Russian A-201 Polyatron with carry and set/reset interface - counting in loops!

[Dekatron42]

Hi All,

 

Now I have made simple design that will take a carry signal from any of the Nixie cathodes and then make a pulse long enough for the set/reset stage.

 

There are a few added voltages to this design, one +250V for the set/reset signal and one +60V used as a bias for the otherwise negative pulse taken from the Nixie cathode. There is also a diode at this carry signal shorting any positive pulse to ground, the positive pulse from the set/reset stage will otherwise be present on the carry signal if you put the reset/set signal to the same cathode as where the carry signal is taken, possibly destroying the transistor there.

 

I am sure that there are otherways of solving this that might be smarter in many ways, but this is one that works. The circuit is not perfect either as it loads the A-201 Polyatron so that the counting speed will be lowered due to the capacitive and resistive load from the set/reset and carry loads.

 

The reset signal has a minimum length for the circuit to work properly, there are different values stated in different datasheets, ranging from 170uS up to 300uS - this limits the counting speed a lot so high speed division with anything except 10 has a frequency limit of somewhere around 2KHz.

 

You can also see that I have been experimenting how the 22nF capacitors and the 100K resistors on the auxilliary anodes of the A-201 Polyatron should be connected. Now I have the capacitors to the Nixie anode voltage and the resistors are just connected together on one side. The reason for this is that it works a lot better with the set/reste and carry stages loading the circuit.

 

There is still a lot to experiment with for me (and anyone who wasts to use these A-201 Polyatrons in a clock or something similar) regarding guide bias voltages and also which voltages the cathode and screen electrode should have for it to work perfectly.

 

I made three short movies of the circuit in action:

 

http://www.youtube.com/watch?v=NYhHrQ1fwRA - counting 9, 0, 1, 2, 3 in a loop

 

http://www.youtube.com/watch?v=UoeDvLKGq00 - counting 2, 3, 4, 5, 6 in a loop

 

http://www.youtube.com/watch?v=bGUwAzvNxQs - counting 1, 2, 3 in a loop

 

I've also found a bunch of Russian books on Dekatrons, Nixies, VFD's, LCDs, Cold Cathode tubes (trigger tubes) and other interresting stuff relating to counting. I have no webpage nor any FTP to make these available for download but if someone has I can upload them there for anyone to download. I have given these books to some people on the group but not asked if they can host them yet (will do that after this message is finished!).

 

Enjoy!

 

/Martin

[Dekatron42]

Hi All,

 

I've spotted an error in my schematic!

 

Resistor R5 should NOT be connected to the junction of C2, D1 & R9 but instead to the junction of R9,R10 & R14.

 

Sorry for this mistake, I hope that no one has had problems getting their A-201 Polyatrons up and running due to this error.

 

/Martin

[Dekatron42]

Hi All,

 

Here is the new schematic with the correction for the error described above.

 

/martin