What was your first circuit? Do you still remember it?

[vk6zgo]

A horse-powered drill? Wow. Did you get Swan or Edison to invest?

When you mentioned telegraph, I pictured you in a top hat and tails, working by lamplight 😁

Before electric & pneumatically driven ones, drills, were human driven, with a handle you turned on the side, or crank-like "brace & bit" style.
Until rechargeable drills appeared, it was often more convenient to use such drills rather than dragging heavy power cords around.
I cannot imagine any applications for horses in drilling.

[vk6zgo]

I keep planning to revisit those "regen sets" to see  if they were just crap designs, or if it was my poor construction techniques.

I don't usually quote myself, but I started digging through the old box full of "valves" in the back shed, & found a bunch which would work for those old projects---- maybe it is telling me something!

[brucehoult]

I cannot imagine any applications for horses in drilling.

Y'reckon?

[AndrewNorman]

For me it was the circuits in "Dick Smith's Funway into Electronics vol1".

Got given the book for Christmas, got the LED flasher working and then spent many hours trying to get the damned crystal radio to work. Never did manage, but it did get me interested in the subject.

[Kasper]

Mine was a battery, 2 wires and a light bulb following instructions in elementary school.  Then I made up my own circuit: a battery and 1 wire.

[capt bullshot]

I was probably 4 when I made my first circuit. Staple in the wall outlet.

Guess it wasn't a long lasting circuit, aka short circuit

[brucehoult]

I was probably 4 when I made my first circuit. Staple in the wall outlet.

Guess it wasn't a long lasting circuit, aka short circuit

Boom boom!!

(If you get the reference you're probably old. And Anglo, eh Derek?)

[PixieDust]

Here's my first circuit. I did the layout, the soldering and the cutting out on my CNC machine.

[hans]

My first circuit was at elementary school... the secondary school had a walk-along day, and one subject was physics.
We were given a battery and 3 light bulbs. They first showed a series connection and how you need a complete circuit to keep all bulbs lit. They then asked to rewire it that any bulb stays lit if another is unplugged. It seemed so intuitive to create a parallel circuit

Many years later when I built my first PCB, it had a 555 + 4017 on it to create a LED siren light for a small electric car.

[TomWinTejas]

My parents got me an electronics kit for Christmas when I was about 10 and I enjoyed playing with LEDs and buzzers.  But my first real project was for extra credit in my high school physics class.  I got the circuit from one of the Forrest Mims Engineer's Notebooks, the Optoelectronics one, which was an 'AM lightwave transmitter and receiver'.  I recall getting some crude fiber optic cable and showing how the refractive index allows for real world benefits.  Little did I know that all these years later I would be designing fiber optic networks for a career 

[Shay]

The first circuit I remember was in school, more or less try an error putting together 4.5 V batteries, lamps and switches. We somehow ended up in funny version that used 2 batteries, 2 lamps and a single, single simple switch in a way that either one or the other lamp was active.  It took me very long to find out how this could work and for this reason I still remember.

Probably this is still a nice puzzle for the beginners.

In simple switch, you mean a classic SPST switch?
2 Voltage sources, 2 lamps, a single spst switch, that either state turns only one lamp. that's the puzzle?

[brucehoult]

The first circuit I remember was in school, more or less try an error putting together 4.5 V batteries, lamps and switches. We somehow ended up in funny version that used 2 batteries, 2 lamps and a single, single simple switch in a way that either one or the other lamp was active.  It took me very long to find out how this could work and for this reason I still remember.

Probably this is still a nice puzzle for the beginners.

In simple switch, you mean a classic SPST switch?
2 Voltage sources, 2 lamps, a single spst switch, that either state turns only one lamp. that's the puzzle?

When I was about 10 our house was extended and a new hallway got a light switch at each end such that, of course, flipping the switch at either end would flip the state of the lights. That was fascinating!

You can do it using two SPDT switches and two conductors between the switches (and a 3rd that goes to the actual lamps), but I noticed the switches being installed were actually DPDT.

I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

I don't know if I've ever seen N>2 in the wild, so this result may not be well known.

[Shay]

The first circuit I remember was in school, more or less try an error putting together 4.5 V batteries, lamps and switches. We somehow ended up in funny version that used 2 batteries, 2 lamps and a single, single simple switch in a way that either one or the other lamp was active.  It took me very long to find out how this could work and for this reason I still remember.

Probably this is still a nice puzzle for the beginners.

In simple switch, you mean a classic SPST switch?
2 Voltage sources, 2 lamps, a single spst switch, that either state turns only one lamp. that's the puzzle?

When I was about 10 our house was extended and a new hallway got a light switch at each end such that, of course, flipping the switch at either end would flip the state of the lights. That was fascinating!

You can do it using two SPDT switches and two conductors between the switches (and a 3rd that goes to the actual lamps), but I noticed the switches being installed were actually DPDT.

I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

I don't know if I've ever seen N>2 in the wild, so this result may not be well known.

Nice. This is my crude solution to @Kleinstein puzzle:

L1 is parallel to B1, so by default it's on.
clicking on SW1 causes it to short L1 and B1 (would not recommend, but thats the best I came up with for theory) and puts L2 in series with B2.

[Circlotron]

I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

Schematic please!

[brucehoult]

I sat down with pencil and paper and figured out that with DPTP switches you can actually generalise this to an arbitrary N switches! I wired this up with 4 or 5 as yet not installed switches and a 6V lantern battery and torch bulb and demonstrated to the electrician that flipping any of the switches flipped the bulb state. He was stunned :-)

Schematic please!

Serious?

First and last switches only need one wire out, to the energy source and the lamp(s). Between every pair of switches one wire is hot and one wire isn't. Each switch either passes that straight though or else reverses which wire is hot.

It actually looks simpler on a physical switch because you're just connecting the 4 corner terminals out of the 6 in an X.

[themadhippy]

It actually looks simpler on a physical switch because you're just connecting the 4 corner terminals out of the 6 in an X.

6 terminals? were did you find these strange intermediate switches as every one ive used only has 4 terminals to keep it simples for us thick sparkys

[brucehoult]

It actually looks simpler on a physical switch because you're just connecting the 4 corner terminals out of the 6 in an X.

6 terminals? were did you find these strange intermediate switches as every one ive used only has 4 terminals to keep it simples for us thick sparkys

How on earth can you have a DPDT switch with only 4 terminals?

Unsurprisingly, 11 year old me in 1974 isn't the only one to come up with this.

https://forum.digikey.com/t/how-to-wire-a-dpdt-switch-as-4-way-for-multiway-switching/6985

[themadhippy]

How on earth can you have a DPDT switch with only 4 terminals?

Take a look at your diagram,theirs only 4 external connections needed ,and thats what you buy off the shelf from your electrical supplier,they go under the name of intermediate switch and do exactly what you described above,sit between  2 way switches to add a 3rd,4th -999th switching position.They really should rename them universal switch as they can be used for the most common switching arrangements found on lighting circuits.

[Calambres]

I remember my first circuit very well: a crystal (diode) radio. Then it came the Philips Electronic Engineer. I was fascinated:




I still keep the original manual:

[CatalinaWOW]

Similar path to many, first built was a 'crystal' radio based on a germanium diode, then on to a regenerative receiver based as I recall on a 12AT6 tube.  The first one I designed myself was a dual slope A-D converter.  That had maybe 5% accuracy, drift so bad that only the lack of accuracy saved it, 8 bit resolution and several samples per second conversion rate.  But I was still proud of it.  Boy did I have a lot to learn.

[TimFox]

Mine was a code-practice oscillator that I built in Cub Scouts, ca. 1960, similar to the one in the QST article linked below.
It used a CK722 PNP germanium transistor from Raytheon.
That, and the GE 2N107 NPN transistor, were heavily advertised to young people at that time.
IIRC, they were both about $2.50 each back then.
https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1959/07/page30/index.html

[brucehoult]

How on earth can you have a DPDT switch with only 4 terminals?

Take a look at your diagram,theirs only 4 external connections needed ,and thats what you buy off the shelf from your electrical supplier,they go under the name of intermediate switch and do exactly what you described above,sit between  2 way switches to add a 3rd,4th -999th switching position.They really should rename them universal switch as they can be used for the most common switching arrangements found on lighting circuits.

Well great if this is common enough they make specialised switches for this. I've only seen general-purpose DPDT switches, but I'm a hobbyist doing low voltage stuff not a sparky, and 6 terminal DPDT switches are possibly the MOST common kind.

https://sparks.gogo.co.nz/catalog/Buttons-Switches-Relays-261/Miscellaneous-100/DPDT--AB--Small-Panel-Mount-Toggle-Switch-6mm-Thread-1015.html

[TimFox]

A DPDT switch hard-wired to only four terminals is often called a "reversing switch", or in US domestic lighting a "four-way switch", which is connected between two or more "three-way switches" (SPDT) to control lighting along a corridor, etc.

[themadhippy]

.6 terminal DPDT switches are possibly the MOST common kind.

in the electronics world agreed,however what surprised me is

but I noticed the switches being installed were actually DPDT.

as ive yet to see a dpdt switch in a standard light switch  format

[mawyatt]

Mine was a code-practice oscillator that I built in Cub Scouts, ca. 1960, similar to the one in the QST article linked below.
It used a CK722 PNP germanium transistor from Raytheon.
That, and the GE 2N107 NPN transistor, were heavily advertised to young people at that time.
IIRC, they were both about $2.50 each back then.
https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1959/07/page30/index.html

Remember those CK722s, one of the early plastic cased transistors. You could shine a light on them and they responded!!

First project here was a telegraph made from old scavenged lantern batteries, scrap phone wire, tin can top, scrap nails and scrap wood 2 by 4s. Tin top was cut for telegraph "key" with nail contact, and the "T" shaped "sounder" and wire wound around 2 nails as electromagnet. Was 6~7 then and parents thought I was nuts, they were probably right

Fond memories from back then!

Best