Using a Pot to Tune a Coil

Variable inductor:

Oh, you'll have plenty of time. Printing is slow, and you have to do two materials, one of which has a catalyst, and then you have to do all the electroless plating to get real conductivity for the windings.

Not on the scale of the uncertainty in a human-twiddled knob.

It's not any kluge-ier than zebrastripe elastomer connected LCD displays.

Did you hear about the 50F 2.7V capacitors that showed up recently? I've got one with a little LED glowing nicely, since it got charged about thirty hours ago. Time to resurrect the Marx generator moving-capacitors idea?

Yes! Forgot that one; used in some old Atwater Kent radios.

I guess if you were not fussy about frequency or (most especially cost), a custom design that (physically parallel construction) moves coil #1 between 2 others below it; those of opposite winding could achieve the variometer effect. Natch, SMT typically being small the frequency would have to be above most DC frequencies.

Darn, I was hoping to see taillight bulbs or teaspoons or mice or something glued down to a PCB.

I have a Tadiran lithium battery and a 1 Meg resistor and an LED hooked up as a night light. It's good for at least another 20 years. If you moisten your fingers and grab it, it gets brighter, enough to find your way around.

A classic rectangular multiturn wirewound trimpot comes close.

Do an image search for "variometer". Lots of interesting stuff.

But the layout is not conducive to (adjustable) transformer type coupling.

"U" wound one way, "N" wound opposite ----UUUUUU--NNNNN---- fixed primary ----UUUUUUUU--- siding/adjustable secondary

This as a crude "first article" for possible SMT variometer equivalent.

Seems the term has been "borrowed" for a type of instrumentation mainly used in airplanes...

One advantage of modern LED torches that use at least 3 cells is that you can bridge the on/off switch with 2M to have a torch that you can find in the pitch dark after the lights have gone out.

There are a couple of high performance passive phosphorescent materials now that will glow all night after a day spent in sunshine. GloTorch is a particularly good example and worth having if you live where the electricity is prone to going out during winter storms. This one:

No connection with the vendor just very impressed with it as a product that works much better than its advertising claims. I think the plastic they used is 3M technology and it works incredibly well.

Several imitations are rubbish by comparison.

I have a can of strontium aluminate glow paint, and it's impressive, scads brighter and longer lasting than the old zinc sulphide stuff. You can get that on ebay too.

We have some cute little old fashioned lantern looking things for power fails. They have an LED that blinks about every 10 seconds so you can find them in the dark.

And of course we have the bedposts with the tritium lamps, so we don't crash coming back from the bathroom in the dark.

They're illegal in the USA, so I order them from the UK.

We just don't have enough power failures to have fun with all that stuff. Nothing useful since the 1989 earthquake.

The shaft doesn't have to be insulated. Put the motor on the "ceiling", driving a horizontal metal shaft, with pulleys at intervals. The generators sit on the PC board with pulleys on their shafts. Tiny leather belts connect the drive pulleys to the generator pulleys. We're gonna party like it's 1899!

Oh. Hm. Maybe you could arrange the motor and generators with the shafts vertically, so you can solder the terminals on the other end to the board. Have one long belt run around to all the pulleys. (I've seen old ceiling fans done this way.)

Or: Get some photodiodes in SMT housings. Use them in photovoltaic mode, with enough strung together to get the voltage you need. Shine LEDs of the optimum color at the photodiodes. If you can get side- looking photodiodes and LEDs, it can all go on one board! If you can't, put the photodiodes in a row on the main board, and have a long skinny board full of LEDs that bolts down on top of the main board. Or, have the photodiodes and LEDs on the main board, both looking up, and put a mirror over the whole thing.

Matt Roberds

That's the One Prime Mover approach to industrial automation. One big steam-driven shaft that runs through a factory, with lots of leather belt pickoffs for lathes and things.

Yeah, I remember that from when I was a kid, a bunch of belt-driven ceiling fans.

We do use some PV optocouplers. They put out maybe 8 volts at 30 uA, which is enough for some uses. Efficiency is ballpark 1%. You can make a nice mosfet gate driver with a fast AC-coupled path (cap or pulse transformer) with the PV providing the slow, DC path.

We also build our own SSRs with the PV coupler, to get milliohm ON resistances that we couldn't find in a commercial SSR.

On Fri, 19 Jun 2015 19:09:01 -0700, John Larkin Gave us:

There is still a bar in Denver over near the ball park that operates all of its overhead circulation fans via a single motor and spinning overhead shafts with leather strap 'traction belts'. The whole setup is NOT a remake. It is a true, operating antique.

That was how the first HVDC systems were implemented. in this system several 3 kVdc generator where mechanically connected in parallel with leather belts and electrically in series to generate tens on tens of kV dc.

This is the way to go, if you need some serious isolation voltages. Let a laser feed a fiber and use some solar cells to generate some DC power to electronics working at elevated potentials (such as sitting on a 400 kV HV line). Use an other fiber to digitally send down measurements to ground potential.

I've seen an old lathe like that, meant to run off the Prime Mover shaft. The pulley on the lathe side is stepped to select the lathe speed. An adjustable idler pulley varies the belt tension, sort of a clutch effect.

Does it get very hot in Denver?

whole machine shops run like that,

must have been a deathtrap

-Lasse

The first LED Flashlight I bought was about 18 years ago at a hamfest. It used a 9V battery and was the same shape as 9V battery, but slightly larger. one of the selling points was you could find it in the dark. So, on the way home I had a flat. The kids had been playing with the flashlight and didn't know where it was, I turned of the dome light and said look for a dim light, one of the kids found it under the seat. Mikek

Cool. Yeah, life was cheap in those days.

Those pulleys are convex on the belt contact surface, sometimes very convex, almost half-round. That was counter-intuitive to me; I thought the belts would roll off the hump, whereas they actually climb up the hump.

Before uPs, there was an informal guild of traveling guys who designed complex machinery to make things, like stamped and bent metal gadgets, glassware, wireforms, all that stuff. All mechanical, often amazing.