This project uses four A101 Dekatron tubes to animate the glow on those tubes in a variety of patterns. Driven by a PIC F16F628A, the animations can give the appearance of the glow moving from one tube to another. 1 of 5 animations can be chosen at any time; an infinite variety of animations are possible based on your code.

Supplies

Step 1: Background

These Dekatrons have 30 pins on which a glow can appear. If the voltage on either adjacent pin is made lower than the one the glow is on, the glow will move to that pin. By manipulating the voltage on the pins, the glow can be moved clockwise or counterclockwise. As there are only 3 types of pins (Cathodes, Guide pins 1, Guide pins 2), this means that there are only 6 glow movements possible. The graphic below shows several pins on a A101 Dekatron, and the 6 possible movements:

Step 2: The Six Movements

The speed of the movements depend on how quickly the voltage on the adjacent pin changes, and if the movement is fast enough, the movement will not be visible until the glow has reached its’ final destination. This allows for the appearance of the glow jumping between non-adjacent pins. By combining slower (visible) and faster (not visible) movements, a variety of motion patterns can be produced.

(To learn more about Dekatrons, see https://threeneurons.wordpress.com/dekatron-stuff/, which is a wealth of information on using Dekatron tubes. Acknowledgment for some of the circuity used in this project goes to M. Moorrees, the author of that site).

Step 3: Coding

I used Great Cow Basic; my code is heavily commented to make it easy to understand. I wrote 12 subroutines to control the glow for each tube; 6 for the visible moves & 6 for the non-visible fast moves. Since each of the four tubes had to be addressed independently, a total of 48 short subroutines were required to make this work. To make coding simpler, the name of each subroutine indicates how it moves the glow:

Step 4: Subroutine Naming

Step 5: Creating an Animation

The order in which you call the subroutines for each “animation” will dictate the final pattern. When creating an animation in code, it is very helpful to refer to a visual template for each tube, such as the one below, where each pin can be individually identified. The 10 cathodes (blue) and 20 guides (green) are arbitrarily numbered for ease in planning. This is not a standard method for identifying each pin, but worked for me. Using this scheme, a visible move from the 12 o’clock position (“K0”) to the pin just short of the 6 o’clock position (“4.2”) would require 14 visible moves:

Step 6: Example Animation

To accomplish this visible move on tube B, you would call these 3 subroutines 4 times in a row:

BVCG1

BVG12

BVG2C

and then call these 2 subroutines to complete it:

BVCG1

BVG12

Step 7: Interrupts

Interrupts were utilized so that when any of the 5 animation buttons are pressed, the current animation is terminated and the new one begins. Note in the schematic that any animation key press triggers an interrupt on RB6, while simultaneously signaling the PIC which animation to use.