07/04/2019 at 11:45 •
Hi there, I have finally finished my college degree and I can make the paper available for anyone. Due to a limit of 40 pages, I couldn't write it as complete as I wanted but I hope it's helpful.
01/17/2019 at 20:16 •
Hi there everyone, huge thanks to all of you that follow and liked this project. I have had finals now but I have finished and I have some free time to upload new content.
Here you have some pictures:
Winding the transformer with the rudimentary but useful coil winder.
The first level of parts. You can see here an arduino board, a buzzer, the 5.5kV transformer, a fan and the 48VDC PSU.
And above all this, the top level:
- Fast ZVS
- Regular chinese 12V PSU.
- Step-down converter.
- Fuse and extender. The fuse is for the x-ray tube filament. It also contains a voltage divider used by arduino to read the filament voltage and it has other connections for the laser grid.
- Relay module. One of the relays controls the filament. The other enables or disables the Mosfet driver of the ZVS.
- Waterproof box containing the tube and voltage multiplier. Those blue things are HV capacitors placed between the cathode of the tube and mains earth, they stabilize voltage and improve efficiency.
- Vertical laser.
Front with laser grid:
The machine is fully operated by the arduino board. It has no buttons, so a computer is used to send commands to arduino. These are the commands:
- E: check machine status (arduino reads filament voltage and checks the Power_Good signal of the 48V PSU)
- L: check lasers.
- H+percentage: it sets the intensity in percentage for the horizontal laser. Example: H20 sets it by 20%.
- V+percentaje: the same, but for the vertical one.
- P: stop everything. If it's x-raying, it stops; if it was counting down to x-ray, it will stop. The 48V PSU, the filament, the ZVS and the laser grid will be turned off.
- F: read filament voltage and show it on screen.
- C+integer: Sets the countdown. Example: C10 sets a 10 second countdown when you use the x-ray command.
- R+integer: X-ray command. When sent to arduino, the countdown set by the previous command starts. When it reaches 0, arduino turns on the 48V PSU, the ZVS and the filament. The machine will x-ray for as many milliseconds as set by this command. Example: R2000 will x-ray for 2 seconds.
The machine uses a very specific way to stop x-raying. First it stops the 48V PSU and the tube filament at the same time, waits 200 ms and stops the mosfet driver of the ZVS. This is a better way to operate the machine rather than using another relay to cut the current coming from the PSU and going to the ZVS. The ZVS has an inductor that stores energy. If the current is suddenly cut, a high voltage peak will happen on both mosfet drains. To prevent this, arduino simply turns off the PSU, so all energy left in the ZVS leaves it through a fully on mosfet. Then arduino stops the mosfet driver and both mosfets of the ZVS turns off.
That's all for now, see ya in the next update.