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 Post subject: Dekatron spinner circuit and other neon circuits
PostPosted: Nov Tue 12, 2019 3:37 am 
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Location: Warner Robins, GA
I have the following dekatron spinner circuit I built a few years ago which I just found tonight among some of my stuff.

Attachment:
dekatron spinner .png
dekatron spinner .png [ 149.95 KiB | Viewed 871 times ]


Upon powering it up, it worked ok, then as I increased the speed it stopped on one segment and would not advance further no matter what oscillator speed I ran it at.

After a minute or two of being left on in that condition I noticed the circuit had resumed normal operation.

What would cause that?

What I plan on doing is mounting it in a case and power it off the isolation transformer I used for the nixie flower I built which is similar to this only the neons are arranged like a flower.

http://www.bigclive.com/stix.htm

May reverse the transformer though as it puts out 126Vac for a 120Vac input with such a light load.

I'll feed the voltage to the secondary and I'll have the two 115vac primaries as the output provided the voltage isn't too low.

A switch will allow me to turn the dekatron spinner off if so desired.


Last edited by Tube Radio on Nov Fri 29, 2019 4:59 am, edited 1 time in total.

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 Post subject: Re: Dekatron spinner circuit question
PostPosted: Nov Fri 22, 2019 4:42 am 
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Location: Warner Robins, GA
Here's what I did.

I decided to get creative with the voltage dropping.

I used the transformer with the primary connected to the line.

For the nixie flower I put a 139K (three series resistors) resistor in series with the circuit to drop the voltage to 120Vac.

For the dekatron spinner I put a .18uF cap in series with the spinner's power wires and that didn't drop it enough so having no other lower value of capacitor handy I put a resistor of 136K to the common of the isolation transformer secondary after the .18uF cap.

I plan on finding a box to put the spinner in and then will mount that box to the side of the nixie flower box.

I may install a DPDT switch so that I can reverse the direction of the dekatron spinner if so desired.

Oddly enough the max speed of the oscillator is a little lower than it was when I initially built it using my RCA TV iso-tap WP-25A isolation transformer, but measuring it recently I found under the light load it puts out a little more than 120Vac so that may be why. Perhaps lowering the value of the 330K resistor will work. I did adjust the 1 meg max frequency adjust to its highest speed though and the oscillator was still running. When the circuit is right, the oscillator can be set to the point it goes so fast that the neon lamp just stays on and the oscillation stops. What's happening I believe is as the resistance gets lower it brings the voltage up to the voltage the neon fires at such that the cap doesn't need to charge in order for the neon to fire and thusfore the neon stays lit.

What I would like to do is find more interesting neon lamp circuits, build them and run them off the same transformer.

In hindsight I should have put the voltage dropper circuit on the spinner board as that would make it easier to add more neon lamp circuits. I will modify the nixie flower circuit though to add an on/off switch. Each circuit will have its own power switch so I don't have to run them all if I don't want to.

The box the nixie flower is in is a radio Shack project box set so that the open part is vertical so that the nixie flower can be seen from the front.

I will find another box for the spinner, but it needs to be deeper than the nixie flower box. With the boxes vertical like that I can install switches and controls on the top of the boxes. Now I'm not too concerned about exposed switch terminals as I am running this off an isolation transformer. Given the low current the neon circuits require I can run a whole lot of them on the isolation transformer, although I'm not sure there's enough variety of neon circuits to ever draw anywhere near the max current of the transformer plus I wouldn't have the space to put enough circuits.

What other flashing neon lamp circuitry can I build besides the nixie flower?

Here's two circuits from http://www.bristolwatch.com/ele/neon.htm

Image

Image

Neither will need any voltage dropping and can run off the same DC supply and I could possibly put them in the same box.

Now the ring counter if I wanted to add more neons do I just add more neons, 1 meg resistors and .5uF caps as they are in the existing circuit?

Now if other circuits run on 160-170Vdc I can just use one supply to serve as the DC supply for the circuitry.

Now here's some colored neons.

https://www.amazon.com/Colors-Miniature ... B00WQ6ES0O

Would they work in any circuit using a NE-2 and would their life be as long as a NE-2?

Here's a variation of the two neon lamp flasher with speed control.

Image

From http://www.giangrandi.ch/electronics/neon/neon.shtml

For the ring counter I may do the same type of speed control.

I have a breadboard I can use to build both circuits for testing purposes so I can get them tweaked properly before building on perfboard.

Concerning the dekatron oscillator I may remove its connection from the dekatron spinner power supply and power it with a separate diode before the voltage dropper circuit so I get the full available speed of the oscillator. I may also replace the 5 meg pot with a trimpot as I don't see me adjusting the speed often.

I'll at least do the ring counter for sure. Not sure about the two neon flasher.

So that will make a nixie flower, dekatron spinner and neon ring counter so far.

Would like other ideas for flasher circuits only using neons, caps and resistors.


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 Post subject: Re: Dekatron spinner circuit question
PostPosted: Nov Wed 27, 2019 3:49 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Warner Robins, GA
Parts are ordered.

Both the ring counter and lamp flasher will be breadboarded first to see how well they work.

EDIT:

What I plan on doing with the spinner, ring counter and flasher is find a case the same size as the case the flower and power transformer is in only a little deeper so that the dekatron doesn't stick out of the case then mounting the three circuits inside the case with all switches on top.

I'm almost tempted to rig up a transistor, DPDT relay and a Christmas light flasher bulb to control the transistor so that the dekatron will randomly reverse direction, but that would require a low voltage power supply.

EDIT:

The neon flasher has been breadboarded and the modified circuit is as follows.

Attachment:
Neon twin-blinker with speed control.png
Neon twin-blinker with speed control.png [ 5.85 KiB | Viewed 650 times ]




EDIT:

Pretty sure I won't use the neon flasher circuit as is.

I had to modify the ring counter circuit as it simply would not work as is without buying a bunch of neons and checking them until I found 10 with very close specs.

So here's the circuit.

Attachment:
Neon ring counter 1.png
Neon ring counter 1.png [ 26.22 KiB | Viewed 644 times ]


Now if I want to use the twin neon flasher I can do the following. I don't know yet what value the one capacitor will be as that is determined by the fastest speed I want the oscillator to run.

Attachment:
Neon ring counter 2.png
Neon ring counter 2.png [ 26.67 KiB | Viewed 644 times ]


EDIT:

I tested the last circuit, but had I been thinking I wouldn't have had to in order to know it wouldn't work.

With the modified ring counter I have so far been able to get 5 neons going in sequence.

On a whim I decided to substitute one of the 100 white LEDs I got from Electronics Goldmine for a diode and it lit up to a usable brightness.

On the breadboard I only have room for maybe 7 neons. I need to order more neons anyways so I can have more to choose from so I'll order another breadboard as well.

I am marking the neons on one side as it matters which way they are connected as some work one way and others I have to connect in reverse for them to work right.

The plan is to do 10 and because I'll have extra neons I may try more.

I'm tempted to use the LEDs for the diodes, but the white light will mess up the orange look of the neons, although I could mount the white LEDs to the rear of the PC board and cut a hole in the back of the case.

Not sure how I want to lay out the circuitry though. I know the neons will be in a circle and I might just put the rest of the circuitry in a line at the top. If I used the LEDs I could cut holes in the top and have the LEDs sticking through.


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 Post subject: Re: Dekatron spinner circuit and other neon circuits
PostPosted: Dec Thu 05, 2019 6:32 pm 
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Location: Warner Robins, GA
After much tweaking to the circuit I've made it very stable and not near as picky as to the neons I use.

I condensed it down to three neons for the schematic, but in all reality I could use pretty much as many neons as I desired.

I'll do at least 10 neons which was the original plan.

I'm tempted once I get the other neons to try two neons in series. I would then do 20 in a circle and wire them to where the neons are on opposite sides from each other so that I will have two neons going around the circle and not just one.

The 330K series resistor would have to be made lower though.

The 3 meg resistor is to keep the dc voltage below the transistor's maximum as I tried the only other high voltage transistor I had and I couldn't get the circuit right.

The pots are like that because a single 5 meg pot wouldn't cover the full range of frequencies I desired. The 1 meg is there as it keeps the transistor from going bad should I turn both pots to minimum resistance.

Attachment:
Circuit 2.png
Circuit 2.png [ 6.78 KiB | Viewed 568 times ]


EDIT:

I got the circuit working with all 10 neons.

The circuit is quite insensitive to the individual neons.

I found that out when I stuck 10 more in the circuit so that each part has two neons in series. Circuit works great.

Bit concerned about the transistor though.

B+ on the collector at the oscillator's slowest speed is 102Vdc.

The pulse is quite narrow and is -106Vp

2N3019

https://www.onsemi.com/pub/Collateral/2N3019-D.PDF

Think the only reason I'm getting away with it is because of the very short pulse width.

I may look for a better transistor in my stash that can handle at least 200Vdc.



EDIT:

Here's the final circuit only showing three neons, although I could theoretically use as many as I so desired.

When I breadboarded the circuit I could only get the oscillator up to around 60Hz.

Now its maximum is 102Hz.

Attachment:
Neon.png
Neon.png [ 7.77 KiB | Viewed 464 times ]


Here's pictures of the circuit board.

Attachment:
20191210_150451.jpg
20191210_150451.jpg [ 373.06 KiB | Viewed 464 times ]


Attachment:
20191210_150519.jpg
20191210_150519.jpg [ 418.12 KiB | Viewed 464 times ]


I'm very tempted to build another cone of these using 10 neons feeding a ring counter using 6 neons. I would then figure a way to make the oscillator use or trigger off the 60Hz line frequency. I would then have a 1PPS circuit. More 10 and 6 neon circuits could be used for seconds and minutes. For hours I would use a single 12 neon circuit as that would be much easier than a 10 and 2 circuit given I wouldn't need reset circuitry for the 10 circuit when the 10 and 2 circuit reaches 12.

The neons could then be used as the hours minutes and seconds display.

If I did do that I would find some sockets that the neons can just plug into so should I need to replace a neon it would be very easy.

I would also add a DPDT switch and a couple buttons so that I could set the time properly. The switch would disconnect the seconds from the minutes and the hours from the minutes and connect them to the circuitry operated by the buttons. Perhaps the button circuit could derive the necessary pulse from the output of the divide by 10 circuit.

I would use no chips only neons, resistors diodes and caps. That way I only need a single isolation transformer and no low voltage supplies.


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 Post subject: Re: Dekatron spinner circuit and other neon circuits
PostPosted: Dec Fri 27, 2019 11:59 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20688
Location: Warner Robins, GA
Here's the whole thing as far as I have it at the moment.

I just need to find the proper box for the dekatron spinner and I'll be good to go.

Attachment:
20191227_152821.jpg
20191227_152821.jpg [ 165.8 KiB | Viewed 391 times ]


EDIT:

Discovered a problem with the circuit last night.

It doesn't work so good in a totally dark room.

I took my cellphone with its screen set to its lowest brightness and held it near the front of the boxes. The circuit then started working normally.

I then decided to try a flip clock mechanism I pulled from an older clock radio years ago as it uses a neon to light the numbers and the light from the neon got the circuit working properly.

So I'll add a neon to each circuit powered off the secondary of the isolation transformer with the correct series resistor for each neon.

EDIT:

Here's how I did it.

I put a 200K resistor in series with each neon for just under 500uA of current. The neon for the nixie flower has a 1 meg trimpot in series with the 200K resistor so that I can adjust its brightness to what works best so that all the neons randomly flash in a completely dark room. If the neon is too bright they don't all flash right and if it is too dim they all don't flash right.

I put the neons in the center so that each neon gets the same amount of light.

Attachment:
20200102_010848.jpg
20200102_010848.jpg [ 110.03 KiB | Viewed 291 times ]


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