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Topics - profdc9

Pages: [1] 2 3
1
Electronic Circuits / Electronics projects I have been working on
« on: April 16, 2020, 03:50:40 AM »
I have built a standalone device for encryption called the ParanoiaBox.  You plug it into a TV and a keyboard, type messages, and you can encrypt them with AES 256 and EC25519 Diffie-Hellmann encryption.

https://github.com/profdc9/ParanoiaBox

There are literal screenshots of the television of the device at work.

Also I built a temperature controller to make a dry heat disinfection unit using incandescent light bulbs as a heat source.

https://github.com/profdc9/SimpleTempController

Also I made a Nixie clock which can be built using common components and IN-14 Russian Nixie tubes. 

https://github.com/profdc9/NixieClock

It has time, date, temperature, and humidity.  You can see a video of it at work:

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These projects are all through-hole for those who want some neat simple projects to build.   The Nixie clock and temperature controller uses an Arduino Nano V3 as the microcontroller and the ParanoiaBox uses a bluepill.  Something to play with while you are confined.

Dan

2
General Chat / Personal Protective Equipment reuse / Covid-19
« on: March 28, 2020, 10:20:04 AM »
In the USA (and I would imagine elsewhere) physicians use N95 respirators and other similar worldwide standards (see attached document) to prevent being infected while treating the infected.  Under ordinary circumstances, these respirators are designed to be discarded after use.  Because there is not an adequate supply to treat all of the anticipated infections, there are many ideas on how to disinfect and reuse these masks.   For example, look at

http://ppereuse.com
http://n95reuse.com

Personally, I have been working on methods of UV germicidal sterilization of these masks.  I wrote a document of how to create an ad-hoc UVGI sterilizer:

https://drive.google.com/open?id=1wF4yYgSE1n0Jqewb8JdwosTRhx0X89wF

Please spread the word about these resources to physicians that might need them.

One potential method of disinfection is ozone treatment.  Ozone (as well as nitric oxide and other nitrogen oxides) can be generated using a corona discharge.   Many of the above methods require specialized equipment or chemicals.  Perhaps a simple ozone disinfection device can be built from commonly available electronic parts that minimizes the risk of electric shock during construction and use. 

Another possibility is a device that can be used to heat enclosures to low temperatures safety, these temperatures being less than 150 C.  Look at the "dry heating" portion of this document:

https://docs.google.com/document/d/193mt42jUR8PxuONUY4A6YZsyOOmy6Psg6BDme3rjai8/edit#heading=h.h1qjojk7297y

Something like this Arduino temperature controller could be used to maintain the temperature of an enclosure at 60 C for an extended period, which is hot enough to cause accelerated degradation of the virus but not significant damage to the mask.

https://circuits4you.com/2016/06/06/arduino-temperature-controller/

Anyways, perhaps you can think of ideas on how to disinfected masks.


3
Hello folks,

After long last, a friend and I got together and we made music using a saxophone and a Tesla coil.  The saxophone has a piezo disc contact microphone which is connected to the interrupter I designed:

https://github.com/profdc9/DRSSTC-PCB-Pack/tree/master/interrupter

which then is connected to the driver

https://github.com/profdc9/DRSSTC-PCB-Pack/tree/master/ud29

The piezo disc is amplified by a JFET op-amp circuit powered by a 9 volt battery that connects to the interrupter sound input.   If anyone wants the details I can provide them.

Anyways, here's the videos of my friend playing the Tesla Sax:



/>
Enjoy!

Dan

4
Electronic Circuits / Talk on open source hardware in ham radio and KiCAD
« on: October 03, 2019, 03:52:54 PM »
I gave a talk on open source hardware in ham radio, and had a tutorial on using KiCAD to design PCBs as an example of open source hardware design.  You can download the talk from:

https://www.rars.org/documents/Open%20Source%20for%20Amateur%20Radio%20Projects_%202019_09.pdf

Enjoy!

Dan

5
Electronic Circuits / Version 2 of power supply
« on: August 27, 2019, 04:39:47 AM »
I am working on my version 2 of a linear power supply.  The first one worked fine, but I think I can do better.  The idea of it is to make it so that when you tear down and recycle the bits of old linear power supplies (the transformers and capacitors for example) you can reuse them with this new power supply PCB.  This design is a constant voltage (up to 30 volts) and/or constant current (perhaps up to 20 amps, depending on dissipated power).   This design uses very common op-amps (LM358) and up to four pass transistors in parallel (TO-220 TIP41C or 3055-type).

The new design has a few improvements, including a connection for analog or digital meter voltage and current outputs on the PCB, and provides 5 volts low current (< 50 mA) output for digital panel meters.  Also, a connection for an external analog control of the voltage and current if you want to use an Arduino to control the power supply. 


6
Electronic Circuits / Benchtop power supply PCB
« on: June 09, 2019, 04:28:29 PM »
I design a power supply PCB based on mixing the attributes of several designs floating around on the internet. You can find it at:

https://github.com/profdc9/LinearPS

The range is up to about 30 volts and the current with a single TIP3055 maximum is about 4 A, though if you run it at low voltage output and high voltage input, you probably want to use multiple TIP3055 to dissipate all that power.

It works. It is intended to take the output of a step-down AC transformer, and it provides constant voltage and constant current controls. It also provides sampled outputs of the actual voltage and current output to connect panel meters, and a low current (zener) +5V to supply digital LCD meters. It can be adjusted for different input AC voltages and different ranges of output voltages and currents using trimmers. Also, it can have up to four TO-220 output devices that can be mounted to a common heatsink (for example, TIP41C or TIP3055 devices) to achieve higher output current.

I made this so that old junk and surplus transformers can be turned into useful benchtop power supplies.

DC can also be input into the board, but the minimum limiting output current will be around 500 mA.

Dan


7
Solid State Tesla Coils (SSTC) / Flat Secondary Coil on PCB?
« on: May 01, 2019, 05:54:26 PM »
I was thinking about designing a small kit-based Tesla coil where rather than the seconary coil being a solenoid, it is a flat spiral.  Of course the secondary inductance goes down, but is there any reason this shouldn't work?  Flat spirals are already used for resonant power transfer applications (e.g. wireless charging and induction cookers).

The board I designed has (I calculate) about 1 mH of inductance.  It is about 150 turns of 0.13 mm wide traces separated by 0.15 mm.  This is the thinnest I could fit in the design rules of the process.

Anyways I was up late last night and drew up a PCB.  The hole in the middle is for a post to put the topload on sticking up from the PCB.  The hole on the edge is to connect the ground.  There is a six turn coil on the back that is used to sense the current in the secondary for feedback purposes.

I was thinking too that I could stack the boards to get more turns and place a thick HDPE insulator between them.    The center of each coil would be connected to the ground of the next in series, and these would be stacked as to be placed over the primary coil  so that the board would intersect  the magnetic field lines of the primary coil.

Here is what I drew up last night:



Any comments about this design?  I want to call it the "Conversation Piece" which would be a little tabletop SSTC coil.  It would be powered by 12-30 VAC.

Dan

8
You can find the git project at

https://github.com/profdc9/VNA

What is a vector network analyzer? It is a tool for measuring impedance, reflection, and transmission.  The one I designed works on one port from about 30 kHz to 470 MHz, and on two ports from about 300 kHz to 470 MHz (though I have not tested transmission that much this high).

How does it work?  You connect a short, open, and 50 ohm load to the transmit port to calibrate the reflection, and then connect the transmit to to receive port to calibrate the transmission.  Then you can connect a load to either the transmit port, or from the transmit to the receive port, and get its impedance or transmission/reflection characteristics.

What can this do for coilers?  You could connect it to your coil and directly measure the impedance of your coil.  For example, if your system has multiple resonances, you can sweep them with very fine frequency resolution and see the upper and lower frequencies.  You can also directly measure the "Q" of your coil for example.  Basically it can measure impedances between about 2 and 10000 ohms at RF frequencies.

Does it cost a lot?  Probably about $40 in parts or so to build.  I tried to make it as easy as possible, it uses mostly through-hole parts but one surface mount part.  It even has a touchscreen.  I designed it mostly for ham radio use at HF/VHF, but it should be useful down to 30 kHz.  To be more usable at lower frequencies, it is best to put a slightly bigger common-mode choke onto it, which will make the minimum frequency lower at the expense at somewhat reducing the maximum frequency because of parasitic effects between the turns in the choke.  But even with a bigger choke it should be usable at least to 200 MHz I think.  Here's some pictures of it in action.







You can also hook it to USB and looks like a USB serial device and you can type commands at it to get data off of it.

Anyways, I know this is not high voltage, but it could be useful for high frequency circuits in high voltage.

Dan


9
General Chat / Hallloowweeen
« on: November 01, 2018, 04:19:50 AM »
Hello,

I just wanted to mention that tonight I set up my Tesla coil and it was a big hit with the kids in the neighborhood.  Nothing excites the trick-or-treaters like a musical lightning machine on Halloween.  I played Hall of the Mountain King, Night on Bald Mountain, Toccata and Fugue, Funeral March of the Marionettes, as well as other tunes.

Dan

10
Hello,

I made a theremin based on a STM32 microcontroller (the $3 bluepill).  You can see me play it in this video

/>
The theremin as you can see is quite sensitive.  I actually put a fiber optic output on the board so I can program it to be an interrupter for a DRSSTC.

The parts are very inexpensive and the circuit is fairly simple.  The PCB, schematics, and the software are on a github

https://github.com/profdc9/MCTheremin

If you want to try to build it let me know.  Enjoy!

Dan



11
I have more music that I made two note:

"Personal Jesus" by Depeche Mode
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"Dreaming" by Depeche Mode
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"The Pink Panther" by Henry Mancini
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"Fanfare for the Common Man" by Aaron Copland and Emerson, Lake, and Palmer
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"A Little Respect" by Erasure
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A zip file with the Midi's are attached.

Dan

12
I use the 2N7000 N-channel small signal MOSFET for many projects because it is convenient and dirt cheap, often available for as little as $0.05 USD a piece.  However, I have never found a similarly cheap, available P-channel MOSFET.  I have used the BS250 but it costs ten times as much as the 2N7000.   Are there any other P-channel through-hole small signal MOSFETs available that can be obtained at a similar price to the 2N7000?  I think through-hole MOSFETs are difficult to get in general but they do exist.  Otherwise I'll stick to using the 2N2907/2N3906 BJTs for projects, but it would be handy to have a P and N channel MOSFET for complementary pairs.  Another option is just using an inverter like a CD4069 biased into its linear region perhaps?

Thanks,

Dan

13
Dual Resonant Solid State Tesla coils (DRSSTC) / New Tesla Coil songs
« on: June 16, 2018, 03:38:50 AM »


Master and Servant by Depeche Mode

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Cult of Personality by In Living Colour

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The Blue Danube by Johann Strauss Jr

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Chopin Waltz, Op 18 Eb minor

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Partita 3, Gavotte en Rondeau by Bach

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In the Hall of the Mountain King by Grieg

/>
The archive with the MIDI files is included.

Dan

14
I would like a way to turn any instrument into a Tesla Coil instrument.  So I am using a piezo disc as a contact microphone on my acoustic guitar, and amplifying this with a JFET op-amp (LF351).  Obviously very noisy and distorted.  I think it might sound better with horns or woodwind instruments.

Here's a video of me playing my guitar and the lightning issuing forth:

/>
Also, I have a demonstration of the AC-line interrupter which is an attempt to improve the duty cycle of DRSSTC Tesla Coils by interrupting only during the peak of the AC cycle.   I need to place a voltage and current meter on the line to check the power factor to see if the interrupting on the peak improves the power factor, but I made a video of it in action.  It makes a nice growl like an asynchronous spark gap tesla coil makes.

/>
Dan

15
Electronic Circuits / OpenTheremin v3 for Tesla Coil
« on: May 29, 2018, 07:01:20 PM »
So I built my theremin and while it works, it is not the greatest.  As predicted, the RC-based theremin is a good noisemaker but is hard to control.

So instead, I am going to modify OpenTheremin v3 to directly be an interrupter.  I laid out the board for thru-hole, which I have attached.  A picture of the board is here:



Since there are no thru-hole varactors anymore as far as I can tell, I used four 1N4001 in parallel which roughly has the same capacitance as the varactors used in the OpenTheremin (BB914).

I also got rid of the Arduino and just put the Atmega328 on the board itself, as well as the power supply, so it is self contained, and I added a circuit to output the MIDI.

Dan

16
I have some more songs for you.  Tesla coil music is awesome and very noisy.

"The Spirit of Radio" by Rush

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"Here Comes The Sun" By The Beatles

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"Classical Gas" by Mason Williams

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"War Pigs" by Black Sabbath (7 minutes long).  Yes I am headbanging.

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"Night on Bald Mountain" by Modes Mussorgsky (10 minutes long!)
I turned the power down a little to make sure it would make it through all the way without the breaker tripping.  There are a few times where the coil can't hit the high notes.

/>
The midi files I've done so far are attached.

Dan

17
Hello,

I am releasing the DRSSTC PCB pack.  This includes the UD2.9 skip pulse gerbers, as well as PCBs for interrupters and bridge boards.  These boards are all less than 10 by 10 cm and so can be made for $5 from many PCB houses (not including shipping).  If you get many boards made at once, you can spread the cost of the shipping over these boards.

Boards included:

1)   UD2.9 skip pulse
2)   UD2.7 conventional board (without skip pulse)
3)   UD3.1 that uses the PSoC5 CYC8KIT
4)   Half Bridge with 2 transistors and a place for a capacitive divider for the other side of the bridge, and a place for RC snubbers on each transistor
5)   Half Bridge with 8 transistors (4 on each LO/HI side)
6)   Full bridge with 4 transistors and a place for RC snubbers on each transistor
7)   Full Bridge with 8 transistors (2 on each LO/HI side, two half bridges)
8)   Burst interrupter with external triggering
9)   AC line interrupter, includes a spot for the ATTINY85 to implement the OneTesla tiny USB interrupter.

These are all made with kicad, so you can modify them as you need to (kicad is open source software).

Dan

18
I have a full-bridge of IGBTs with 2 IGBTs paralleled in each part of the bridge.

While running the coil, it seems like only two of the eight transistors is damaged.  The other six seem like they're ok, which I established by the crude method of testing to see if the emitter-collector connection is shorted.

Is it safe to reuse the six transistors, or should I toss the six good transistors and get eight new ones?  I think the two transistors that were blown are the two on each side of the half bridge that the bus power shorted through.

Also, can I use a heat gun to remove the supposedly still good transistors from the bottom side of the board?  They are soldered in the TO-247 sockets, or will this damage the transistors too much?

Thanks,

Dan

19
Hello,

I managed to modify and flash the digispark with the oneTesla interrupter code.   Here's how to do it:

1.  Buy a Digispark (usually $5 to $10).
2.  Get an Arduino Uno to use as a programmer.
3.  Follow these instructions to plug in the Arduino as the ArduinoISP avrisp programmer:

http://www.instructables.com/id/How-to-Program-an-ATtiny-85-Digispark/

In particular, connect the following pins together

Uno 5V : Digispark Terminal VCC
Uno GND:  Digispark Terminal GND
Uno pin 13:  Digispark P2
Uno pin 12:  Digispark P1
Uno pin 11:  Digispark P0
Uno pin 10:  Digispark P5

4.  Install Arduino software to get avrdude

5.  Flash the Digispark with new code:
avrdude -C"C:\Program Files (x86)\Arduino\hardware\tools\avr\etc\avrdude.conf" -v -pattiny85 -cavrisp -PCOM5 -b19200 -D -e -Uflash:w:main.hex:i make

using the main.hex file from the attached distribution, change the paths and the com port to match your configuration.

6.  Disconnect and plug in the digispark; it should be recognized as a OneTesla MIDI controller.

A single pole-single throw switch is attached to P0, the LED is attached to P2 through a 100 ohm resistor.

Dan


20
Hello,

I am working on a new version of the Universal Driver called UD2.9, which includes the pulse skip ability.  By closing a jumper, pulse skip functionality is active, otherwise the standard overcurrent detection is active.  I also added an external disable feature for adding, for example, thermal shutoff.

I have assembled and bench tested it, so far so good. :)  Here's a picture of the assembled board:



Hope to put this in the coil soon and not have blown IGBTs!

Dan

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