Obsolete technologies you never knew existed

[Njk]

Unless one has seen the inside of a 1950s-era automobile radio, the vibrator power supply comes to mind.

Seen that in my father's car. A devices like that were sometimes called umformers. Produced a hum sound, similar to a cooling fan. BTW the old loudspeakers also produced some hum because there were no permanent magnets. Instead, the magnetic field was created by passing a (usually poorly smoothed) DC through a dedicated winding in the base part. The hum was quite annoying.

[TimFox]

The electromagnet coil in those loudspeakers normally was used as part of the rectifier filter circuit (filter choke) when useful permanent magnets were expensive or unavailable.

[Gyro]

The Scophony TV probably deserves a place in here. A pre-war large screen (24" x 22" domestic, much larger for theater) projection TV that got displaced by the advent of smaller, cheaper, radar CRT production during WWII.

The TV used a 300W Mercury arc lamp, mechanical scanning of line and frame frequency mirrors using valve amplifier driven motors (the line scan motor running at 30k+ rpm), capable of 405/441 line display. It also passed the light through a supersonic crystal driven liquid column delay line cell (Jeffree cell), synchronized to the line scan mirror which allowed a huge increase in light output compared to single spot scanning.

I remember a more in-depth article in an old issue of Wireless World but tracking it down is proving difficult.

https://www.earlytelevision.org/yanczer_scophony.html

[tggzzz]

In theory, yes, but in practice it was not that easy.

The inertia of phosphorus tubes is high, tens of ms, and depends from one TV to another.  Those who were selling the home computers were usually selling them without a monitor, and the buyer was using whatever TV was heaving at home.

Then, the CPU back then was clocked at only a couple of MHz, for example the ZX Spectrum from the video was with a Z80, an 8 bit microprocessor, and clocked at only 3.5MHz.  Same processor was handling the read/writes to the video RAM, plus the execution of whatever code was running.

The total screen was 384 pixels wide, out of which 256 pixels were the useful video image, and the rest were border.  A typical TV line has 64us, out of which about 12us or so (don't recall exactly) were sync pulses.  The fastest CPU instruction was taking 4 clocks at 3.5MHz.  During this CPU instruction, the electrons spot was traveling along 8 image pixels.  Not to say, most instructions were 2-4 times longer than the minimum possible 8 pixels.

The timing was very tight, and everything was heavily optimized.  Not much room was left to detect a pencil position.  There were no dedicated hardware counter/timers yet, like there are in the nowadays microcontrollers, so all timings were to be done in software.  If exact timing was needed, you were writing each machine code mnemonic in your loop on a piece of paper, and count the total numbers of clocks needed to execute one loop.

Or else, add dedicated hardware (for example a Z80 CTC, which was another chip on the same data and address busses, very similar with the nowadays PWM/counters from MCUs).  But adding hardware extensions was expensive.

The software speed you mention is irrelevant, since it has to be done in hardware.

With a little imagination you don't need a dedicated timer chip.

Data was stored in RAM, with that RAM's address changing every character (or bit) in synchrony with the screen position. Connect that RAM's address line to a dedicated hardware register's inputs. When the photodiode blips, clock the register thus storing the address related to the character (or bit) at that time. Read the register at your leisure, and use the relevant algorithms to convert it to the X-Y coordinate and/or relevant "object".

[tooki]

In some countries they had wired radio:


Sublime technology.

If I’m reading the comments correctly between the lines, it’s not radio at all, but just a public 100V PA system, and the little “receiver” is simply a small PA speaker?

[Njk]

If I’m reading the comments correctly between the lines, it’s not radio at all, but just a public 100V PA system, and the little “receiver” is simply a small PA speaker?

In fact, it was a cable radio system designed to make the user's terminal devices very cheap. Basically, the terminal can be just a loudspeaker and a small step-down transformer, since the line voltage was about 30 VAC to compensate for long length of the cable network. Later, the system was enhanced by adding two HF sub-carriers for two more programs. That required more complex terminals with the de-multiplexing capability

[tooki]

If I’m reading the comments correctly between the lines, it’s not radio at all, but just a public 100V PA system, and the little “receiver” is simply a small PA speaker?

In fact, it was a cable radio system designed to make the user's terminal devices very cheap. Basically, the terminal can be just a loudspeaker and a small step-down transformer, since the line voltage was about 30 VAC to compensate for long length of the cable network.

So… a PA system, just like I said? No actual radio (RF) involved.

Later, the system was enhanced by adding two HF sub-carriers for two more programs. That required more complex terminals with the de-multiplexing capability

Gotcha.

[RoGeorge]

The TV used a 300W Mercury arc lamp, mechanical scanning of line and frame frequency mirrors using valve amplifier driven motors (the line scan motor running at 30k+ rpm)

That reminds me of another now obsolete device, the ark mercury rectifier.  They were used a lot in the past.


Picture from https://en.wikipedia.org/wiki/Mercury-arc_valve

Some were about as big as a washing machine, full of high voltage and glowing!!! 


Another device in use for a while, electromechanical radio transmitters based on Alexanderson alternator.

One is still functional, transmitting once a year for the delight of VLF hams.

The Alexanderson alternator was a popular model in its time, and today, only a single perational example survives in the whole world. That machine, whose power output is 200 kw, is located at the Grimeton Radiostation, 10 kilometers (6 miles) east of Varberg on the Swedish west coast. While no longer in commercial service, station SAQ is still in an operational state and usually makes annual transmissions on 17.2 KHz.

Quote from http://www.jproc.ca/radiostor/aalt.html

[Bobson]

Unless one has seen the inside of a 1950s-era automobile radio, the vibrator power supply comes to mind.

Seen that in my father's car. A devices like that were sometimes called umformers. Produced a hum sound, similar to a cooling fan. BTW the old loudspeakers also produced some hum because there were no permanent magnets. Instead, the magnetic field was created by passing a (usually poorly smoothed) DC through a dedicated winding in the base part. The hum was quite annoying.

Nope. Umformers are motor-generators, having a motor and generator on one axis frequently with an aid of flywheel. I'm sure the correct English term is motor-generator, umformer is of German origin.

[Njk]

So… a PA system, just like I said? No actual radio (RF) involved.

Yes and it's still in use with exactly PA purpose as it does not require power. It's available in every household by default and the user have to pay a monthly subscription fee. User wishing to get rid of it have to perform the procedure with service cancellation fee.

[Njk]

I'm sure the correct English term is motor-generator, umformer is of German origin.

Germany is closer to Russia than England so German terms are historically in wide use. Generally, umformer means converter

[PA0PBZ]

Nope. Umformers are motor-generators, having a motor and generator on one axis frequently with an aid of flywheel. I'm sure the correct English term is motor-generator, umformer is of German origin.

I think that when both are on the same axis it's called dynamotor, not? And of course Dutch is close to German as usual, "omvormer".

[valcher]

I remember in the 60s of the last century in Christmas tree garlands they used incandescent lamps with a bimetallic plate to create a blinking effect. When current flowed through the lamp spiral, the plate heated up and opened the garland circuit, as it cooled down, the circuit closed and everything repeated again.

[RoGeorge]

You mean like this (closeup photo at minute 00:25)?



Still have on of those incandescent light bulb with bimetallic switch. 

Same idea of a bimetallic switch was used in the battery charger regulator in the first models of Dacia 1300 (a Romanian manufactured car).  Inside an isolated box there was a spiral of heating wire, and a bimetallic switch in series, to control the intensity of the excitation field of the car's alternator, thus regulating its output voltage.  In practice, that regulator was never working properly.  Everything was influencing its regulation, from temperature, to altitude, to humidity, to motor speed, to road type (because of vibrations), and so on. 

[squadchannel]

Christmas tree bulbs, until a ten years ago.
When they went out, the whole bunch would go dark, so I had my dad change them. can't even get the bulbs, so now they're LEDs.

[Gyro]

...
Still have on of those incandescent light bulb with bimetallic switch. 
...

I remember buying one of those as a kid. My dad wasn't happy when he had to start replacing other (fine but ageing) bulbs in the string!

Wiring a florescent lamp starter in series would produce a much more random flashing effect.

[CatalinaWOW]

Bimetal switches are a great example of a technology once widely used and dying now now.  Thermostats, blinkers for car turn signals and warm up timers are prior applications that are gone.  They still hang on in circuit breakers and thermal safety switches.

[TimFox]

An interesting technology analogous to bimetal strips is a piezoelectric "bimorph".
https://piezodirect.com/piezoelectric-bimorph/
A simple piezo actuator can exert a large force, but only for a very short expansion.
When a larger motion is required, the bimorph (described in that citation) allows a much larger "wiggle" at much lower force.

[coppice]

Bimetal switches are a great example of a technology once widely used and dying now now.  Thermostats, blinkers for car turn signals and warm up timers are prior applications that are gone.  They still hang on in circuit breakers and thermal safety switches.

Bimetal switches have been displaced from many applications, but I don't think they are going away any time soon. In many applications where it formed a controllable thermostat its being displaced by true temperature measurement devices, offering greater control. However, for things like a kettle cutout, when steam flows over a bimetal device, it needs little precision or controllability, and i think its likely to stick around for quite a while.

[valcher]

You mean like this (closeup photo at minute 00:25)?

Yes, this is exactly the type of light bulb

Wiring a florescent lamp starter in series would produce a much more random flashing effect.

Connecting the starter to the circuit caused unpredictable flashing of the lamps.

Thermal switches are still used in automatic switches, in protective relays for overloading electric motors, in thermostats for maintaining the temperature of industrial equipment control cabinets. It is too early to write off bimetal switches, they are cheap and reliable.

[SteveThackery]

However, for things like a kettle cutout, when steam flows over a bimetal device, it needs little precision or controllability, and i think its likely to stick around for quite a while.

Hey, @coppice, I'm not sure, but I seem to think most kettles use a "muscle wire" steam detector these days.

[Gyro]

No, bimetal is still pretty much universal. It can be formed into pre-stressed disc shapes where they exhibit a snap action of considerable force, rather than the slow action of muscle wire. Much easier to implement fast break contact actuators.

Edit: A typical example... https://www.eevblog.com/forum/repair/repairing-an-electric-kettle/msg5774927/#msg5774927

[Njk]

Hey, @coppice, I'm not sure, but I seem to think most kettles use a "muscle wire" steam detector these days.

This is my electric kettle. It has a quite complex mechanics inside the cap that requires periodic cleaning otherwise the steam detector switch does not work reliably because of high steam leakage. Also, it has a bi-metallic thermal switch that is proved very useful as it many times saved the kettle from overheating when all the water evaporated. About a year ago I'd modified it specifically to make the maintenance easy. Seems the time to do the maintenance again. Thanks for the reminder.

[coppice]

Hey, @coppice, I'm not sure, but I seem to think most kettles use a "muscle wire" steam detector these days.

This is my electric kettle. It has a quite complex mechanics inside the cap that requires periodic cleaning otherwise the steam detector switch does not work reliably because of high steam leakage. Also, it has a bi-metallic thermal switch that is proved very useful as it many times saved the kettle from overheating when all the water evaporated. About a year ago I'd modified it specifically to make the maintenance easy. Seems the time to do the maintenance again. Thanks for the reminder.

Our current kettle has an issue that when even a small amount of lime scale builds in the wrong place it starts behaving like a whistle when its only half way to boiling. A clean out with descaler and it goes quiet again. I'm not sure what it happening, since to far from boiling there shouldn't be much of a gas flow anywhere in the kettle to get such unpleasant whistles started. This kettle is pretty quiet when cleaned out. It has an arrangement at the bottom to break up the fine bubbles that form early, and make many flat bottom kettle chambers quite noisy.

[valcher]

Awesome teapot, the nuts and wire in the loop look especially cool