Dekatron Experiments

[threeneurons]

Well, those who know me, know that I have attraction to dekatrons. Here's some of my latest tinkering. A long while back I designed a 4000 CMOS base pendulum circuit. It used a 4017 counter, and a 4013 flip-flop. I revisited that circuit, and came up with one that just uses on 4518 dual counter:

In addition to the one chip, and the HV interfacing transistors, there's a clever little piece of what Don Lancaster referred to as "Mickey Mouse logic". The one transistor and its associated components, in the pink field, form an exclusive-OR gate. Half the chip along with XOR ckt, make the guide timing circuit. The other half of the chip is used as the direction flip-flop. Circuits quite nicely. HV supplies, and clock, not shown.

In my test circuit, I decided to run two dekatrons. One master, and one slave. To align the slave tube, I added a reset circuit to K0 (normally used as the NDX). This forces the glow to K0, instantly. Here's that portion of the circuit:

I hooked it such that when QD (pin 14), of the IC went high, the reset was issued. That meant a reset every 10 'flips'.

It worked ... mostly. I noticed something strange. If I used a A101 as a slave, the glow reset to K0, as expected. But using several 6802's and a GC10B, the glow appeared to reset to K9. After some poking around, I decided to check the reset, with the guides (G1 & G2) off. Then, indifferent to tube type, the reset forced to glow to K0. So this new pendulum circuit "backsteps" some tubes from K0 to K9, almost instantly.

Here's a photo of the test circuit, and video of it running:

Video of above circuit.

Enjoy

[Dekatron42]

Nice!

Could it be that you have a timing issue with the guides not being totally "off" when you do the reset?

Or that the reset does not load the cathode enough so that the glow steps to a lower potential, being K9? You can also check what happens if you exchange the guides, then it should step to 1 instead of 9 - unfortunately not telling you what the problem is but it should at least be another way of measuring what's happening. One more thing to try is to add a resistor in the RTN +55V power line as that then changes the balance between K0 and the other guides.

/Martin

[Nick]

Very nice!

I like the discrete XOR gate but its a lot of complexity when you can get a single "tiny logic" XOR gate from Fairchild, Texas or whoever for $0.10 - one SOT-23 (as opposed to 4 diodes, 4 resistors and a transistor) and you're there... :)

Yeah. I saw the odd voltage levels too!

Nick

[threeneurons]

That's actually the case with everything, when you compare old with new electronics. I can go the whole 9-yards (US term) and just use a microcontroller. Oh ... I do, its that damn DoHickie kit ! Modern technology has turned the economics upside down. So, this project is mostly a mental exercise. At least its more stable, than those log amp multiplier circuits they use to make us suffer thru, in lab experiments, back in school !

 

[threeneurons]

Oh, yes, its a timing issue. It works fine with the guides detached. Its just more of a curiosity. Flipping the guide pins does make it switch to K1. I'll have to analyze my circuit timing more closely to discover the actual mechanism details. The reset is issued at the same time as the flip. Ideally this means its at a main cathode, and the guides should be off. But this is a simplistic circuit, where the prior "main" state, now becomes the new "G1" state. To fix it, here, would add complication. If someone wanted to use the pendulum circuit, with the reset on the second dekatron, its just simpler to rotate the tube such that K9 is on top. Its quite consistent.

In a microcontroller circuit, its a non-issue. To have the glow rest at a "main" cathode, the guides need to be off. So, you just turn both bits off, then issue your reset pulse. Also if its used in a microcontroller circuit, Cr is omitted. Recommended minimum pulse duration is 100uS. The reset can be used instead of monitoring the glow position, and waiting for the glow to be at K0 (NDX). 

[threeneurons]

Yeah. I saw the odd voltage levels too!

Oh on those. If you get a regular nixie supply; 170V. Make a divider out off 3 22K resistors, and the two voltages are 57V and 113V, which are just rounded off to 55V and 110V. That's assuming it was dead nuts on 170V to start with. Throw that 170V on a tripler and you get 510V. Again rounded off to 500V. All these voltages can vary quite a bit, and not effect operation.

[Keith Moore]

OMG! That 0A5 arc discharge dekatron spinner is amazing, too! 

I am ignorant as to the ways of you EE masters. But I want to make one now.   Damn you!

[John Rehwinkel]

> Oh on those. If you get a regular nixie supply; 170V. Make a divider out off 3 22K resistors, and the two voltages are 57V and 113V, which are just rounded off to 55V and 110V. That's assuming it was dead nuts on 170V to start with. Throw that 170V on a tripler and you get 510V. Again rounded off to 500V. All these voltages can vary quite a bit, and not effect operation.

But I want to effect operation!

- John

[threeneurons]

On Wednesday, August 17, 2016 at 2:19:55 PM UTC-7, Keith Moore wrote:

OMG! That 0A5 arc discharge dekatron spinner is amazing, too! 

 I built that thing a while back. I uploaded the video, for another forum, discussing arc discharge tubes:

0A5 Video

One of the destructively cool things about this circuit, is how it continuously popped carbon film resistors in the R6 location. There, current pulses greater than 5 amps, would pass thru. A hole would be punched right thru the outer coating of the victimized resistor. I had to replace it with a wirewound, for reliable operation.