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Method of generating 170 VDC to drive nixie tubes

by warfreak131
Tags: drive, generating, method, nixie, tubes
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warfreak131
#1
Mar9-12, 12:11 AM
P: 181
In order to operate, nixie tubes need 170 VDC. I know that the mains voltage is 120 VAC-RMS. So if you account for the RMS value, 120*1.414 is nearly exactly 170 V. So would it be possible to make a full wave rectifier?

I decided to simulate the circuit in spice. If I use a 500 uF capacitor and a 1M bleeder resistor, I get a constant line at 170 VDC. The ripple is ~0 V.

My only concern is the stability of the components at such a high voltage. For example, I know diodes have breakdown voltage which apply to reverse current flow, but there may be other factors I'm not thinking of. And I'd also have to find capacitors capable of handing 170 V, although I dont think finding those should be hard.
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turbo
#2
Mar9-12, 06:08 AM
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Why not go back a bit and research the schematics of devices that used nixies as display elements? A lot of people have tried to "start over" and build sweet-sounding guitar tube amplifiers, when all they would have to have done is to go back to Fender schematics and tweak those circuits. That's what Marshall did. Go back to the Fender tweed bassman circuits and build from there. Just a suggestion, because nixies are not used these days, and there might be easy work-arounds in earlier applications.
dlgoff
#3
Mar9-12, 09:44 AM
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Quote Quote by warfreak131 View Post
... but there may be other factors I'm not thinking of.
I would be concerned about your safety. Think about using a switching power supply powered by a low voltage UL approved "wall wort".

Here's a simple 555 circuit kit which uses 9vdc from http://www.ledsales.com.au/kits/nixie_supply.pdf

Attached Thumbnails
switchmode.jpg  

warfreak131
#4
Mar9-12, 12:28 PM
P: 181
Method of generating 170 VDC to drive nixie tubes

i have never worked with anything greater than 24 V, but I would never work with high voltages unless I wear at LEAST class 00 electrical gloves (rated up to 500 V)
vk6kro
#5
Mar9-12, 08:03 PM
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Gloves are not the real answer to this.

The best solution is to never connect anything to the mains unless you can fully enclose the resultant system.

You can't depend on the neutral of the mains always being the neutral if the device is shifted.

Although we have all done it, there should never be exposed conductors with mains voltages (or any other high voltages) on them, even when testing the device.

Isolation transformers are relatively rare and expensive.
An alternative is to use two transformers back to back.
So, if you found a cheap source of identical 120 volt to 24 volt AC transformers you could join the two 24 volt windings together (ie in parallel).
Connect one primary to the mains and take 120 volts, isolated, out of the other primary.
Wall-warts (or plug packs) often have AC outputs and sell cheaply if the device they powered is no longer working.
You can develop low voltages for control circuitry from the low voltage ouput of the first transformer.

You still have to be very careful with the high voltage produced, but at least you can ground one side of it safely.

Some cheap, early TV sets had "live chassis" construction. These could have the chassis randomly connected to one side of the mains.
I attached a crocodile clip from an oscilloscope ground to the chassis of one of these TV sets, not expecting it to be live.
There was a loud bang and the end of the crocodile clip vanished. The ground must have been good, because I was holding the clip and didn't feel a thing.
NascentOxygen
#6
Mar9-12, 10:21 PM
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Quote Quote by warfreak131 View Post
i have never worked with anything greater than 24 V, but I would never work with high voltages unless I wear at LEAST class 00 electrical gloves (rated up to 500 V)
You don't work on high voltage things while they are powered! Even with the mains switched off and the cord unplugged you still can't trust a high voltage circuit. Electrolytics need to be safely shorted because they can store a lethal voltage.
warfreak131
#7
Mar10-12, 12:37 PM
P: 181
Thank you for the safety tips and your concern. I should also mention that I won't be the one doing the work, I am simply pitching the idea. I know a professional electrical engineer who has been in the field for over 40 years. Anything I pass by him would scrutinized for safety.

I may have misled you with this post. I didn't intend on making you think I was doing the work.
NascentOxygen
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Mar10-12, 10:08 PM
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warfreak131, you seem to have not indicated what you will be using the Nixies for. Is this just a 10 min demo on the benchtop, or for a long-term application? If you want the power supply to last for the expected life of the Nixies (I think that's about 200 years ), then the supply will need to be robust and over-engineered.

Does the tube itself emit a soft pop when the digit changes, or is my recall that of the keyboard? As a 1st year student, I availed myself of the physics lab's calculator to process my lab results, and while it was computing the answers that Nixie display seemed to be alive!!
dlgoff
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Mar11-12, 12:12 AM
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Quote Quote by NascentOxygen View Post
As a 1st year student, I availed myself of the physics lab's calculator to process my lab results, and while it was computing the answers that Nixie display seemed to be alive!!
Did it talk to you? The Sixteen-segment ones can.



NascentOxygen
#10
Mar12-12, 02:01 AM
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Quote Quote by dlgoff View Post
Did it talk to you?
I was besotted and beguiled by Nixie's elegance. The glow of her digits dimmed as they danced back and forth in delicate feints before brightening unerringly on each correct answer. For sheer captivating artistry, the Nixie display has seen no rival. I was touched indelibly, the warmth of her true 3D nature remains with me to this day.


Your animation fails to capture the 3D effect as the Nixie digits change.


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