On Monday 04 November 2024 04:44:27 pm wn4isx wrote: Speaking of things that have gone away, I miss unijunctions. I have about 2 dozen and pick projects for them with great care. PUTs suck bilge water on a good day.
What do you have against PUTs? I think I may have one UJT, I ran across something and just looking at it I was thinking about picking up some of those. You can do a pretty good simulation of them with a cross-connected complementary pair. Use that as an SCR, SCS, PUT, all sorts of ways. Not sure if you could make it act like a Schockley diode or not, though. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
On Monday 04 November 2024 04:09:10 pm wn4isx wrote: Somewhere I have GE light bulb manuals [in PDF] from 1960ish. NE-1 were wire lead with no resistor, today the NE-2 looks to be the same. On my server I'm pretty sure I have the "GE Glow Lamps" manual. If it's not on my web site I can put it up there. Try a Google search for "Neon NE-1 bulb."
My father bought me 500 from Burstein-Applebee when I was 10. I still have more then I want to count. I remember that company, though it's been a really long time since I've thought of them. Are they still in business? Why 500 of them? Neon bulbs can be fun. Certain organs that I worked on used them in frequency divider stages, and sometimes the vibration in the console of the lower notes would cause a lead to break, giving a missing note, or several. In those units you could take out a couple of screws and swing the chassis out into a horizontal position, and it was easy to observe which bulbs didn't light when you pressed keys. I always wanted to get some of the ones that it up in different colors because different gases in them. Like some VR tubes do. I'd probably play with them some more if I had a suitable power supply, but haven't so far felt motivated to build one. On those salvaged flash units, there are two types, most were (?are?) small xenon strobe tubes, probably have a life of no more then a few hundred flashes, the other uses white LEDs. These all have the flash tubes. How do you figure they have such a short lifetime? The ones with the xenon strobe will have a ~300uF 300~400V capacitor that will light you up but good. That cap is very apparent on these units. Been there, done that and still feel the zap. I mean be careful with those tube ends and capacitors! They have enough energy to stop your heart. Use the "keep one hand in your pocket" technique.
Look up " xenon strobe circuit diagram" on Google for examples of how they are constructed.
Unless you need a really bright light that lasts a 1/1000 of a second, I'd be really tempted to send them to the electronic recycler. I figure to play with 'em one of these days. I no longer work on tube guitar amps because of the high voltage. I've worked with 24V and less for most of my professional life. My brother is very much into tube guitar amps, for the sound of them. I have a power supply and amplifier chassis and speakers out of an organ that was scrapped, and my intention is to make a guitar amp out of that. One of these days. 1V of video won't fry your ass. [most of my professional life revolved around 1V of video and 0dBv of audio]
Marshal made an amp with 1200V at 500mA B+. I very much doubt that. Maybe half that much. I used to be a Marshall service center, and probably still have schematics around here someplace. We had a tech get zapped and stopped breathing. We managed to get him breathing but it was a way too exciting 5 minutes. The boss buttoned up the Marshal and told the customer, "We don't work on these." Sounds to me like he got careless... I suspect many (?most?) members in this group have limited education in electronics and fail to appreciate all the dangers. Back when I was into messing around with chemistry experiments I tried electrolysis, but found operating from batteries (which were probably prett much at the end of their useful life anyway) to be abysmally slow. So I took a selenium rectifier that I had handy, rigged it up with a line cord, and was very pleased with the results. I had to keep adding water, and was surprised at how dark the water got after a while. Put me off of drinking tap water for a good long while, that did. I was probably 11 or 12 at the time, I strongly suggest purchasing a "stand alone" Ground Fault Interrupter/Residual Current Sensor and never work on any mains powered device that is not plugged into that outlet! Got one of those in a short extension cord kind of format, but pressing the test button doesn't do anything. I might have to investigate that one of these days. I used
until I had time (and mobility) to wire in real GFI outlets.
~$15 is cheap insurance. Not something I worry about too much. I started out in electronics when tube gear was still pretty common, all over the place, actually. Ran a TV repair shop for a bit, and it was mostly tube gear in those days. I only got zapped good one time, ignoring the warning on a sticker in a zenith TV set and gouging my arm on the lip of the metal cabinet on my way out of there. That's about 25KV or so, and is probably the worst I've ever gotten zapped. One of the first bits of stuff had to do with a course my father was taking (that I ended up finishing). They had a 5x7x2 metal chassis with a 35Z5 rectifier tube and a light bulb in a socket, line powered of course. One of the things you were supposed to do with it was connect the output wires to nails stuck in a potato, and observe the different behavior near each of the nails. That things gave me a good tingle or two when I was messing with it. Unless you know why, have all your equipment powered from the same outlet, use high quality metal power strips. I have some power strips, but also DIY some of that stuff, outlets in electrical boxes with a line cord attached, etc. And forget Variacs and mains isolation transformers until you understand their limitations and safety risks they can add. Got both of those, and I know how to use them. And also how to get by without them. I can still remember one TV I was working on where if you plugged the (non-polarized) plug in the right way the chassis was grounded, the other way it was hot. So I'd check this every time I plugged it in, until the one time I forgot to do that, and damn near vaporized a ground clip of my scope.... I started messing around with radios when I was 4, crystal radio, AC mains radio when I was 7, got my ass knocked off, look up All American Five. I don't have to look it up, I know it well. Both the octal and the miniature variants. Built one in shop class back in high school. Where I doubt very much that they even have that shop class any more. By the time I started formal electronics education I'd survived most of the stupidest stunts one can do and learned safety the hard way. Yup. that's how that works. My father once told me "Son if you're determined to be stupid you'd better toughen up." This was over Sunday lunch and my family broke into hysterical laughter.
The idea of "Terry toughening up" is still funny.
Please be careful. That's a matter of course. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
That's funny because my first exposure to a dictionary was one
from Encyclop?dia Britannica? -- and the associated set of
encyclop?dias didn't give me much training in American spelling
either.
Donald.
On 11/5/24 10:33, wn4isx wrote:
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Are you in the USA or GB?
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PCP was most often called angel dust in the USA in the 1970s
~ ?1990s.
PCB, Polychlorinated piphenyl was almost always called PCB.?
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We could well be seeing "one people divided by a common
language."
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My grandmother gave me a dictionary for Christmas in the 3rd
grade and I started having trouble.
The teacher couldn't understand how I could mispell color as
colour and when I argued "But that how my dictionary shows it!"
she had me bring it in. Somehow my grandmother had gotten a
Canadian dictionary.
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I still tend to spell plow plough unless I catch it.
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It seems that DIAC could be seen as two Shockley diodes connected in anti-parallel.
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
On 11/4/24 23:10, Andy wrote: You might want to insure it doesn't have PCB. Many highvoltage capacitors
used that crud.
Polychlorinated biphenyl is often called PCB. Scary stuff according to the Wikipedia article about it.
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
bbbOn Mon, Nov 4, 2024 at 05:58 PM, wn4isx wrote:
You might want to insure it doesn't have PCB. Many highvoltage capacitors used that crud.
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I think you mean PCP, not PCB.? PCBs are mostly harmless - although they might not react too well with multi-KVs unless they are clean.? PCP, on the other hand, is quite problematic and hazardous.
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Many years ago there was a guy in town (he started this little company called "Radio Shack", yes the same one) who had some surplus transformers in his yard.? They started to leak, and they were leaking PCP stuff.? That got the hazmat guys there in a hurry.
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Andy
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
Thanks for reminding me. It is about 40 years old so that is a very good possibility. Bertho ?
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From: [email protected] <[email protected]> On Behalf Of wn4isx
Sent: 4 November, 2024 17:59
To: [email protected]
Subject: Re: [electronics101] LED Flasher circuit why won't it work? On Mon, Nov 4, 2024 at 05:36 PM, Bertho wrote: I still have one sitting in the attic, but I have not found a good use for it.
You might want to insure it doesn't have PCB. Many highvoltage capacitors used that crud. The hazmat people had a meltdown when a power factor correction factor capacitor in our small transformer room had oil seeping out around the terminals, testing showed it was PCB. They downed our power, removed the transformer and took swabs around the room looking for PCB. That was an area that was off limits to us engineers, only the building engineers had access to that sacred room. They placed the capacitor in a large plastic container, dumped "kitty litter" around it and then put a snap lid that couldn't be removed and sent it COD to GE, the manufacturer.
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
This thread brings back many memories about strobe tubes. Decades ago, I used to work on big industrial YAG lasers. The YAG bar was strobed by an intensely bright light flash for producing the laser pulses. There were two capacitors with a working voltage of around 2,000V. They were bigger than the airplane carryon wheeled travel cases. I was extremely careful around them. I still have one sitting in the attic, but I have not found a good use for it. By the way, the strobe tubes were water cooled. Bertho ? On those salvaged flash units, there are two types, most were (?are?) small xenon strobe tubes, probably have a life of no more then a few hundred flashes, the other uses white LEDs. ? The ones with the xenon strobe will have a ~300uF 300~400V capacitor that will light you up but good. ? Been there, done that and still feel the zap. I mean be careful with those tube ends and capacitors! They have enough energy to stop your heart. Use the "keep one hand in your pocket" technique. ? Look up " xenon strobe circuit diagram" on Google for examples of how they are constructed. ? Unless you need a really bright light that lasts a 1/1000 of a second, I'd be really tempted to send them to the electronic recycler. ?-----------------
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
I used to know, but perhaps I am wrong, that the "avalanche mode" has a negative resistance after breakdown. It is not the case for "zener mode".
So, if the junction BE of a transistor at breakdown follows the avalanche mode (not the zener mode), the OP's circuit can oscillate.
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Kerim
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
On Monday 04 November 2024 03:27:22 am wn4isx wrote: I've seen a 2N2222 used in avalanche mode to drive a xenon strobe. It feels as though they used the C/E connections across 120 with a series resistor and capacitor similar in how a NE-1 relaxation oscillator was wired. When I saw it I didn't believe it possible. This would have been the summer of 1976 because a local company was making xenon strobes for a local Bi-Centennial event.
I couldn't believe the low parts count because I had constructed a xenon photo strobe for my father. I never heard of an NE-1, which I thnk you've mentioned more than once. I know NE-2 (wire leads), NE-51 (bayonet base) and the H (high brightness versions) of these. I also recall NE-45, which was a screw base with a built-in resistor for 120V, I had an old tape recorder once that used a couple of these for level indicators. I thought they were kinda nifty, but the last time I looked the pricing on them was silly. On flash units, at one point my brother was working for a photo processing place. I got him to snag me some of the flash units that were removed from those disposable cameras. Aside from a brief look, I have't taken the time to figure these out. There's a pair of battery contacts (which polarity?) for a AA cell, and two sets of switch contacts, one to turn the flash on and one to trigger it, but reverse engineering them is something I haven't gotten around to yet... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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On Sunday 03 November 2024 08:25:26 pm wn4isx wrote:
[1KV CDS cells? Say it ain't so. I use them for V+ or Vgnd to base <I tend to use NPN transistors>, even 120V frightens me silly!]
I seem to recall a part that was popular back when, called the "LDR-25", the letters standing for Light Dependent Resistor. And the numbers meaning that the thing could dissipate 25 watts? There were some projects with that thing running off of line voltage. Look in Popular Electronics "Solid State" or "Transistor Topics" (earlier) for these. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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On Sunday 03 November 2024 07:36:27 pm Andy wrote: If I'm not mistaken, these days CdS photocells may be hard to come by.? They are toxic (HIGHLY toxic, I am told) and I think have been banned for a while now in most parts of the world.
Bummer. They still seem to be fairly reasonably obtainable from various chinese sellers, on ebay, etc. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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On Sunday 03 November 2024 07:23:57 pm Andy wrote: Note, by the way, he is talking about a *Shockley* diode -- *NOT* a *Schottky* diode.? They are rather different beasts, named for different physicists. An important distinctions, there. I never ran into a Shockley diode before, but I heard of them.? Neither have I. I do remember them showing up in various magazine articles, though. One that comes to mind was by Don Lancaster and had the diode stimulated at some audio rate (near 400 Hz IIRC) and in turn stimulating a tuned circuit, useful for aligning AM radios or somesuch. It was amazing in its simplicity. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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On Sunday 03 November 2024 01:31:59 pm wn4isx wrote: I'm posting these to give people ideas on practical experiments.
This was fascinating, a introduction to physics teacher taught me this trick in high school
I hadn't really thought of CdS as a semiconductor... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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Re: Miscellaneous (was: LED Flasher circuit why won't it work)
Your comments remind me of using the avalanche mode to drive MHz ultrasonic transducers over 40 years ago. The DC supply was about 300 V and the pulses in the ns range. I controlled the base voltage to keep the transistor from avalanching and pulsed the base to trigger the breakdown.? I got to look up the details. Bertho ? From: [email protected] <[email protected]> On Behalf Of wn4isx
From my days in EE class (1973~1979) Motorola and RCA referred to avalanche mode as "breakdown that collapses to (near) zero." Much like a 4 layer Shockly diode. A zener or normal BE/BC breakdown stabilizes at the breakdown voltage, where "avalanche" (as used by Motorola way back when) refers to a switch like action. The 7nS pulse generator I gave a link to uses a transistor in what I was taught was avalanche mode. The 90V charges a capacitor through a resistor, at some voltage the C/E junctions avalanche and produce an unholy narrow pulse. I built the circuit using a NE555 driving a complimentary pair driving an 8 ohm to 1K followed by a voltage quad or quint (5) multplier. The transistor type, and I think (if I remember correctly) manufacturer were important. I know not all Motorolas worked, most did and I think no RCA worked.
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Re: LED Flasher circuit why won't it work
wn4isx wrote:
I can't see a B/E junction going into avalanche mode.
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Why not?
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Whether you call it "avalanche mode" or "zener mode", for most of us engineers that is less important than the fact that it breaks down due to reverse voltage across the junction.? Almost all modern BJTs have a base-emitter breakdown voltage that is rather low, about 5 V.? (Whereas the breakdown voltage of the base-collector voltage is generally considerably higher and it varies over a wide range, and depends on its part number.)
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I am not certain but I'm pretty sure that is what the circuit dues, in the original poster's message.? Base-Emitter breakdown.? Not base-collector.
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(Technically, "avalanche mode" breakdown refers to reverse breakdown that is greater than about 5 V or so.? At the physics level, they are rather different mechanisms, but the transition from zener mode to avalanche mode is gradual and there is a range where they overlap.)
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Andy
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If I'm not mistaken, these days CdS photocells may be hard to come by.? They are toxic (HIGHLY toxic, I am told) and I think have been banned for a while now in most parts of the world.
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Bummer.
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Andy
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wn4isx wrote:
The LED flasher question brought up a memory from the early 1970s. The 4 layer Shockley diode acted like a solid state switch, ...
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Note, by the way, he is talking about a Shockley diode -- NOT a Schottky diode.? They are rather different beasts, named for different physicists.
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I never ran into a Shockley diode before, but I heard of them.? I had much more hands-on use with Schottky diodes.? OTOH, I often refer to the Ideal Diode Law or Equation which is also known as the Shockley Diode Law.? Mr. Shockley is credited as being one of the three inventors of the (bipolar) transistor at Bell Labs.
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Andy
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Re: LED Flasher circuit why won't it work
FYI -
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The first time I saw this effect described as if it was a "new" (previously unknown) effect, it was in a Youtube video where they had access to a curve-tracer and other lab equipment.? The fact that it was Youtube dates it to late in the history of transistors.? The effect was known for decades already.? It's just that people forgot to think much about it.
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If I remember correctly, that video also showed a working relaxation oscillator, blinking a LED.? IIRC, they used a 2N2222.
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Andy
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Re: LED Flasher circuit why won't it work
I am guessing that the reason for building that circuit, was to see that it does what they say - not to make a LED flasher per se.? It exploits a rarely utilized (and usually but not always harmless) property of bipolar transistors.? Some would say that it is not well understood, but I think that's wrong, because all PN junctions have a breakdown voltage.? It just happens that the doping profile of most transistors in the base-emitter junction is such that this breakdown voltage is rather low, only around 5 V or so.? That does not affect the transistor's normal operation.
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It is easier to see the breakdown by putting the transistor on a BJT curve-tracer that sweeps out its curves.? I am not an expert on making relaxation oscillators from that sort of nonlinear effect, so I can't advise the O.P. about what to do to improve it, without investing a lot of additional thought.
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If you want to see this effect working:? Go for it!? Keep trying.? It might not happen at first, or even at all.
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If you want to make an LED flasher:? Try something? else.
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(By the way, most SPICE transistor models do not include breakdown of the B-E junction, so simulations won't show it either.? That fact has probably caused many to conclude that the effect is unknown, but that is incorrect.? Some SPICE models do include it - but I can't remember now whether they could simulate relaxation oscillators like this or if there is another subtle property that is also needed.? Darn fuzzy brain cells.)
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Andy
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Bertho