Cathode Ray Tube Leads The Way On This Bot

[Daqq’s] latest creation is this little robot with a CRT mounted on the front. Obviously ‘why?’ is the wrong question here, but we know this is right up his alley considering his propensity for the less common like this plasma ball Nixie tube. The solidly-built bot uses two stepper motor controlled wheels and an omni-wheel on the front to create a trike. An ATmega128 controls the system but the real story here is the CRT. It requires a hefty voltage regulator for the -600V to +200V the Tungsram DG7-123 tube needs. Trouble along the way ranged from dealing with stray magnetic fields from the power supply, to mounting the fragile tube itself. Take a look at his detailed writeup linked above and join us after the break for the demo videos.



32 thoughts on “Cathode Ray Tube Leads The Way On This Bot

  1. @mrgoogfan,

    1) There’s no way that much leaded glass would do any appreciable attenuation to xrays. And it’s not xrays coming through the tube it’s electrons. It’s the stopping of electrons that make xrays (by bremstralung literally stopping radiation) lead would stop the electrons nicely :P

    2) You have a point =[

  2. @Drew

    I’m pretty sure it’s not Bremsstrahlung. The phosphors have specific emission spectra (RGB, yeah?). Incoming electrons energize or eject electrons in the phosphors, and radiation is emitted when the vacant spots are filled. Bremsstrahlung is the radiation caused by the actual stopping of the electrons. It’s kindof like blackbody radiation—it has a continuous specturm.

  3. Also, i know a little less about the mechanics here in a tv, but cooling isn’t really an issue, is it? There’s not a whole lot of current flowing, just high voltages. High (mostly static) voltages don’t require cooling.

  4. @kristian,

    You missed the start of the convo. I was asking how hard it’d be to up the potential and use it as an xray gen. I know what bremsstrahlung is, it’s my job.

  5. I really like it …
    In the world of LCD. TFT, OLED, etc. its a kind of post-modern steampunk robot.

    I miss a little smiley face on the CRT with this sinusodial waves form the mouth….

    However, I wonder how long the batteries last with this power hungry CRT

  6. @dan

    not at the normal energies in the tube, but at 40kv they sure will. The lead glass will attenuate it still.

    I know what bremsstrahlung is. In fact I am building an x-ray machine now. It should be done in a month.

  7. It doesn’t matter what the electrons strike. You will get x-rays at sufficient acceleration voltages. Of course, radiation efficiency will depend on the material.


    Sounds awesome… any hints how you are constructing it? I always wanted to build my own by salvaging an electron gun from an old B&W tube and using it in a Coolidge tube arrangement.

  8. @Totti: Well, there are extra batteries for feeding the fillament. They last for about 3-4 hours per charge. As for the main batteries, they last depending on the usage – the robot eats from 80mA (just sitting there, displaying stuff) to 700mA (warp speed ahead!).

    Thanks for the post modern steampunk comment! Great idea!

    @everyone: Xrays are not a problem, given that the acceleration voltages are max 800V (worst case scenario, the farthest cathode to the deflection plates @ max.).

    @polymath: The wavy effect is nice, and I’d keep it there. THe problem is, when the frequency from the transformers is not a multiple (or somewhere around a multiple) of the display redraw frequency, it becomes illegible – it begins jumping about. I can do a video during the weekend. The wavy effect is very nice at other times.

  9. take a look inside a standard crt monitor/tv, there are large straps of copper near the outer edge of the crt tube… (i think they are powered) im fairly sure that would take care of the “wavy” image.

  10. It sure is cute (but isn’t it a bit like leading with your chin? :)).

    CRT’s don’t have anodes, but at high enough voltages (40+kV) they can certainly produce soft X-rays. If I wanted X-rays a CRT wouldn’t be my first choice. Going back a few decades C.L.Stong ‘The Amateur Scientist’ in Scientific American featured a home-made X-ray machine which used a *very* old valve with a heavily gettered dome top (and *lots* of volts). Was republished in a book of collected articles.

    Cathode Punk!

    Brill! Love it.

    @Mu Metal
    Mu metal is used for shielding CRTs in o’scopes.

    True, but I’ve used a short length of ordinary steel pipe around the gun area on CRO builds and it’s effective enough (and a hellofalot cheaper).

  11. heres a simple way to get rid of the ripple: put a copper wire cage around the transformers, or tube itself. this is how you protect electronics from nautral emps, such as solar storms.

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