neon otis elevator 'touch tubes'

[Joe Zatarski]

So I found an elevator control panel in the garbage. They were replacing a broken one in the dorm next to mine. It appears to have 425A5 'touch tube' trigger tubes instead of mechanical switches. I saw an old thread here about them which had a bit of info. I think you need to connect a 150vac supply between ground and the cathode, then 135vdc across the anode and cathode to use them as a touch button. There needs to be some resistance in series with the tube of course, and the 135vdc needs to be isolated from the ac. Also, I think the trigger input needs to be tied to the cathode somehow.

I still have all the wiring in the panel as it was when I found it. There are 12 floors and a basement, so I'm thinking the buttons can represent the hour of a clock as well as an am/pm light. Furthermore, for setting the time, the tubes can still be used as buttons to type in the time.

I'd appreciate if I can get some tips on driving circuitry and supplies since these are cold cathode neon tubes, something I have never dealt with before.

[Joe Zatarski]

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/s720x720/10698438_610527725718483_574889276774171791_n.jpg?oh=19a589987217d977b1bd6405a114aa2a&oe=54BBBAE2&__gda__=1421665936_039f165285dbc97c5c6f11a9c75d96fe

[Tom Nolan]

Here is the Otis document that has the info I've based my work on. Also,
the 1C21 specs and a newspaper article. These panels ended up as scrap
because of the ionizing source added to lower the trigger voltage.

Tim Lang has been my supplier of tubes and info. If you search for his
posts on this list you will probably find more info.

Cheers,
Tom

On 10/20/2014 11:47 AM, Joe Zatarski wrote:
> https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/s720x720/10698438_610527725718483_574889276774171791_n.jpg?oh=19a589987217d977b1bd6405a114aa2a&oe=54BBBAE2&__gda__=1421665936_039f165285dbc97c5c6f11a9c75d96fe
>

[Joe Zatarski]

thanks, I had the Otis document, but no datasheet for these tubes. I don't believe they are 1C21, but maybe they are close enough? I think my tubes say 2040 on them. Also, that article seems to be something current (2008) whereas this elevator panel is from the 60's or 70's at the latest I think. Perhaps you meant a different article?

[Instrument Resources of America]

Tube Lore lists 2040 in the RCA section as A.K.A. 1C21.    Ira.

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[Joe Zatarski]

Thanks for the clarification.

[Dekatron42]

Here is a photo of a tube marked 2040 on the glass and 425A5 on the base http://www.radiomuseum.org/tubes/tube_2040.html , I can't vote for its authenticity but I have both types but not one with both markings.

I have also scraped away the black paint from 1C21s and they have an identical construction inside and work just as well as the others being touch sensitive. I read a few old patents where they mentioned that the black paint was there just there to make them less light and touch sensitive, the other difference I read about was that the ones used in touch buttons were selected for their voltage, which is how some are marked - the last digit in 425A5 marks the voltage 2 = 72V, 5= 75V on the tubes I own.

You can read more here as they have been discussed earlier: https://groups.google.com/forum/#!msg/neonixie-l/Ygr3IqWcVDQ/2fCV8ANU5XcJ

/Martin

[Joe Zatarski]

I guess now what I would like to know are some example circuits for power supplies maybe? I guess I need 135VDC, and it needs to be isolated from the mains because it'll also have 150VAC on it relative to earth ground. Easiest to do is get a transformer (if I can find the right voltage output) but how about regulation? Is a properly sized zener diode good enough?

[Joe Zatarski]

all my tubes have 2040 printed on them, all of them have a TD71 sticker, and two say 425A5 on a sticker.

[Dekatron42]

I think that the best thing you can do is to ask the company who replaced it if they can help you with any schematics, otherwise you will have to draw one yourself from what you have left of the elevator panel and we can take it from there, then you will know what voltages you need and you can do some experiments more easily.

/Martin

[John Rehwinkel]

I think that the best thing you can do is to ask the company who replaced it if they can help you with any schematics, otherwise you will have to draw one yourself from what you have left of the elevator panel and we can take it from there, then you will know what voltages you need and you can do some experiments more easily.

There are some example circuits in the docs.

I uploaded a few here:

http://www.vitriol.com/images/tech/otis/

- John

[Joe Zatarski]

I will draw up a schematic of what I have in the panel now. I think it'll probably be similar to what the otis docs show: resistor connected in series with the tube, trigger and cathode tied together, and connections for B+ and 'B.O.' (B.O. being the reference line for B+, which also happens to NOT be at the same potential as ground, due to the AC supply tied to it). There seems to be a cap, probably in parallel with something, but I'll take a look.

[Joe Zatarski]

Attached is the schematic in PDF form. All lines except one seem to be common between all the tubes. Based on my guess of 135VDC tube supply, I think I was right. Tube drops about 72V when on, leaving 63V to be dropped by the total series resistance, 3600 ohms. 63V/3600ohm = 17.5mA. This is below the maximum rating of 25mA according to the 1C21 datasheet. It then looks like an AC supply to the grid would be required to cause the capacitive coupling that allows the tube to work as a touch trigger. I'm not too sure how to figure out this voltage.

[Tidak Ada]

Is it clear to you all that this tube has a transparent Sn-coating as the sensitive electrode?

Rough handling of the tube surface can destroy it due to disconnection of that coating.

 

eric

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From: neoni...@googlegroups.com [mailto:neoni...@googlegroups.com] On Behalf Of Joe Zatarski
Sent: dinsdag 28 oktober 2014 20:46
To: neoni...@googlegroups.com
Subject: [neonixie-l] Re: neon otis elevator 'touch tubes'

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[Joe Zatarski]

I was not aware of any coating on the tube, and I don't think there's any connection to the outside of the tube, though I could be wrong. The Otis docs state that the tubes work on capacitive coupling, through the tubes envelope. I do not believe any coating on the tube acts as an electrode.

[Tidak Ada]

I am sure! Try it with an Ohm meter. The top is coated and acts as a electrode.  It stands anywhere in the datasheets. I have that tube for years in my collection.

 

eric

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From: neoni...@googlegroups.com [mailto:neoni...@googlegroups.com] On Behalf Of Joe Zatarski

Sent: dinsdag 28 oktober 2014 22:48
To: neoni...@googlegroups.com
Subject: Re: [neonixie-l] Re: neon otis elevator 'touch tubes'

To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/0ec3b5bc-57d2-4e98-b964-73c584c567ac%40googlegroups.com.

[Joe Zatarski]

You are right. I think it just acts as a plate in a capacitor, working to increase the surface area for maximum capacitive coupling through the tube envelope.

[Joe Zatarski]

I tried it out. It's running off of 200VDC from inside a TV with some extra resistance in between. Using 200V - 72V (the rating of my tubes) I get 128V, and I have the original 3600ohms plus another 3500 in series, giving 7100 ohms. All that results in about 18mA of current through the tube. I even get a bit of touch sensitivity when the TV is just starting up, due to AC bleeding through past the regulators I guess. Otherwise, I can tie the trigger input to the 200V (which has that 1.5Mohm resistor in series) and start it that way.

[Joe Zatarski]

I keep on accidentally saying these tubes are 72V, everytime I say that, change it to 71V...