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Topics - profdc9

Pages: [1] 2 3
1
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

2
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. 


3
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


4
Solid state Tesla coils / 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

5
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


6
General chatting / 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

7
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



8
Dual Resonant Solid State Tesla coils / More Tesla Coil Music
« on: July 08, 2018, 03:15:36 AM »
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
/>
"A Little Respect" by Erasure
/>
A zip file with the Midi's are attached.

Dan

9
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

10
Dual Resonant Solid State Tesla coils / 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

/>
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

/>
In the Hall of the Mountain King by Grieg

/>
The archive with the MIDI files is included.

Dan

11
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

12
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

13
I have some more songs for you.  Tesla coil music is awesome and very noisy.

"The Spirit of Radio" by Rush

/>
"Here Comes The Sun" By The Beatles

/>
"Classical Gas" by Mason Williams

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

/>
"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

14
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

15
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

16
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


17
Dual Resonant Solid State Tesla coils / UD2.9 skip pulse assembled
« on: May 08, 2018, 04:20:55 AM »
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

18
Hello,

I have added to the interrupter I am working on the following capabilities

-  Regular adjustable frequency and pulse width interrupter
-  Ability to interrupt on only the peak of the AC cycle, an experimental feature to try to improve power factor
-  External sound trigger to play sound from an audio source and interrupt, with an adjustable pulse width
-  Added the OneTesla ATTINY85 USB MIDI interrupter as well, which shares the same LED

So I think this should be a useful all around interrupter for playing both from analog and MIDI sources and to test with.



Dan

19
Dual Resonant Solid State Tesla coils / Mains voltage interrupter
« on: May 01, 2018, 03:15:44 PM »
Hello,

Last night I modified the burst mode interrupter to interrupt off of the peaks of the AC cycle.  The idea is to improve the power factor of DRSSTC by only drawing current from the mains during the peaks of the AC cycle so that any bus capacitors are not discharged during the troughs of the AC voltage, reducing the inrush of current into the capacitors at the beginning of the peaks.  This should hopefully improve the power factor with minimal difficulty or expense.  An AC transformer adapter as both the source of power and the signal to interrupt from.  A control voltage sets the level over which the interrupter is allowed to operate.  There is a provision for an external control of the interrupter signal as well.

I won't get around to trying it for a little while but I'd be happy to share the PCB with anyone who wants to try it sooner than I will.

Here is a diagram of the PCB:



The schematic is attached.

Dan

20
I placed a metal box around the driver circuit.  The coil is now much better behaved and can produce power with a low BPS.  So the lesson is, place your Tesla coil driver circuit in a metal box, and I also put little chokes on the transformers and the DC power supply going into the box.

Here's the video at low and medium BPS.

/>
Dan



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