Der sinnlose Zähler: a Picaxe powered, Dekatron and Nixie display, do-nothing box


Senior Member
How to marry ancient display technology, namely Dekatrons, Nixies and neon lamps, to a Picaxe?

When I was young, I built several idiot boxes employing neon lamps.
Time to marry modern technology with ancient display technology



Senior Member
I had several pieces of the puzzle lying around:
-a pair of Picaxe 20M, whose limited program length is no match for its I/O
-a pair of Z560 German Nixies and some NOS Soviet 74151 Nixie drivers.
-a pair of Soviet OG4 dekatrons
-time on my hands.

I had already purchased a Dekatron spinner kit from Ebay, and it is fascinating to watch, for a while.
Remembering my youngster days, and how relaxing is to waste time watching neon lamps blink randomly, I decided to build "Der sinnlose Zähler".
Literally, the senseless counter.



Senior Member
The circuit:

The core is a 20M generating random numbers, and then using those numbers to advance or decrease the count.
To assist in the randomness, the AC waveform is sampled via the ADC10 command, and its value is used as a "seed" in the random variable.
The Nixies operate from 170VDC, and the Dekatron require 510VDC. To obtain those voltages, a small 12VDC to 170VDC module provides a safe method to do so.
The 170VDC comes straight from the module, the 510VDC utilizes a voltage tripler, as outlined in the same website.
The easiest way to drive a Nixie is utilize the 74141 IC. It requires a TTL level BCD input, and decodes the 10 segments with a high voltage driver.
The Dekatron requires a two phase drive, similar to stepper motors, for rotation and direction control. The Dekatron also features an"index" pin, really a zero count detector, to synchronize it.
I included some sound effects, which are timed with the Dekatron counting pulses. Simultaneously, the Neon lamps are pulsed.
Although I could have used a single Picaxe to drive both Dekatrons and Nixies, I decided to utilize wo independent devices to enhance the randomness.
Lastly, to increase the entropy, both Picaxes tickle each other via the sync pin.

Schematic supply.png

schematic main.png


Well-known member
Looking at the photo and video this seems like a very simple project, but thinking about it and seeing your other data proves otherwise!

Good stuff. Makes me remember a data panel I had to watch on an offshore drilling rig for 30+ hours at a time. ;)

Useless, but necessary at the same time.


Senior Member
Please find the attached files for the OG4 Dekatron and the Z5600 Nixie.

The Dekatron datasheet is in Russian. But the pinout is as follows:

1- Index (0) cathode
2- no connect
3- Anode
4- Grid 1
5- no connect
6- Grid 2
7- no connect
8- cathodes (1 thru 9)