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I know there were older posts about lighting up old vacuum tubes but I would also like to turn them on and off. I am a complete newbie with no real electronic experience here so please bear with me.

I bought an old cabinet full of brand new but very old tubes that I would like to use/light up as decorative items. Some gave great information on how to light them up, thanks so much, but I would also like to program the lights to go on/off in an interesting way.

I know Amazon sells simple kits that you can create these kinds of things (at least I think they would.) But also what would you all recommend if this was my goal with these tubes? Again complete electrical newbie but very much appreciate any tips, tricks or insights on this project.

Here is a possible Amazon product that I might be able to use.

MarkU
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Lizabeth D
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  • Q1: Please provide a list of the type numbers on the sides of the vacuum tubess eg "ECC83", "EL81" etc. || Q2: When you say "light up" do you mean to illuminate the filamanets = make them low like rather dim light bulbs, or something else ? – Russell McMahon Mar 01 '20 at 02:06
  • Since I have many different types and sizes of tubes I did not list the model numbers. I know that the first number pertains to the voltage so I will keep that in mind here. My minimal goal would be to illuminate the filaments of the tubes with a power source and an on/off switch. But what I would really like to do is be able to adjust how long each tubes filament fades on to off or choose to leave them just on/off. – Lizabeth D Mar 01 '20 at 02:17
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    @LizabethD I'd rather see you donate (sell) your vacuum tubes to a radio club, somewhere. These are valuable for restoration work. Instead, you should look for something like [these](https://en.wikipedia.org/wiki/LED_filament#/media/File:LED_filament_lamp.png). You can either buy the bulbs, crack them open and extract the LED filaments or else you can buy the filaments directly without the bulbs (harder to find that way, though.) Those filaments are often in the range of 70 VDC operation, but you can place them in any number of creative situations (including various glass ornaments.) – jonk Mar 01 '20 at 05:30
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    Tubes filaments don't turn on and off when operating. If you make them blink, then you are making them do something unrealistic. Also, they are not made to quickly light up. You will have to "blink" them very slowly - a minimum of several seconds on and off. – JRE Mar 01 '20 at 10:17
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    I second the suggestion from @jonk to do something useful with the tubes. There are (private) museums and collectors who could make good use of your tubes to keep old equipment running with original parts. – JRE Mar 01 '20 at 10:19
  • @LizabethD You really should `list some example tube numbers. Your statement of what you know about voltages is in error. If you want useful assistance it is usually a good idea to help people to help you. – Russell McMahon Mar 01 '20 at 12:01
  • Most tubes aren't that valuable, some are very valuable - and a few are still made! So post numbers and do what you want with the common ones. Yes the first character often tells you the voltage ( 5 or G = 5V, 6 or E = 6.3V) but... 12AT7 and friends can be run off either 6 or 12V according to how you connect them. –  Mar 01 '20 at 12:49
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    Since the tubes that you got are still supposedly in their original packaging you may want to contact https://www.tubedepot.com/t/tubes. You can browse that page to get an idea of what some types of tubes can bring for prices in the market place. They may very well be interested in your stash of tubes and pay you well for them anticipating that they can make a hansom profit. Note that TubeDepot also sells through DigiKey. – Michael Karas Mar 01 '20 at 13:13

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The filaments in electron tubes have a long time constant. This means that when you apply the power so current flows it can take many seconds for the filament to reach its full glowing hot temperature. This means that any "interesting pattern" that you may have anticipated will have a very slow rate. I suspect that your thinking may have been based somewhat on what you have seen with LEDs that can switch on and off quite fast in comparison.

Switching the filament on a electron tube on and off in a repetitive manner can greatly shorten its life span due to the thermal cycling that the tube will experience.

To deal with the actual switching you need to find the voltage rating and current at that voltage that the filament operates at. A cold filament will draw a lot of current until it heats up over the course of seconds. You will need to ensure that any power source and switching circuitry that you use is fully able to deal with this inrush current.

Michael Karas
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It depends to some extent on the tube PN, but few indirectly-heated vacuum tubes put out enough light to be visible at all under even marginal ambient light conditions. The now-common image in the public mind of a vacuum tube glowing about as bright as a 4W nightlight bulb is pure fantasy: what you see in so many photos of tubes these days is the result of photographic effects, and doesn't reflect reality. To do what you want to do, you'll have to do something like what others have mentioned, e.g. hide a bright, diffused LED under the base of the tubes.

Gary R. Van Sickle
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The tube filament would normally be supplied AC, but DC will work fine also.

The parts kit that you referenced isn't that useful IMO. Maybe somewhat useful for learning electronics, but not that useful for this project.

You need a transistor switch for each tube. A MOSFET is a good choice. It needs to have a low gate threshold, like the one in the schematic.

The filaments draw a lot of current, you will need a hefty power supply if you are powering more than a few tubes. You need to research the tubes to determine the filament voltage for each. 6.3V is common for tubes, but not for modern electronics. 5V is common for modern electronics, you might see if 5V will light the tube satisfactorily. Otherwise, you will need a adjustable power supply that can be set to 6.3V or whatever. If you have more than one type of tube filament voltage, you will need multiple power supplies.

If you want to control more tubes than the quantity of GPIOs on your MCU, you will need a DIO expander.

All of this is fairly simple, but will still be challenging for a beginner.

Get some tube sockets, you don't want to solder to the tubes, they will burn out eventually and need to be replaced.

Cycling the tube filaments will reduce the life somewhat. Maybe someone else can quantify it.

schematic

simulate this circuit – Schematic created using CircuitLab

Mattman944
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  • It would be a good idea to ramp the current up and down - probably an RC on FET gate with slowly increasing PWM mark space ratio. Filaments could be heated to sub visible at a slowish rate and greatly reduce inrush. – Russell McMahon Mar 02 '20 at 13:29
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There are some commercial products that light vacuum tubes (particularly those that don't have a Bakelite portion at the bottom) from below with LEDs, especially blue ones. A bit jarring for the ancient EEs who remember a blue glow as a symptom of something very wrong in the tube.

The actual normal dull red filament glow of a receiving tube such as the once common 12AU7 or 12AX7 is pretty underwhelming, in my opinion. However, if you want to try it:

Here is a typical datasheet. For 12V operation you could use a 12V power supply. The filament current of this particular tube is 150mA between pins 4 and 5. DC will work as well as AC for making it glow.

You could use a simple Ardunio in combination with some logic-level power MOSFETs to control a number of filaments. Suppose you wanted to control 8 on at once, which is 1.2A you could use a wall-wart switching supply with perhaps 1.5A capacity, and MOSFET such as the NTD4815N, which can be easily driven by the Arduino directly.

Spehro Pefhany
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