Introduction: STEREO FLYBACK DRIVER
This is my design of a stereo flyback driver. (ZVS) You can drive 2 flyback transformers to create a 2 channel sound ( Stereo ). You can use square wave music as the sound sourse.
It's a fun little project that you can use to create awesome videos. Also, you will learn how to drive Flyback transformers; a technique that was used in old TV sets but if becoming less and less every day.
You can use any flyback transformer that you would like. Play around with old transformers that you harvest from old tv's or just buy new onces at Aliexpress or elsewhere.
Be careful
This is a High Voltage Project. Use it at your own risk. Working with High voltage and / or electricity in general is for trained people only.
Disclaimer:
I, Mark Donners, The Electronics Engineer, may or may not endorse various Do-It-Yourself (DIY) projects and all DIY projects are purely “at your own risk”. As with any DIY project, unfamiliarity with the tools and process can be dangerous. Posts should be construed as theoretical advice only.
If you are at all uncomfortable or inexperienced working on these projects (especially but not limited to electronics and mechanical), please reconsider doing the job yourself. It is very possible on any DIY project to damage belongings or void your property insurance, create a hazardous condition, or harm or even kill yourself or others.
I will not be held responsible for any injury due to the misuse or misunderstanding of any DIY project.
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Disclaimer short version:
This is a DIY project, use any provided information and/or materials at your own risk! I am not responsible for what you do with it!
Supplies
PCB:
Buy it at my Tindie store you have two options
- PCB only no components.
- PCB with most components installed
Buy it here: https://www.tindie.com/products/markdonners/pcb-stereo-flyback-driver/
Or buy it at PCBWAY.com. They offer great PCB’s and assembly for a good price!
(Link to PCBway project side will be added later)
Assuming you bought the pre-assembled pcb, you'll still need to add the following:
2x IRFP260N mosfet
2x 1N4148 diode
2x NE555N timer ( DIL-8)
2x LM311N comparator ( DIL-8)
If you bought the pcb only, you'll have to look at the manual.pdf for the complete list of components.
Flyback transformer
There many kinds of flyback transformers you can use. I used this one:
You will need 2
Power supply
This unit draws a lot of current. The rush in current each time a spark starts is approx. 8 amps per unit. So, you'll need a firm power supply that gives out 24V DC and can handle the high current. I used two Leas-Acid batteries from an old UPS that I had around and I connected them in series to get the 24V. To give you an idea, the batteries have a capacity of 7Ah and it took me less then 30minutes to drain them..
Attachments
Step 1: Schematic Explained. What Are We Dealing With?
The schematic can be divided into 3 sections. The bottom part shows the power connector ( P2) This is to connect the power. Pin 1 = ground ( negative) and pin 2 = 24V ( Positive). 24V is only needed to feed the flyback transformers. the test of the electronics only needs 12V that is why a Zener Diode D2 with serial resistor R15 are used. If all is well, LED LED2 will light up as soon as the unit has power.
The upper half of the schematic is the same is the middle parts. One half is used for the left channel and the other half is used for the right channel.
Both input connectors( P1 and P3) are connected with the jackinput J1 using jumper JP1. If you are planning to use the jack plug, you'll need to short all three pins of jp1.
The audio signal has to be a square wave audio file, that is very important as normal audio jumps all over the place, giving a result that is far from what we consider to be audio. I converted a midi file using Studio FL. In a nutshell, I attached a VST square wave generator to the midi channels I want to convert and saved is as an MP3 file.
The audio signal goes to the LM311 Comperator that is set at a threshold. Every time the threshold is breached, the Output of the LM311 enabled the NE555 Timer. When the NE555 timer is enabled, it runs at 22,5Khz ( adjustable by R4, R27) and it drives a Mosfet. The Mosfet drives your Flyback transformer that is connected to P20 / P4
The output of the NE555 is also connected to a led to see whenever the channel is receiving audio.
Step 2: PCB Assembly
Assuming that you bought the PCB with the components, you'll need to add:
D1 and D3 : 1N4148
U1 and U3: LM311N
U2 and U6 : NE555p
Finally, you need to place Q1 and Q3 on a large heatsink. I used two heatsinks and placed it below the PCB using isolated. spacers. I soldered them at the bottom of the PCb but I made sure that the connection of the pins is still correct. The heatsinks should touch each other. If you use 1 heatsinks for both Mosfets, you'll need to isolate both from the heatsink using isolated thermal pads.
Step 3: Prepairing the Flyback Transformers
You'll have to make the primary winding for each transformer by winding a thick wire 8 times around the ferite core. I used a wire with 1.0mm2 core. I fixed the wire in place using small ty-raps.
I soldered a thick wire the the ground connection of flyback transformer and I connected it to a big metal plate. This is were the high voltage arcs will jump to.
Step 4: Show Time
Before you power up this unit, remember to work safely! High voltage is not pleasant when touched and moreover, it can kill you!Do not use this if you don't know what you are doing!
But he, if you're able to work with this safely, here is a video how it looks like and moreover, how it sounds:
