movlw D'100' ;how fast to spin movwf SPEED ; ;----------------- Step the guides one position ;----------------- change xpulse to xpuls2 ;----------------- to change direction. mloop: call xpulse ;----------------- Waste time by running loops bloop: movfw SPEED ; w := speed variable movwf J jloop: movwf K kloop: decfsz K,f goto kloop decfsz J,f goto jloop goto mloop ; Go back and step guide again ;----------------- get states of g1 and g2 and spin towards g2 xpulse: btfss PORTB,1 ;G1 zero? goto g2t ;check G2, else check G2 btfss PORTB,2 ;G2 zero? goto g2s ;then turn on G2 bcf PORTB,1 ;G1 and G2 on,turn off G1 goto gend ; and go to the end g2s: bsf PORTB,2 ;G1 on, G2 off,turn on G2 goto gend ; and go to the end g2t: btfss PORTB,2 ;G2 zero? goto g1s ;then turn on G1 bcf PORTB,2 ;G1 off, G2 on,turn off G2 goto gend ; and go to the end g1s: bsf PORTB,1 ;G1 and G2 off,turn on G1 gend: return ;-------------------- get states of g1 and g2 and spin towards g1 xpuls2: btfss PORTB,1 ;G1 zero? goto rg2t ;check G2, else check G2 btfss PORTB,2 ;G2 zero? goto rg2s ;then turn on G2 bcf PORTB,2 ;G1 and G2 on,turn off G2 goto rgend ; and go to the end rg2s: bcf PORTB,1 ;G1 on, G2 off,turn off G1 goto rgend ; and go to the end rg2t: btfss PORTB,2 ;G2 zero? goto rg1s ;then turn on G1 bsf PORTB,1 ;G1 off, G2 on,turn on G1 goto rgend ; and go to the end rg1s: bsf PORTB,2 ;G1 and G2 off,turn on G2 rgend: return
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| [1] Richard Kline: | Dekatron |
| [2] Bengt Sagnell: | The Decatron tube |
| [3] Ronald Dekker: | Dekatron clock project |
| [4] Mike Harrison: | Dekatron counter tubes |
| [5] Dieter Wächter: | EZ10A Dekatron Spinner Project |
| [6]Ronald Dekker: | A E1T Decade Scaler Tube raised from the dead |
| [7]Jogis: | Ziffern- und Zeichenanzeigen - Die E1T |
A dekádszámlálócső.
