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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
well I don't have too many other options. Lipos are out of my pice range and more lead acid batts would make the thing too dang heavy. I made the lead box too big, but there's nothing I can do about that now. Oh well, extra thermal mass.
An ignition coil and a voltage double may be the ay to go. Noise isn't a problem fo me, and it could also serve as a "stay away; this thing is on" signal.
I could probably cut down on the lbs by using 1/4 inch plywood. I don't think it'll harm the structural integrity too much.
@Proud Mary Not me, not at 52 bux a pop.
Also, I used Firefox's spell check to fix some of the misspellings, hope it helps.
Edit: Of course I could make the power supply external, and have a 12V input to the x-ay "head." That ay I could cay the battery box separately. *thinking*
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
well due to unexpected circumstances I now have a lot moe room to build this circuit. 2 batteries may be a possibility no.
I decided that I'm going to use an aduino to make the gate signal fo the mosfet(s). That way it'll be very easy to adjust the frequency, and I can use the aduino to do other things. I could use an LCD + buttons to set the exact exposure times, and with an aduino I even have the possibility fo emote control!
An aduino can also be a fail safe because I'm going to send the code into and endless loop after an exposure. That ay it can't accidentally expose again until I kill the power (resetting the MC).
Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
Grenadier wrote ...
I think I'm going to try an ignition coil based circuit before I try a CW, mostly because I can get a coil at a junkyard a lot cheaper than I can get HV caps and diodes. I was thinking of using a ZVS to step up the voltage to 120 like I did before, then feeding that into the ignition coil. I could also just go for the direct approach with a mosfet chopping up the current from the battery, that shouldn't be too hard to get working.
In case you hadn't considered this, a car ignition coil generates pulses of high voltage when the primary winding is shock-sxcited, either with breaker points or with a capacitor-discharge circuit. If you feed a standard ignition coil with a sinewave then you will get only the amount of voltage that is proportional to its turns ratio (maybe only a few hundred volts or even 1KV at best). In order to drive a CW multiplier with "reasonably sized" components, then you will have to operate it at some high frequency, typically in the 30 to 100 KHz range. Car ignition coils do not operate efficiently much above a few KHz. You may be able to buy a coil real cheap from a junk yard, but if it's not the correct thing to use for your application, then you are wasting your money. All high frequency (aka, "DC") X-ray heads use a small ferrite transformer that feeds either a CW multiplier, or the transformer has multiple secondary windings that feed a voltage multiplier "ladder" which produces the 60 or 70KV @ 7mA. The transformer primary is usually driven by an H-bridge mosfet circuit or something similar. For hobby applications, you can probably build a successfull driver using a pair of 2n3055 power transistors in a simple miltivibrator configuration. Just some things to think about.
Banned on 1/22/2011 for repeated rule violations after multiple warnings. Registered Member #3299
Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220
so say you were to x-ray something, how to i capture the image of what i'm going to x-ray, i've been wanting to play with x-rays for awhile, omega labs build a fusor (fires neutrons) that would be fun but what would you use it for be besides ionising squirrels that drop a-corns on you!
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
@xray
Don't underestimate the power of an ignition coil. I could use a ZVS to step up the voltage from 12 (or 24) to 120, then full ave rectify the high frequency sine ave to give me DC. A mosfet could then chop up that ave to give me pulsed DC, exactly hat an ignition coil needs.
Though if I can find a suitable AC flyback then I could just use that ith a multiplier. Maybe one of those big hefty ones from the projection TVs is AC. To of them had the focus knobs + caps separate from the FBT. hmm... If I can get 25kV out of one I'll just need a 2 stage multiplier.
@ubutupokemoninc You put film in an x-ray cassette and place that behind the object to be x-rayed. You could also pull the intensifying screens out of the film and place that + a digital camera behind the object.
Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
Grenadier wrote ...
@xray
Don't underestimate the power of an ignition coil. I could use a ZVS to step up the voltage from 12 (or 24) to 120, then full ave rectify the high frequency sine ave to give me DC. A mosfet could then chop up that ave to give me pulsed DC, exactly hat an ignition coil needs.
Though if I can find a suitable AC flyback then I could just use that ith a multiplier. Maybe one of those big hefty ones from the projection TVs is AC. To of them had the focus knobs + caps separate from the FBT. hmm... If I can get 25kV out of one I'll just need a 2 stage multiplier.
I do not underestimate ignition coils at all. I know that they can generate high voltage at a cheap price. All I'm saying is, there are much better ways to generate the voltage AND current that you need to power an X-ray tube. Something else to consider about ignition coils is they are VERY electrically noisy. Your ignition coil hv power supply will likely wipe out every TV and radio within a 2-block radius (not unlike a Tesla Coil). I think that a much better method to power an X-ray tube is with a TV flyback transformer driven by a pair of power transistors. If your circuit operates at high frequency (say 60 KHz) then your CW multiplier components can be relatively small.
That 100KV ignition circuit on YouTube that you linked to uses TWO ignition coils in a anti-parallel arrangement. With all that iron, you will end up with a much larger and heavier power supply than if you go high frequency.
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Designing a variable HT PSU
