I've been more or less lurking here waiting for more information on what the "DEVICES" are. It appears that they present two terminals with 12 to 24 volts DC, available from "something" whenever an LED on the DEVICE (or somewhere else) illuminates. Or perhaps the voltage is always there. When the LED lights up we need to "short" those two terminals together, whereupon something happens in the DEVICE about a quarter second later, perhaps extinguishing the LED that got the ball rolling. After that, who knows? Does the 12 to 24 V DC source go away after the terminals are shorted? How much current is sourced from the two (shorted) terminals while the LED is on?
While working in the 1960s and 1970s as an electronics technician at a local research institute, way before I eventually graduated with a BEE degree, an electrical engineer there sort of took me under his wing and mentored me. Karl was of old German descent and did not come from a wealthy family, so he was always looking for the cheapest and simpleist way to get things done. He had managed to accumulate a bit of wealth, purchasing a nice stone house modeled after an European castle (complete with secret hidden passages) located in a wealthy suburb adjacent to Dayton and within walking distance of the research institute. I lived in a more modest abode on the other side of the railroad tracks (literally!) but also within walking distance. I still live there, but Karl had to sell his wonderful house for reasons not important to this tale. Anyway, we both often worked late into the night because the work was so interesting. We were both salaried, so there was no extra pay for the extra hours. We just loved all things electronical, electro-optical, electro-mechanical, and whatever electro-fill-in-the-blank we came across during our research activities. There were a few other professionals and even one or two professors who worked the same kind of hours simply because they really enjoyed their work. I think most of our peers thought we were nuts.
Anyway, because of the late-night hours, Karl would often receive telephone calls that he didn't answer because the phone was in his office and there was no phone in his lab. These were ordinary multiline desk phones connected to a Centrex switch. Each phone had two to four buttons that would light up and blink when that line was ringing or illuminate steadily when the line was in use. Karl's simple and cheap solution was to rig up a cadmium sulfide LDR inside a rubber boot that slipped over a button on the desk phone. He may have had one for each button; I don't recall that detail. He strung a pair of doorbell wires (like is used in house doorbells) to his lab and connected them to a 12V battery and a doorbell. If a button lit up, the CdS resistance would drop low enough to ring the doorbell and alert Karl to run to his office to answer the phone. Of course he had to remember to disconnect the doorbell battery before he answered the phone and re-connect when he returned to the lab. Karl didn't have the best short-term memory in the world. He would often write notes to himself on Hollerith cards and place those cards in his jacket pockets to serve as reminders. No hole punches necessary for the data, just a pen or pencil. I am of an age where that "memory jogger" technique is beginning to look attractive, although my Galaxy 4 smart phone can also store notes... if I can remember how to do that. But where can I buy a box of blank Hollerith cards, except maybe on E-bay $5.35 for 15?
@KrisBlueNZ: I did do the introduction page here. The "h" in hevans1944 stands for Howard or for my nick-name, Hop. 1944 is when I was born on Sunday, June 25 at 12:10 PM (local time in Welch WVA). I just now got around to liking your post #25! Sure wish we knew how much current the 12 to 24 V DC DEVICE can source. Power MOSFETs are nice, especially in Class D amplifiers.
@(*steve*): Have fun with your PUT! Just remember to put a current limiting resistor in the cathode lead if you are discharging a capacitor through it. The maximum energy it can handle is only 250 μJ, so size the capacitor and its charging voltage accordingly so as not to let the smoke out: 1/2 CV² < 250 μJ should be safe enough bearing in mind that V is exponentially decreasing. Or maybe use SPICE to simulate the circuit first, although I have no faith (like Bob Pease) that SPICE simulations resemble reality. You gotta understand the physics first!
On tunnel (or Esaki) diodes: Tektronix briefly flirted with these for triggering time-base sweeps in one of their oscilloscopes. Too finicky for a field instrument. I think I remember a "grid dip" oscillator circuit that also used a tunnel diode oscillator, but that didn't catch on either. The tunnel diode did garner a Nobel prize for Esaki though, not to mention advancing quantum physics.
If your interest includes microwave frequencies above 10 GHz or so, the Gunn diode or TED (transferred electron device) makes a robust oscillator when inserted in a tuned cavity. Radar speed guns use Gunn diodes and they have also been used by radio amateurs. Wikipedia has a nice
article on Gunn diodes.
Sadly, except for a short tour in the USAF, and some propagation experiments at 70 GHz at the research institute, my practical microwave experience has been nil. Unless you can find surplus parts (waveguides, circulators, Magic-Ts, micrometer tuning stubs, horns, parabolic reflectors, etc.) and surplus test equipment, it is an expensive pursuit.
73 de AC8NS
Hop
)
