Who doesn’t want an X-ray machine? But you need a special tube and super high voltage, right? [Project 326] says no, and produces a USB-powered device that uses a tube you can pick up two for a dollar. You might guess the machine doesn’t generate X-rays with a lot of energy, and you’d be right. But you can make up for it with long exposure times. Check out the video below, with host [Posh Arthur].
The video admits there are limitations, of course. We were somewhat sad that [Project 326] elected not to share the exact parts list and 3D printed files because in the unlikely event someone managed to hurt themselves with it, there could be a hysterical reaction. We agreed, though, that if you are smart enough to handle this, you’ll be smart enough to figure out how to duplicate it — it doesn’t look that hard, and there are plenty of not-so-subtle clues in the video.
The video points out that you can buy used X-ray tube for about $100, but then you need a 70kV power supply. A 1Z11 tube diode has the same basic internal structure, but isn’t optimized for the purpose. But it does emit X-rays as a natural byproduct of its operation, especially with filament voltage.
The high voltage supply needs to supply at least 1mA at about 20 kV. Part of the problem is that with low X-ray emission, you’ll need long exposure times and, thus, a power supply needs to be able to operate for an extended period. We wondered if you could reduce the duty cycle, which might make the exposure time even longer, but should be easier on the power supply.
The device features a wired remote, allowing for a slight distance between the user and the hot tube. USB power is supplied through a USB-C PD device, which provides a higher voltage. In this case, the project utilizes 20V, which is distributed to two DC-DC converters: one to supply the high-voltage anode and another to drive the filament.
To get the image, he’s using self-developing X-ray film made for dental use. It is relatively sensitive and inexpensive (about a dollar a shot). There are also some lead blocks to reduce stray X-ray emission. Many commercial machines are completely enclosed and we think you could do that with this one, if you wanted to.
You need something that will lie flat on the film. How long did it take? A leaf image needed a 50-minute exposure. Some small ICs took 16 hours! Good thing the film is cheap because you have to experiment to get the exposure correct.
This really makes us want to puzzle out the design and build one, too. If you do, please be careful. This project has a lot to not recommend it: high voltage, X-rays, and lead. If you laugh at danger and want a proper machine, you can build one of those, too.
Rustin Cohle wearing a surgeon’s hat and dragging on a ciggy definitely inspires confidence in this endeavor, good choice.
Driving the anode voltage out of USBC for extended periods is worth looking into by itself. All kinds of fun stuff you could do with that… most of them shady, I like it
What’s the difference between “filament voltage” and “high voltage”? It sounds like you’re saying both are involved.
Filament voltage drives the tube’s heater (literally a tungsten filament like a light bulb), for this tube it’s 1.2V at probably 200 mA or so. This emits electrons, as the cathode.
The high voltage (10s of kV, tiny currents in this case) accelerates the electrons, which hit the anode and generate X-rays.
Thank you, that makes it clear. Here’s where I misunderstood: “But it does emit X-rays as a natural byproduct of its operation, especially with filament voltage.”
The tube will produce a bit of output even without heating the filament. Apply a bit of voltage to the filament to heat it, and the x-ray output will increase dramatically.
But, yeah, (sorry Al) it’s a little unclear as written.
This is officially the most terrifying Hackaday headline of the past year.
They’re basically taking advantage of the existing tiny x-ray output of a standard rectifier tube, and then using exposure times up to ten hours long at an extremely close distance. The emitted photons are completely blocked by even the thin copper layer of a PCB.
So while you don’t want to put your finger directly on it, you’re probably as safe a few meters away as if you were near an old tube TV.
Yeah, but if you sat too close to the tele, your eyes would go square – that’s what my mum used to tell me…
I love the video, it is true, generating X-rays is easy enough it is not like it is some really complex process (X-rays were discovered by Wilhelm Conrad Röntgen in 1895). The main thing that has changed over the last 130 years years is our knowledge of how really bad they are for human health. Soft in some ways are even more scary than hard because they are so easily absorbed by soft tissue.
True, low energy “soft” X-rays deposit almost twice as much dose in the first millimeter or two. Scary indeed. The more penetrating higher energy “hard” x-rays get absorbed less in the skin, and go right on through to deposit dose in internal organs.
Sticking your fingertip on the output window of a low-energy x-ray tube is a dumb idea, not because low-energy x-rays deposit more dose, but because you’re sticking your finger a couple of millimeters away from a point radiation source, so the dose per square millimeter is many thousands of times higher than it would be in a usual x-ray imaging setup.
If you can figure a digital sensor for the X-rays, toggling the tube on and off could increase resolution and reduce noise though lock-in sensing. Similar to http://hackaday.com/2024/10/28/lock-in-thermography-on-a-cheap-ir-camera/