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Topics - klugesmith

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1
Space-X plans to test-fly their "Big Falcon Rocket" for the second time this Friday, after receiving the necessary government permits.

Here are some comments about one of the announced design changes since the April 2023 test:
improvement to the "flight termination system" required for range safety.
A typical report of the April event says: "An automated self-destruct command did not immediately destroy Starship. Instead, 40 seconds passed before the rocket finally exploded."

Personally I believe the ground-commanded destruct sequence failed completely.   The energetic materials were not placed to "blow rocket up" or, even less correctly, "detonate rocket".  They were placed to efficiently but reliably terminate thrust, and cut rocket into a few pieces that would slow down quickly and fall within the permitted impact area.  How could a firing event happen after 40 second delay?

I bet the rocket broke up and consequently exploded from structural loads, long after loss of control. (We were later told that an onboard fire on the Booster had broken connections to flight control computer.)    Speed, acceleration, and sideways and bending forces continued to increase as fuel mass decreased.  Posted videos show a sequence of two sudden outbursts of cloudy stuff.

Will now speculate that regulators gave Space-X a lot of grief, after the April flight, about the range safety failure.
Good thing the rocket didn't come down in one piece on Boca Chica town.
Maybe they turned up the design review by outsiders.  How about putting a button in the hands of a team that has done range safety at Cape Canaveral, Vandenberg, Wallops Island, etc for decades?  Not sharing any communication link or computer that's used for regular flight activity?

2
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!



3
Transformer (Iron Core) / Transformer costume for Halloween
« on: November 03, 2023, 11:23:54 PM »
A friend said he saw this picture on LinkedIn.
Little girl said she wanted to dress up for Halloween as a transformer. Perhaps thinking of the plastic toys by Hasbro that convert from cars to anthropomorphic action figures.
Here's what her dad came up with:

4
Capacitor Banks / A 63 volt electrolytic capacitor bank
« on: July 04, 2023, 05:34:03 PM »
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
/>
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).

5
April 16 will be the first flea market (aka hamfest, swapmeet) after a 3-year hiatus, not counting the false start in April, 2022.

The new venue is West Valley College in Saratoga.
Dates will be second Sundays instead of traditional second Saturdays.
Bumped to third Sunday this month because of Easter. I'm planning to be there with a space to sell and give things away.

https://www.electronicsfleamarket.com/

6
Light, Lasers and Optics / HV glows in incandescent lamps
« on: March 30, 2023, 08:18:26 PM »
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?

7
Electronic Circuits / Close look at overhead copper wires
« on: March 28, 2023, 10:29:08 PM »
Extreme weather a couple weeks ago interrupted electricity for 250,000 customers in my area.
Repair crews had hundreds of places to go fix things.   One of them left me and 150 neighbors in the dark for 60 hours.

High voltage overhead wires had broken and fallen to the ground.   
Early responders isolated a section of the grid, cut off dangling wires, and cleared the roads.


Cut-off wire was left coiled on the ground near the affected poles.  I cut three pieces as souvenirs, each including an end where wire had failed in tension. 

It's bare copper, diameter 0.163 inches (6 AWG), with patina from possible 70 years exposure to weather.   Pretty stiff, so I bet it's hard-drawn for strength instead of annealed for 1% better conductivity. 
All three wires have what looks like pitting corrosion near the broken end, but not elsewhere.   Did the corrosion make weak places?   Was it started by squirrel or rat teeth? Bird poop? Some ancient line-to-line arc event?  I guess any arcing between broken wires and earth would leave marks of a different color, and would most likely happen at a place other than broken end.   

It would be good to see if two of the broken ends are a complementary pair.

8
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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9
I might be able to get some free IGBT modules, of a type listed as obsolete.
MG12450WB-BN2MM.  Half bridge, 1200 V, 450 A. 
Date on datasheet is 2016.
https://www.mouser.com/datasheet/2/240/Littelfuse_Power_Semiconductor_IGBT_Module_MG12450-335994.pdf

Would those be a waste of time as a first IGBT project?  I'm not making a DRSSTC or interested in HV arcs for fun.
My application would be induction heating, or driving a Bennett x-ray tank unit (nominally 100 kHz) for powering a fusor.

A guess is that old and/or oversized IGBTs make the gate driver design more challenging than necessary. 

10
Light, Lasers and Optics / Institutional white LED's turning purple
« on: January 09, 2023, 06:45:45 PM »
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.

11
Near my work is a road where people sometimes leave unwieldy trash, to avoid a costly visit to the dump. This week a most unusual object appeared: a single-use bottle of high vacuum.

On closer inspection, it's a nominal 42 inch Trinitron CRT.   Weighs much more than 100 pounds. Has anyone here seen a bigger CRT television?
I bet it would float in water, neck-up. Might it serve as a sensitive hydrometer for some range of liquid density?   There is a rain-swollen creek not far away. :)

Tube was there on Tuesday and Thursday. Friday I went prepared to safely release the vacuum.  Somebody else had moved CRT onto the grass, and broken the neck off.
Obsessed with the buoyancy experiment, I got help loading float into car, then onto a pallet with aid of a forklift. 

Next week we can put it in a crate of water.   Any bets about whether it will sink, or how high and at what angle it will float?

By taking custody, it's now my responsibility to get the CRT to proper disposal site when experiment is over.  It will cost money.



12
Electronic Circuits / Resonant LCR with signal generator
« on: December 14, 2022, 05:01:38 AM »
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.

13
Electronic Circuits / Stepper motor drive without switching
« on: November 23, 2022, 10:23:07 PM »
The simplest and most common stepper motors, in my experience, have four wires and two stator coils.
Need to be driven with two bi-polar current or voltage sources in quadrature.

A suitable power source is another permanent-magnet stepper motor whose shaft is rotated.
In this example, manually turning the pinion on wide motor makes the worm-gear motor turn with exact speed ratio.
A poor man's selsyn motor set.


[edit] This set doesn't work backwards, even when worm shaft is spun at 1500 RPM with a drill motor.
Perhaps due to profound mismatch between the motors' electromechanical parameters?   The small motor does have a permanent magnet, so one can feel cogging when turning shaft by hand.

14
Light, Lasers and Optics / Non-laser pointer
« on: November 18, 2022, 10:05:29 AM »
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. 

.
.

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.

15
Laboratories, Equipment and Tools / A general purpose ballast adapter
« on: November 07, 2022, 07:29:33 PM »
This decades-old DIY power strip includes two receptacles wired in series.
Makes it easy to plug in a device under test, with current limited by another appliance such as a lamp or heater.
An alternative is to plug AC ammeter probes into slots of the second receptacle, to measure current in the device under test.

Dug it out in preparation for hot dog cooking measurement.
For practice, I ran it with a 3-way incandescent lamp holder on one side, and a two-speed food chopper on the other side.



16
Laboratories, Equipment and Tools / Electrical resistance cooking
« on: November 04, 2022, 07:38:54 PM »
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.

17
Light, Lasers and Optics / Laser pointer with no laser diode
« on: November 02, 2022, 02:36:11 AM »
Found this artifact during reorganization of storage boxes. It has a 1 milliwatt He-Ne laser inside.
Worked fine after years of idleness, without having to replace the two 9 volt batteries.

Unlike common laser diodes, this unit could serve as an inherently accurate wavelength reference.
Does anyone here know if laser diodes were common in laser printers and bar code scanners of the 1970's?

18
Laboratories, Equipment and Tools / Getting last joules out of batteries
« on: September 09, 2022, 07:24:33 PM »
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?


19
Electronic Circuits / Compact 90 volt lithium batteries
« on: August 25, 2022, 06:00:27 AM »
In the 1950's, hardware stores carried 90-volt "B batteries" for cordless radio sets. As a child in the 1960's, I got one "old stock" at a surplus store for my first neon glow-lamp experiments.   Now, as then, one could get the same voltage with ten "9 V" batteries snapped together in series.   It would be more compact to stack 30 lithium coin cells, rated for load currents up to a couple of milliamps.

Last night's experiment was prompted by discovery, in battery-waste bucket at work, of a plastic bag with about 100 used CR2032 cells.

It was sad but unsurprising that the cells were almost all completely dead, having been stored in a pile of metallic objects.   Two specimens had open circuit voltage around 2.7 V, which is what I'd expect from normally retired cells.   No other had more than 0.3 volts, and a few had reverse voltages!

I took the opportunity to try some insulating tubes for stacking.  Pictured tube is PVC irrigation pipe, nominal half-inch (0.840 OD).  Class 125 (the thinnest I've ever seen in hardware stores) has ID a little too small for CR2032's, before longitudinal slitting for a friction fit. Next time I'll make a tube by rolling glued paper or plastic sheet around a cylindrical mandrel.   Or put the slitted PVC over a mandrel larger than the cells, and heat it enough to remove internal stress.

My three 30-cell stacks had total voltages of about 1.5 , 1.0, and -0.8 V, diminishing second by second, while loaded with 10-megohm meter.

Didn't need to scrounge batteries.   One can get 100 brand-new CR2032's by mail for US $25 to $40.

20
Transformer (Iron Core) / Fatal accident using MOT
« on: May 25, 2022, 11:02:14 PM »
A few years ago, it became popular for woodworkers to burn fractal "Lichtenberg" figures into the surface, using MOT's.

https://www.woodfloorbusiness.com/installation/extraordinary-floors/article/15132850/frankenstein-flooring-from-an-idaho-floor-man
presents


Before long there were reports of electrocution, in the literal sense (fatal electric shock).
This unfortunate couple died, and later the electricity started a fire that burned down the workshop.
https://www.woodfloorbusiness.com/news/article/15291241/two-die-of-electrocution-after-fractal-wood-burning-accident

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March 21, 2024, 03:08:01 PM
post Re: [WTS] IGBT, Ferrite, Capacitors, Tools, PSU, Industrial components and parts
[Sell / Buy / Trade]
Mads Barnkob
March 21, 2024, 01:37:32 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Alberto
March 21, 2024, 11:42:07 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 21, 2024, 04:09:14 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 21, 2024, 02:15:31 AM
post My Homemade Structural Analysis X-Ray Machine
[X-ray]
Luca c.
March 21, 2024, 01:35:40 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 20, 2024, 10:40:00 PM
post Re: Difference between these transformers
[Transformer (Ferrite Core)]
Mads Barnkob
March 20, 2024, 08:03:41 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Mads Barnkob
March 20, 2024, 07:51:57 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 20, 2024, 10:39:47 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
March 20, 2024, 04:09:59 AM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 20, 2024, 01:13:23 AM
post Re: Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Keybored
March 20, 2024, 12:45:16 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 20, 2024, 12:30:30 AM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 11:12:24 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:47:49 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 19, 2024, 09:44:19 PM
post Phase Lead Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Saattvik24
March 19, 2024, 06:52:09 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
March 19, 2024, 05:02:44 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Mads Barnkob
March 19, 2024, 05:01:41 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 04:31:02 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
March 19, 2024, 03:59:54 PM
post Re: Benjamin's DRSSTC 2 in progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Benjamin Lockhart
March 19, 2024, 06:41:39 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
davekni
March 19, 2024, 04:05:49 AM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
OmGigaTron
March 18, 2024, 09:08:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 09:07:35 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
Twospoons
March 18, 2024, 08:57:06 PM
post Re: Can I Trust This Super Cheap Site?
[General Chat]
MRMILSTAR
March 18, 2024, 03:51:33 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:59:46 PM
post Re: 160mm DRSSTC II project | Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Late
March 18, 2024, 02:33:25 PM
post Can I Trust This Super Cheap Site?
[General Chat]
2020-Man
March 18, 2024, 11:02:12 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
Twospoons
March 18, 2024, 02:36:11 AM
post Re: Best forum for vacuum tube amplifiers?
[General Chat]
Mads Barnkob
March 17, 2024, 07:42:55 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 04:15:14 PM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Michelle_
March 17, 2024, 05:05:04 AM
post Re: Where's all this voltage coming from?
[Spark Gap Tesla Coils (SGTC)]
davekni
March 17, 2024, 04:50:51 AM
post Re: 2x Panasonic Inverter Microwaves - what to salvage, dangers?
[General Chat]
Twospoons
March 17, 2024, 04:45:17 AM

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