After transitioning to WordPress, I started writing up my newer projects as ‘blog posts’ rather than ‘pages’. Please find below a list of links to every electronics project related blog post:
- Overclocking the pi4 with the Blink Blink ICE Tower CPU Cooling Fan
- Supercapacitor Uninterruptable Power Supply (UPS) for Raspberry Pi
- The Hayes Chronograph, a Remake for 2020
- Tandy 1000 Upgrades / PS2-Tandy Keyboard Adapter
- Restoring a Convergent Technologies NGEN PC/Workstation (Burroughs B25 / Unisys)
- Raspberry Pi Controlled DC Load
- Hot Shoe to 1/4-20 Quick Release Magnetic Mount for LumeCube
- Building a Power-over-Ethernet (PoE) Power supply using a DPS5005 module
- Scott’s FrankenNUC: 10Gbe Fiber Network on a 5th Generation Intel NUC 5i7RYH
- RAIN: Redundant Arrays of (In)expensive NUCs
- DIY Wireless Temp/Humid/Pressure sensors with Raspberry Pi Receiver, for monitoring stored 3D printer Filament
- Raspberry Pi 4: Do you need a fan? What’s the best fan for a raspberry pi 4?
- Vacuum Fluorescent Display (VFD) on a Prusa I3 Mk3 Printer
- The Nixie Tube Filadometer – A Nixie Tube Filament Meter for your 3D Printer
- COB LED Panels: 10 watt, 70 watt, and 200 watt.
- Resistive Load, Constant-Current Power Supplies, and a 3D Printed Desk Lamp
- 3D Printer OctoPrint Monitoring with Prometheus and Grafana
- Raspberry pi based indoor air quality monitor
- Building the ultimate USB power distribution system
- Making the e-paper equivalent of an Etch-a-Sketch
- Yet Another Masterplay Clone
- Atari 5200 Playstation 2 Dual-shock controller adapter
- Homemade Atari 5200 Analog Controller
- Scott’s Z80SBC: Z80 Single Board Computer
- Pi-Powered Atari 5200 Multi-ROM Cartridge (MultiCart)
- Raspberry Pi Virtual Floppy for ISA (PC XT/AT) Computers
- Converting a Seeburg 3WA Wallbox into a Remote for a Modern Music Player
- 8-bit ISA DiskOnChip / RTC board
- Measuring USB Power Cable Voltage Drop with my DC Load
- Leia’s LED Clock
- Building a Micro 8088 Single Board Computer
- 8-Bit ISA EMS Board / Flash Disk Board
- PS2-TTLSerial Adapter for RC2014 and MIDI
- Raspberry Pi Midi Hat / Building a Raspberry Pi Midi Jukebox
- Vintage MIDI: Roland MT-32, Roland SC-55, HardMPU, and an Xi 8088
- CTS256A-AL2 Text-To-Speech Board
- ISA Speech Synthesizer board using SP0256A-AL2
- Z80 Retrocomputing 18 – Z180 CPU Board for RC2014
- Z80 Retrocomputing 17: Enhanced Z80 CPU Board for RC2014
- Building an Xi 8088 PC
- Z80 Retrocomputing 16 – Unix on RC2014
- Z80 Retrocomputing 15 – CP/M on RC2014 Revisted, Using RomWBW
- Qume 842 8″ floppy drive with a RC2014 Z80 retrocomputer
- Building a Zeta V2 Single Board Computer
- Z80 Retrocomputing Part 14 – RC2014 Floppy Controller Boards
- Z80 Retrocomputing 13 – RC2014 VFD Display Board
- Z80 Retrocomputing 12 – Talking Nixie Tube Clock
- Z80 Power-on reset circuits
- Z80 retrocomputing 11 – CP/M on the RC2014
- Z80 Retrocomputing 10 – RC2014 CompactFlash board
- Nixie Calculator Update – PCB availability, source code, design notes
- Z80 Retrocomputing 9 – CTC and dual serial ports for RC2014
- Z80 Retrocomputing 8 – Speech Synthesizer for RC2014
- SP0256A-AL2 speech synthesizer chips: Genuine vs Counterfeit.
- Z80 Retrocomputing 7 – RC2014 DAC (Digital To Analog Converter)
- Z80 Retrocomputing 6 – RC2014 TIL311 Front Panel Board
- Z80 Retrocomputing 5 – Single Stepper for RC2014
- Z80 Retrocomputing 4 – Bus Supervisor
- Z80 Retrocomputing 3 – Bus Monitor Board
- Z80 Retrocomputing 2 – Real Time Clock for the RC2014
- Intro to Z80 Retrocomputing
- Building the Dutchtronix Scope Clock
- Product Reviews: Mooshimeter, Raspberry Pi Black Slices Case, Powerhorse Surface Cleaner
- Magic Eye Tube Audio Spectrum Analyzer
- Magic Eye Tube PC Monitor
- Magic Eye Tube interfacing with a Raspberry Pi
- DIY Nixie Tube Frequency Counter
- Raspberry Pi Switching Power Supply Shield
- Eico 430 Oscilloscope
- Sparkfun third hand kit – review and modifications
- Aoyue 128 Soldering Tip Polisher Review
- Eico 369 RF Sweep Generator
- DIY Digital RF Attenuator
- Sinometer VC2000 Frequency Counter Review
- RGB Rotary Encoder on a Raspberry Pi
- Polaroid 312 LED Camera Light – Teardown and Repair
- DIY Variable AC Power Supply
- Pilotuner T601 FM Tube Tuner Restoration
- Hantek T3100 scope probes unboxing and review
- Ebay VCO module evaluation
- LM2576 constant voltage / constant current switching power supply
- DIY RF Signal Generator
- Learning to use the GALI-55 MMIC
- My new KG-650 RF Signal Generator
- Creating the ultimate home automation keypad
- Interfacing a VFD display to the raspberry pi
- GE iTwinkle 36 LED Christmas light teardown and hacking
- Raspberry Pi Powered Individually Addressable Christmas Lights
- Nixie Tube Calculator, Powered by a Raspberry Pi
- Raspberry Pi Nixie Tube Clock Prototype
- A temperature and humidity probe for the Elk M1 Gold
- Cooper Wiring Devices TR7735W-BOX night light teardown
- Propeller-powered IN-12 Nixie Clock
- Nixie Tube Web Counter
- Scott’s iPad digital audio optical receiver / amplifier
- Interfacing Dekatron Tubes to a Microcontroller
- The Packetron 9000
- Auto-dimming Chumby hack
- High voltage power supply
- Plasma Speaker
I developed my first add-on board for the RC2014. This board is a real-time clock and an 8-bit output port. I'll use it to build a Nixie Tube Clock.
This is the first in my series of Z80 retrocomputing blog posts. It serves as an introduction. I started by building the RC2014, a popular retrocomputer platform that I found on Tindie.
In this post, I put together a magic eye tube spectrum analyzer using my two-tube boards, op-amp boards, and a spectrum analyzer board that uses the BA3830S chip.
I thought it would be cool to use magic eye tubes to visualize the activity on my PC, so I threw together a two-tube project that shows CPU utilization and network utilization.
I discovered magic eye tubes on eBay. I bought a couple of cheap and simple boards and assembled them. Then I tried to see what it would take to control the tubes from a Raspberry Pi.
I've always wanted a Nixie Tube Frequency Counter, but one has never come up on eBay for a price that I was willing to pay. So I just made my own using the same Nixie Tube boards as the calculator project. I learned a bit about frequency counter front-ends in the process.
There are many times when I want to power one of my Raspberry Pi projects from 12V instead of 5V. I built this switching power supply shield to make it easy to do so.
I bought an Eico 430 Oscilloscope, an old analog scope from the late 50s / early 60s. It's a cathode ray tube scope, with vacuum tubes used throughout. It works amazingly well given its age, and will actually be a useful addition to the bench.
I've always wanted the Sparkfun third hand kit, ever since I saw it in their new products page. I finally bought one, and this post contains my review, as well as some modifications.
The Aoyue 128 is a soldering tip cleaner. It has two rotating brass brushes that clean and polish your soldering iron type. I bought it on a whim, and review it in this post.
I bought an Eico 369 RF Sweep Generator. The video covers my experiences with it, from the moment I unboxed it to when I made the first sweep.
I build a digital RF stepped attenuator. It uses a PE4302 chip, along with an RGB encoder and a VFD display. It attenuates from 0 to 31.5dB in 0.5dB steps.
I review the Sinometer VC2000 Frequency Counter. You can buy one on Amazon for less than a hundred bucks.
The video in this blog entry shows how to connect a rotary encoder to the Raspberry Pi. The particular encoder is from SparkFun and contains a pushbutton switch as well as a tri-color LED.
People may have noticed my Camera Light shut down unexpectedly during the Pilotuner video. I finally got around to tearing the camera light apart and fixing it.
I build a 0-30V adjustable AC power supply for the bench using a Variac, 28 VAC transformer, a digital panel meter, and a handful of other support components.
I restore a Pilotuner T601 FM tuner. This is an interesting piece of history, as it's one of the earliest FM tuners. It doesn't even have an amplifier and is designed to be attached to an existing radio or receiver.
I evaluate some Hantek T3100 oscilloscope probes. These are x100 probes, that I bought for using on high-voltage projects, such as tube radios.
I ordered some cheap VCO modules from eBay. Only $20, using an MC1648 VCO oscillator chip, and they work from 70Mhz to 200Mhz.
I design an adjustable voltage / adjustable current limit power supply using an LM2576 buck converter. For the current limit function, I use an op-amp to measure the current from a sense resistor, a second op-amp to compare that to a pot, and then feed that signal back into the feedback pin.
I build an RF signal generator from an article in Nuts and Volts. I learned many things about RF circuits during this project, and the blog post details some of the lessons.
I didn't know what the heck I was doing when I tried to use a GALI-55 MMIC in my RF signal generator. A few basic mistakes led to hours of diagnosing the problem.
I bought an old tube RF generator on eBay. It works surprising well considering the age of the technology. I use my Rigol scope to view some of the waveforms and play with the RF generator a bit.
I wanted a control center mounted to my monitor that I could use for important home automation functions. I build some custom keypads using Cherry MX blue keyswitches and interface them to a Raspberry Pi. I add a VFD display for status info.
I interface a vacuum fluorescent display to a Raspberry Pi.
The availability of GE35 color effects sets, the ones that have been hacked since 2010, is poor. In this article I tear apart one of the new iTwinkle sets to see if they are compatible with the same hack.
GE G35 Christmas bulbs are easily hackable. I wanted to control them with my Raspberry Pi, and this describes how I used a Parallax Propeller to do the intermediate protocol handling.
My latest Nixie Tube Project, a desktop calculator controlled by the Raspberry Pi. It's currently on Kickstarter!
Nixie tube clock prototype using IN-12 Nixie tubes with a Raspberry PI. 74141 / K155D drivers are used with 74HCT595 shift registers.
I design and build a temperature and humidity probe for the Elk M1 Gold Alarm / Home automation panel. A parallax propeller microcontroller and an SHT11 sensor is used.
A futile attempt to tear apart an LED night light in order to alter the sensitivity of the photocell.
My first self-designed Nixie Tube clock prototype. I use IN-12 Nixie tubes along with a parallax propeller microcontroller and a UP501 GPS module.
I design a hit counter for smbaker.com using a Nixie Tube display module and a parallax propeller microcontroller.
Unhappy with existing receiver options, I decided to build my own digital-audio receiver. I used IN-13 nixie bar graphs, a MiniDSP/MiniAmp stack, and an airport express. I even added an Alps MotorPot controller by a parallax propeller microcontroller so the volume can be changed from a web browser. Eventually modified this project to play Pandora using a raspberry pi.
Everything you ever wanted to know about interfacing an old soviet dekatron tube to a microcontroller. I use a parallax propeller and some MPSA42 transistors.
My favorite dekatron project. Using a parallax propeller to query my cisco router, I visualize my Internet throughput using old Russian dekatron tubes.
While my chumby has long since died, this page describes my efforts to modify it to add automatic dimming, because the thing was just too damn bright at night.
This is the high-voltage power supply that I use to power my dekatron, nixie tube, and geiger counter projects.
My efforts to construct a plasma speaker, which is basically an electronic arc modulated by a sound source. It all started from an Instructables article I found on the web, and there were several misadventures as I tried to turn it into a workable design.
Scott
Very good work you did here! The IRF250 you got is way better then my already very expensive in Brazil 540. And very clean PCB. Mine home-made board blew some traces so…
About the MOV: I think you really don’t need them if the system is well tunned. The problem is that while you are tuning it the FETs blown one after another… If it is tunned a 110 V MOV should not heat too much. Same to the snubber resistors. Mine smoke several times.. but at least the mosfet was happy.
Do you have a oscilloscope available to tune your system? It helps a lot with frequency modulation!
Good to know that I on google! hehe
Best regards and good luck with your project
Tobias
Thanks very much for all the comments, Tobias. I found your site very helpful in my research. The snubber resistors aren’t getting hot yet, but I do have two 5-watt resistors in parallel, so that’s probably giving some pretty power handling capacity.
I too have blown many mosfets while working on this project. Most of them were IRF840s or IRF540s. That’s why I decided to try out the IRFP250. The current board I created is actually setup so that either mosfet can be soldered in place.
I do have an oscilloscope available, but I’ve not yet figured out the procedure for frequency tuning. Any tips you can provide would be helpful.
This picture shows the voltage on the primary while I was tuning the system:
http://tobiasmugge.files.wordpress.com/2009/03/p250509_09-55.jpg
That’s the best I’ve got but can be tuned better.
Are you using a cap in parallel with the primary on the flyback?
It’s difficult to choose the value because you have this capacitance, the number of turns on the primary, the frequency and the dead-time to adjust.
Fix the dead-time around 40% and start from there. Change capacitance, search for the best frequency. The right one is when the arc is not that hot but consistent and the current consumption is low. You want to work something between 60 and 100 kHz. More frequency equal better sound.
If the freq is too high or to low just change capacitance or turns. But stay around 12 turns for 30 V. And start tuning with a low voltage, like 12 V.
To fine-tune change the freq and dead-time until the wave of the voltage on primary reaches the ‘smoothest’ point.
Yes, it takes a loot of time!
Hello Tobias, I don’t have a capacitor in parallel yet. Are you just doing that for tuning, or for general operation as well?
I haven’t got the scope out yet, but I was playing with the circuit tonight and tuned it to what sounded best. I’m now getting somewhere around 4 amps at 30 volts. I still ended up burning out the mosfet after a while of continuous operation (I’m thinking the CPU fan I have is not adequate enough for extended operation).
There’s something a little weird with starting the arc at my current tuning. To “start” the arc, I have to close the gap down to about 3/4″. Once it’s started arcing, I can easily open it to 2-2.5 inches or more.
Got the oscilloscope out and made some measurements…. they’ve been added to the post. Not entirely sure what I’m looking for at this point. I haven’t added a cap to the primary yet.
I used Richie’s site as one of my references. From there Ive got the snubber design. You want to reach the Vc waveform:
http://www.richieburnett.co.uk/temp/flyback.gif
Mine is pretty close as you can see on the picture of my site.
That waveform gives me a 1″ starting arc. I did not tried to stretch it up.
With 30 V, only ~2A. Depending on the modulation, 2.6A. And no burning fets.
The cap stays there for operation!
Best luck
Very interesting results. I started playing with capacitors. The first few I tried (2.2uf and 1uf respectively) increased the amperage significantly. However, when I got to the lower values in the parts bin, that’s where things got interesting. An 0.047uf/250V cap reduced the current draw by about an amp, but the little cap started to get quite hot. I started playing with some 0.01uf/1.6KV caps and found that with two of them in parallel I was able to increase the frequency to about 120Khz, dropping the current draw to about 2 amps. Four of them in parallel drops the current to around 1.6A, but I’m tapped out as far as I can go on the pots for lowering the frequency.
I finally have a COOL running plasma speaker that sounds pretty good. As far as I can tell no more fried mosfets or hot MOVs.
Time to start work on revision 2.1 of the driver board…
Very good results!
Good to know that you did it.
Are you in USA? It’s quite easy to you to buy FKP caps out there.. Those does not get hot.
Maybe we can help each other designing this rev2 board? Tell me how many bucks it costs to make a industrial board there.. Here in brazil it’s like $60.. a little fortune! hehehe
A tip: the PWM signal circuit cant be close to the power section of the board. Take a look on yours. It’s pretty close. This lead to noise…
Yes, I’m in the US. Some of the capacitors I have laying around are Wima caps (from Mouser, I think). I’m not sure about these particular 0.01uf/1600v ones though. I’ll have to double-check where they came from.
Generally I get the pc-board from batchpcb. The cost to make the last board was only about $17, but one has to add $15 shipping and handling to that. I usually batch up several different projects together so I can save on the shipping and handling fees, so it’ll probably be a while before I submit the next plasma revision. The new design is already slightly bigger, and batchpcb charges by the square inch, so it’ll cost a bit more. I have moved some parts around a little bit. In particular, the op-amp is no longer next to the high power section and has been moved to the other side of the TL494 where the rest of the low power stuff is. I’ll see if I can post an image of the revision when I get a chance.
I’m thinking of modifying the design to a push-pull design (or at least have the option of doing it). I don’t think this would be hard to do — it’s basically duplicating everything on pin #10 of the TL494, sticking it on pin #9, and switching the output control jumper. Then we put a center-tapped coil on the flyback. I’m assuming I would duplicate the snubber as well. This could all end up a much larger board which is a little unfortunate. I might try some experiments first to see how much better the push-pull design works.
In my next plasma speaker project I would like to get rid of that 4429 IC to try a GDT.
494 -> BC transistor -> GDT -> FET
And go for bigger FETs as you did.
The problem is that here in Brazil anything unusual is too hard or to expensive to get. Or even both. The 4429 is both.
Are you trying to do a halfbridge design?
No, I’m going to try experimenting with a push-pull design… If I understand correctly, this is different that a half-bridge. Whereas the half-bridge is switching a single primary between +V and -V, a push-pull uses a center tapped coil, with +V at the center and alternately switches either end to -V. The design was suggested to me in one of the comments to my youtube video, so I’m going to give it a shot. Of course, my knowledge of switching supplies is very limited, so I may not be understanding correctly. 🙂
Anyhow, I sat down to look at my schematics tonight, and before I knew what happened, I had a design ready and sent off to batchpcb. Should have the new board in a couple of weeks (batchpcb is rather slow). It’s easy to get carried away when one sits down with the schematic software…
As far as the TC4429s, I got them from digikey at about $1.72 each. Seems like I shopped around to get a good price on them, but unfortunately I only grabbed a limited quantity (didn’t know at the time my summer free time was going to be dominated by plasma speaker projects!).
I thought I would write you and tell you how much I appreciate you sharing you experience and your design. Few people on the internet have shared a complete Schematic. I look forward to seeing a video of you new push pull design.
I hope I can purchase a PCB from you when you are satisfied with your design.
From your comments to Tobias your explanation of how the a push pull works sounds correct to me. I would very much like to follow along with you during your design adventure. I am no expert but I am well read and I have resources that may be helpful along the way.
Feel Free To E-Mail me
Good Luck.
Could you explain you preference of FM over PWM, please?
Thanks for the comments, Peter, and thanks for setting me in the direction of the push-pull design. I’m looking forward to seeing how it compares to the current design. We should know in about 2.5 weeks! 🙂
As far as the Pc-boards, I use batchpcb, and they have a marketplace. I’ve held off on listing them publicly so far until the design(s) are finalized, but once they’re ready I’ll definitely list them so that people can order a board. Processing from batchpcb takes a little while, but getting a quality double-sided silkscreened and solder-masked board is worth the wait.
As far as FM vs PWM, I thought the FM sounded better. The board is designed to support either method (in fact, you can even use both at the same time; it would be interesting to feed two different audio sources and see what happens). The latest revision will have the option of jumpering the op-amp to either. As far as why the op-amp is there, it came from tobias’ design…
Thanks again for the comments!
You need that op-amp to have a high impedance audio in. It works together with the capacitor that follows. This last one changes the reference from 0 V to 6 V to source the TL494. Connecting a capacitor this way ensures that no DC voltage differential will be created between the op-amp and the tl494. Only pulses pass throw the cap.
When you read on the net that people blew some audio players off experimenting with plasma speakers that’s because they did not use a high impedance audio in =)
The finest plasma speaker circuit I’ve ever seen. If possible, can you please also publish your PCB design?
I was planning on holding off putting the PCB pattern up (and the link to manufactured boards at batchpcb) until the next revision is done as there are a few important changes I made. I definitely will do so when the new boards arrive, thanks for the comment!
Thank you, I’m looking forward to it. My biggest problem is FETs’ heat dissipation; I’m thinking about how to absolutely avoid linear mode, maybe with an additional switching-mode FET driver. This is only a plan, I haven’t tried that yet.
I can’t wait to see your new board. The suspense is killing me. I would really like to know what you thoughts are on the Push Pull system. I already started ordering the parts for your board when you make it publicly available. May be a quick up date would be nice. Thanks and keep up the good work!
great info! very impressive work!
I and every one else following you would appreciate an up date on how the new push pull boards are going. Thanks. 🙂
Any updates to the schematic? I have been looking over the parts, and getting setup to make one for myself. I have also been wondering if the input audio can raise and lower the volume of the “speaker”?
Can’t wait to see the next revision! Out of all the system’s I’ve looked at this seems one of the best designed
How is it going. Are you blasting some matalica on your new plasma speaker yet. LOL . An up date on you web site once in a while would be nice. Thanks and keep up the good work.
Peter
Do you think a 163 volt clamp 80 volt DC rated MOV will work. I am building my own prototype and need advice on picking a MOV. Any Advice would be help full. Thanks.
Hello ther thank you for your post, i have been searching for plasma speaker and i did like very much yours, i wounder if you mind to send me the list of materials necessarie to do the entire build. Thank you so much
Ty for the prints, i was searching for a good FM build and these fit the bill brilliantly. http://hv-labs.xf.cz/images/singarc/budic-mustek.png
I plan on implementing push pull like this soon.
You did a great job, and just like you , I have been working on plasma speakers for 2-3 years now (ever since I started College). I have been looking at Tobias’ design for quite some time and have found it to be one of the best designs as far as run time goes. But my plasma speakers generaly fail miserably for unknown reasons like my lastest one. One day I test it and it worked beautifully, nice arc with clear sound and no heating of the mosfet or other components. It was like a dream come true from my other designs which blew mosfets like firecrackers. Well a week later after it ran just fine it decided not to work anymore – didn’t touch it- it just didn’t work anymore. It tries to draw over 5amps from the supply and then I thought I wonder if its like what u were saying about the 1st technique in audio modulating the flyback by injecting the audio into the RC timing section and not the dead-time. I really just think my plasma speakers have a grudge on me or something… Other than that every component is fine and functioning normally – leaves me stumped and stupefied. Have you come across this problem were it would just not work anymore for no reason? I can tell you another interesting thing is that my low power side has a separate ground then my high power side and when connecting them both together I get a really week arc and the mosfet gets hot quick, another wierd thing.
Any luck with the new design?
Thanks for sharing the high voltage PSU design!
I haven’t had a chance to try it out yet… work has been keeping me busy 🙁
Do you plan on continuing your testing and design of your plasma speaker in the near future?
I am interested to hear about the new design! Been waiting for months. I like your wordpress template too ; )
Yes, I’ve had some more free time lately, so I think I might be able to get some more plasma speaker work done!
Still wondering how the Plasma Speaker Project is goning?
Thank you for the update. Were you able get a longer ark with the push pull than with the half wave? May be you could put up a quick up date video. I would Really appreciate it. I had a printed circuit board made based on Tobias and your design. It includes the Push pull also. I will let you know how it goes when I get it up and running. Best wishes.
very nice project! i’ve also found the instructables website already and was planning to build one as well. I guess you took a decision with the higher voltage varistor, they seem suitable only for limited pulse loads: http://www.resistorguide.com/varistor/
This is a very nice project, and has my interest piqued, but there are some aspects that are just painful to watch… If I may…
1, why are you using MOSFET driver chips for this? My gut instinct without looking up the FETs you’re using is that the Vgs requirement is excessive. There are several MOSFETs that are better suited for the switching here, and have a much lower Vgs rating. IRFZ44N for example – can be saturated at around 6V. They also have a much better current handling ability, and if for added insurance against popped transistors, get one that is avalanche rated. I drive flybacks experimentally all the time with no snubber whatsoever, no problem. I include them in printed versions of my projects for added insurance, but a suitable transistor can handle what a flyback can dish up. The 494 has a more than adequately qualified totem pole output that can drive these transistors directly.
2, Snubbing reduces the effectiveness of a flyback transformers operation. You WANT rapid collapse of the field in the core to get maximum output efficiency. Snubbing steals some of this energy away from the system, reducing the output, requiring more drive.
3, Try going more with very low duty cycle to establish your arc. This can be difficult to do, as you’ve discovered. Using the caps in parallel with the primary can help, but just as with the snubbers, this method can reduce efficiency. The mechanism is different however, involving dv/dt rather than raw “theft” of the energy. Low duty cycles will help with this, as it will operate more as a class C system than the brute force method that is evident in the scope traces. Less is more in this case.
Last but not least, PWM is your friend here. Tune the chip to the transformer and let resonance do the work! More duty cycle means more current in the arc, which means more heat, which means more air displacement. Let the transformer do the work, not your power supply and MOSFET. You’ll be able to get more SPL out of it, and the transistor will run much cooler.
Email me if you have any questions.
Steve
Great site.
I just built a similar plasma speaker using the same TL494 chip and a MOSFET driver. Works great apart the FET gets very hot even with a big heat sink. Can someone explain why the output of the MOSFET driver is via a 470R and not directly connected to the MOSFET. Would the MOSFET switch quicker if connected directly to the driver chip?
This is a very interesting project, I would like to build one as well. I’m not expert with electronics stuff but I think I can manage it easily, (high voltage, soldering etc not an issue). I have some difficulties to understand the schematic for the version 1.0 of your board. I kindly ask you if you can help me also P.M. with a “foolproof” schematics of the complete board. I would Really appreciate it. Best wishes.