At electronics flea market yesterday, I got an ignitron to play with.   The uncommon glass envelope lets us see the mercury, and will let us see the plasma glow.  Tube might serve as an acoustically quiet switch for my old can crusher, subject to concerns about peak current and current reversal.
Does anyone here have hands-on experience with ignitrons, and high voltage pulsers to drive the igniter pin?

This seems like the least wrong subforum for a chemistry topic.

For many years I've ingested a few pills each day, from a short list that recently includes "Calcium supplement".  Just finished a bottle of 500 pills, and opened a new one.
The label says 600 mg, and I wondered if that's the weight of calcium or that of calcium carbonate.
For reference, my daily iron supplement (since I donate blood) is labeled with weight of ferrous sulfate.
Water hardness measurements (in ppm, grains/gallon, etc) indicate equivalent weight of calcium carbonate, even if no carbonate is present.

Weighing some pills gave the answer.   Looks like each pill is made with 1.5 grams of CaCO3, which includes 0.6 grams of Ca.
In 16 months I ate 750 grams of chalk, costing more than $20.
The same money could buy 750 kilograms of crushed limestone at a rockery!

What's a good hobby use for 10 kilojoules of 63 volt aluminum electrolytic capacitors?
I'm here to share some things learned from a "bank" that was saved from scrap bin, when an old storage room was converted to a new lab.

These 14 aluminum electrolytic capacitors came in metal support frames that don't hold them tightly.
Each is nominally 280,000 uF 63 volts, with an individual 4700 ohm parallel resistor and individual wires to ring lug terminals. (10 kJ claim will follow.)
Two screws and two nuts were sufficient to connect the whole set in parallel.


First step on the test bench was to reform the capacitors. a chore that's not only for antique or high voltage capacitors.
(Note the reforming protocols that come with industrial VFD's, for units put in service after more than 12 months of storage.)
https://www.eaton.com/content/dam/eaton/products/industrialcontrols-drives-automation-sensors/variable-frequency-drives/powerxl-dm1-variable-frequency-drives/vfd-storage-and-reforming-capacitors.pdf
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Using 0-50V benchtop power supply and 10 ohm series resistor, I progressively set the voltage to 20V, 30V, 40V, 50V over a few hours.
Final current was a steady 0.15A, which can all be attributed to the bleed resistors with 48.5 volts on bank.

Let's measure the capacitance.
With PS disconnected, voltage dropped from 48.48 to 46.47 V in 1 minute, indicating RC product of about 1416 seconds.  If the average R value is nominal then average C is 0.30 F and whole bank is 4.2 F.
I also discharged the bank for about 10 seconds into the 10 Ω 50 W resistor.  Bank voltage fell from 48.5 to 37.1 V.   About 1900 joules made the resistor very hot; I didn't bother looking up energy ratings in its datasheet.
At the end of the session I disconnected PS and monitored the voltage during bleed-down.   Time constant exceeded 2000 seconds (more than 150% of nominal) at lower voltages.  That inspired an exercise (to be reported later) with automatic voltage logging.   Will also describe bringing the bank up to 63 volts, measuring voltage dependent leakage current and capacitance, and dielectric absorption (voltage bounce-back after not-rapid partial discharge).

Most burned-out incandescent lamps can be given new life by applying high voltage.
Here's a semi-burned-out lamp that came out of my car this morning.   Type 9003 "Quartz-halogen", 12 V, 55 + 60 W.


What if we apply high voltage, for example from NST on variac, between the apparently open terminal and the other two.
Will we get an arc between broken ends of filament, or between exposed metal parts outside the fused-quartz envelope?
If inside, does anyone want to guess the voltage at 30 mA or 1 mA?

Would the electrical behavior of low-beam circuit be substantially different if globe is heated, by operating 60 watt high beam for a while?

Here is a new branch of the experiments reported in thread: https://highvoltageforum.net/index.php?topic=2299.0

We had characterized a small LC tank circuit, using a bench-top signal generator as power source.
Theoretical maximum power is around 1/2 watt into 50 ohms.

Let's try heating a thermometer.   I had not previously seen that done by induction.
Mercury should be easy, only 1.8% as conductive as copper, even though Hg is not ferromagnetic.  (Chart includes nickel to represent a ferromagnetic element.)


Coil is 26 AWG magnet wire on plastic tube from a ball-point pen.


Estimated inductance was about 2 uH.  First run was with a capacitor measured to be 0.333 uF, resonating at 186 kHz.
To better match the signal source impedance, I reduced C to 0.230 uF and then to 0.099 uF, which resonated at 340 kHz.
That slightly increased the indicated heating rate, to about 0.5 degree per second.  I cluttered youtube with a video.

These charts show voltage measurements with empty coil (blue) and with thermometer bulb in the middle (orange).


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There's been news lately about unexpected purpling of street lights.
Here's a good article, which points the finger at delamination of yellow phosphors, after problems with manufacturing quality and/or thermal design.
https://www.businessinsider.com/led-city-streetlights-turning-purple-broken-tech-danger-2022-11?op=1
So it was delightful to see an example near home, in this case on El Camino Real at BMW dealership in Mountain View, CA.
I bet nobody makes that size luminaire in purple on purpose.

Tired of waiting for overdue toy "ZVS Induction heaters" from ebay, I made a practice coil and measured it on the bench.

With an ordinary benchtop signal generator I was pleased to get tank circuit ringing with more than 10 amps RMS at 126 kHz.  49 volt-amps, from a 50 ohm function  generator that can put out up to about 0.6 watts.  Here are the details.

For lecture hall and SPICE simulations, I wanted to start with 1 uF and 1 uH, to get time constant 1 us (Fres = 159 kHz) and characteristic Z = 1 ohm.  The blue capacitor, which helped me blink a neon glow lamp more than 50 years ago, was just measured to be 1.001 uF!   The coil was wound today, starting a bit on the large side. Tank resonance at 126 kHz implies L = 1.6 uH.

Connections are made with BNC cables and a BNC tee at oscilloscope input. Scope input is high-Z, and the transmission lines are negligible at this frequency.
With LC tank unconnected, maximum output sinusoid was measured by scope to be 31 V peak-to-peak and 10.94 volts RMS.  If source impedance were nominal then we could drive 5.47 V into 50 ohms, for 0.60 watts.
After connecting LC tank and adjusting frequency for maximum voltage, I recorded 4.70 volts RMS at 125.5 kHz.   Computed current amplitudes are 10.5 A RMS in both L and C.  Review of my arithmetic would be welcome.   Don't know if capacitor would become warm.   Power lost in tank can't be exceeding 0.6 W.

Next steps are to measure change in resonance with repeatable ferrous & nonferrous loads in coil.  Or for Solhi's interest, measure B at center of coil using a small sense coil.

[edit] Has anyone seen evidence of volt-amp ratings on IH's or IH capacitors? It seems natural that the value would be product of RMS voltage and RMS current in the tank circuit.  A very generous upper bound on heating power.

Before laser pointers existed, one could point out details in a projected image using compact non-laser pointers.   Here's one from Hama, in picture snipped from an ebay listing today.
I have some replacement lamps, with special V-shaped filaments. A sad reminder of going-out-of-business sale at our local everything-photographic store.  Note strange shape of glass envelope. 

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The other day I fired one up and projected its arrowhead shape using a small lens.

As with any optical projection, the brightness on screen depends on the source luminance, the magnification, and the lens speed (f/ ratio).   Luminance is the apparent brightness of a distributed source, for example what photographers measure with a spot meter.  A traditional unit in USA is the footlambert;  SI unit is the candela per square meter, also called the nit.  Brightness of TV, computer, and phone screens can be hundreds of nits. 

For this bulb, as with tungsten-lamped slide projectors and movie projectors familiar to we boomers, the limit is on order of 10 meganits according to literature.  (Solar disk is in the low giganits.  Slightly higher viewed from surface of Mars.  If a cheap laser diode has uncollimated brightness of 1 Cd from emitting area of 3 square microns, that's 3E+11 nits! )

Here's a SWAG of luminance for the V-shaped filament in picture.   Say 5 mm length of 0.05 mm straight tungsten wire, for luminous area of 1/4 square mm.   If the luminance were 10 meganits, the uncollimated lamp brightness would be 2.5 Cd on axis.  Feels about right. [edit] I guess that when properly measured, the wire thickness and lamp candlepower will both be higher.

In high school I played with cooking wiener sausages by applying 120 volts along the length.   In last week's storage cleanup I found a commercial product that does the same thing.
It still works.

Next exercise is to measure the current.  I bet it will increase as the hot dog gets hot.

Cordless mouse on this PC failed a few minutes ago, and I suspected its battery. 
Swapped the battery, a single AA cell, with one in a quartz-regulated, analog-faced wall clock.

Apparently the mouse needs less juice than the clock.
Mouse is working fine with ex-clock battery.
Clock second hand is barely twitching with ex-mouse battery, even with clock in horizontal plane.
Normal failure in a wall-mounted clock leaves the seconds hand pointing to 9, and clock runs longer if laid flat.

Has anyone here tried a "joule thief" LED blinker circuit,
with a battery at the point of failing in mouse or clock service?