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These fixtures were made by Otis and used on their Autotronic elevators in the 50s-60s. These fixtures are totally unique from others as they use vacuum tubes as the main component. There were three main cosmetic variants of touch buttons each using the same tube for the electronics.
Square
These could be found on both car panels and call buttons
Circle
These could be found on both car panels and call buttons
Arrows
Found only as calls (for obvious reasons)
Wiring
As for wiring these fixtures, it's a bit more complicated than the majority of my other projects. Since these are vacuum tubes, they require specific voltages and circuits in order to function correctly. These tubes ideally would like 135 v DC and 150 v AC. Those voltages aren't readily available for most people! Luckily for us, 120 v AC is close enough to 150 v AC where we can use it to power these tubes up to use as a display piece! Since that's what my projects are geared towards, this works in our favor!
Wiring video
This video shows you how to connect 120 v AC to the tube base (for call buttons) in order to get them to run as described above. Connecting the 120v to the tube base is very straightforward. I also show how these tubes are supposed to behave on a car panel and some cool things you can do with them. For more info of wiring, see the information listed below.
More Wiring Info for call buttons
When it comes to wiring call buttons, your tube base will have markings on each of the connectors. At LEAST, you should see a C, 3, and 4 pin. Each of these pins represents a connection to the tube itself (there are other components on the tube base as well).
C - Cathode: Live (Two cathodes for intermediate and one for terminal. On an intermediate, the two C pins have to be connected with a wire)
3 or 5 - Anode: Neutral (3 appears on the terminal and both 3 and 5 appear on the intermediate. Both 3 and 5 are connected already)
4 - Grid: Not used in the project but functionality shown in the video.
Car Panel
As stated in my video, the 120 v AC on the car panel won't work the way it does for the call buttons. The main issue is we are not using 150 v AC as the trigger, so the tubes will not activate with the panel on top. The tubes just aren't sensitive enough through the panel to detect the touch using 120v. Therefore, in order to get the car panel to work as intended, we must use the correct voltage which requires a custom power supply.
I have an AC to DC converter board that I can use to produce the 135 v DC needed for the tubes, however, since my source is only 120 v AC, the plate will still not work with the tubes. I used this board to demonstrate how the tubes would behave under more normal conditions and how the grid works with crossfiring the tubes. As I stated in my note for wiring the call buttons, we can use DC on the car panel because it has the 2 W resistors to limit the current to the tubes. If you do have access to 135v DC you can connect up the tubes as shown below
In this image, the following colored boxes mean:
Green: Anode - Positive of DC source, neutral of AC source.
Red: Cathode - Negative of DC source, live of AC source.
Yellow: Grid - This MUST be connected to the cathode to prevent all the tubes from lighting up as demonstrated in my video.
Blue: 2 W resistors. These limit the current to the tubes allowing us to use a DC source.
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