If an RCM 3 isn't available make your own....

[AllSafe]

My siren timer is a vacuum tube timer.
When an element inside the tube heats sufficiently, it opens it's contact in 180 seconds. Once open, I desiged the circuit to reset.

It's a time-delay relay for a tube radio or transmitter, isn't it?

[Robert Gift]

My siren timer is a vacuum tube timer.
When an element inside the tube heats sufficiently, it opens it's contact in 180 seconds. Once open, I desiged the circuit to reset.

It's a time-delay relay for a tube radio or transmitter, isn't it?

I don't know. Looks just like a vacuum tube with a multi-pin base.
Thought it simply a cheap easy timer from the 60s before solid state timing circuits were developed.
It is a time-delay device.

[AllSafe]

My siren timer is a vacuum tube timer.
When an element inside the tube heats sufficiently, it opens it's contact in 180 seconds. Once open, I desiged the circuit to reset.

It's a time-delay relay for a tube radio or transmitter, isn't it?

I don't know. Looks just like a vacuum tube with a multi-pin base.
Thought it simply a cheap easy timer from the 60s before solid state timing circuits were developed.
It is a time-delay device.

Yeah, exactly; it's a time-delay relay, which is used to delay the application of B+ voltage while a tube circuit is being warmed up. It's not a vacuum tube because the relay doesn't sit in a vacuum, but rather an inert gas.

[Robert Gift]

... It's not a vacuum tube because the relay doesn't sit in a vacuum, but rather an inert gas.

Interesting! Thanks.
Why not a vacuum? Would that not be easier than an inert gas?
Did I see Getter in it? Guess not.
To determine gas, I'll have to look at the spark when the contact opens.
I never knew that filaments need be up to temp before B+ was applied.
180 seconds is a LONG time!
What kind of applications?

[hobbeekid]

wooosh! over my head,I could'nt even begin to explain how these timers work let alone build one from scratch. I have ar timers myself and I have no idea how they work inside,never bothered to find out, just somthing to look at.You definitly have skills Eric.

[Robert Gift]

wooosh! over my head,I could'nt even begin to explain how these timers work let alone build one from scratch. I have ar timers myself and I have no idea how they work inside,never bothered to find out, just somthing to look at.You definitly have skills Eric.

Kid, you can figure all of this stuff out! Follow wires and draw up you own schematic (wiring diagram).
This is all electro-mechanical. Nothing solid state.
It's fun.

[jmev]

Most of these delay tubes were a simple heater filament and a bi-metallic strip that moved one or more contacts.

When the device is turned on, the filament starts to heat. As the filament heats, it also heats the bi-metallic strip. As the strip heats, it slightly bends, moving with it one contact. Once fully heated, the strip "bottoms out" on its limit stop. At this point, the contact is touching the second contact and allow B+ current to flow to the vacuum tunes.

The delay can be adjusted on some metal-cased units by turning a set screw that loads or unloads the preset tension on the bimetallic spring.

Time delay on the non-adjustable units was preset for the device's requirements and was set by either different bimetallic materials or filament thickness. If you need for a slower delay time, you'd simply install a resistor on one of the heater leads to limit the current going through the heater circuit. You could make the delay time less by giving the heater more voltage, but you will reduce the filament's life drastically.

These were used mainly in higher-tier electronics, test equipment and radio/TV transmitters. You'd rarely see them in AM radios, phonographs or TV sets.


www.stationalerts.com
www.jmarcoz.com

[Robert Gift]

Thank you, jmev.

Wish I had an adjustable delay relay.

Years ago I made a circuit which would turn on red lights when my cell phone rang at night. (Red so my pupils would remain dilated.)
I would get up, slip into my jumpsuit, put on shoes, and hopefully make it to the garage before the red lights lighting the way would extinguish.

Sometimes, the fixed 45 seconds was not enough.

[AllSafe]

... It's not a vacuum tube because the relay doesn't sit in a vacuum, but rather an inert gas.

Interesting! Thanks.
Why not a vacuum? Would that not be easier than an inert gas?
Did I see Getter in it? Guess not.
To determine gas, I'll have to look at the spark when the contact opens.
I never knew that filaments need be up to temp before B+ was applied.
180 seconds is a LONG time!
What kind of applications?

Radio transmitters, and certain amplifiers which often use very high B+ voltages. It helps with the tube life.

[JasonC]

That's really neat Eric. I tried my hand at making one but I got to picky. There are two things I didn't like, for one, you cant adjust the speed of the solenoids, and two, they don't gradually increase in speed like the real RCM flasher. It looks really good though and I cant wait to hear it!