Connect with us

Cockcroft-walton voltage multiplier

Discussion in 'General Electronics Discussion' started by kong, Sep 19, 2012.

  1. kong

    kong

    122
    2
    Sep 26, 2010
    Hey forum,

    I'm planning on building a cockcroft walton voltage multiplier with 1n4007 diodes and 10nf 1000v capacitors.

    I was wondering what I could use as a source voltage to drive the thing

    I was thinking like those inverters from laser printers and such that take a low voltage dc and jack it up to run the fluorescent tubes?

    something along those lines. Is that plausible?

    And if so, is there a way to find out how much voltage they output?

    Thanks in advance.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    A cheap option is a flash unit from a disposable camera (if you can find one) as they have pretty limited energy as long as you remove the main cap -- which you need to do to get AC.

    They will generally produce about 200VAC (or more).

    You do need to consider frequency. 1N4007's are not high speed diodes. At high frequencies they look more like capacitors than diodes.
     
  3. kong

    kong

    122
    2
    Sep 26, 2010
    That sounds doable, would I just solder wires to where the main cap was?

    Also, do you have a suitable substitute to the 1n4007? I just thought those would work because of their high voltage rating.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    That's about it. Just make sure you get the polarity right. Use the polarity of the capacitor as a guide.

    I did this a couple of years ago and was able to use it to pull arcs about an inch long.

    It's also fun to see what it does to things like the xenon flash tube and fluorescent tubes.
     
  5. kong

    kong

    122
    2
    Sep 26, 2010
    Would the high voltage diodes out of a microwave be suitable?

    What exactly is a high speed diode?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    A high speed diode is one that has low junction capacitance (generally speaking).

    I have no idea what the frequency of a flash inverter is. The diodes in the multiplier I used were designed for 50Hz but seemed to work OK.

    You would be better of choosing a diode that is capable of lower currents. You're only going to have milliamps flowing through this circuit, not amps. A 1N4007 is an overkill.
     
  7. kong

    kong

    122
    2
    Sep 26, 2010
    Ok, I figure first I'll measure the current output of whatever I'm driving the multiplier with, (disposable camera charging circuit), and then find a suitable diode. I was hoping for high voltage diodes (4kv) or so around 100mA or less probably....

    also do you think I could use a small audio transformer and 555 setup with a 3055 switching the transformer instead of a camera flash unit? This way I could control the frequency. This is the transformer I had in mind http://www.radioshack.com/product/index.jsp?productId=2103254
     
  8. kong

    kong

    122
    2
    Sep 26, 2010
    It responds to freq. from 300Hz to 10khz
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    You should be able to get 3000V easily. But I'd be surprised if you can get anything even close to 1mA, probably an order or more of magnitude lower.

    The flash charger circuit is already designed to transfer significant power to the high voltage side. It's a good start because you don't have to experiment and worry about insulation breakdown in the transformer (for example).
     
  10. kong

    kong

    122
    2
    Sep 26, 2010
    Ah, I see. Ok, I'll give that a try then.

    Your thoughts on a salvage from a laser printer or photocopier? (CCFL inverter)

    Would that be similar to a flash unit do you think? I'm just trying to come up with the cheapest option. I have access to a dumpster that usually has a laser printer or something in it.

    Would that supply current up to like 2mA?

    Just questions, if you don't know the answers it's no big deal I can research it.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    A low impedance high voltage source can be dangerous. Be careful.

    I don't have any specific information regarding those alternative sources.

    Note that the supply you use to power the multiplier will need to supply more current than you can draw from the higher voltage.

    Ignoring losses (and there are many), simply speaking, the output voltage times output current cannot exceed the input voltage times the input current.
     
  12. kong

    kong

    122
    2
    Sep 26, 2010
    I was considering, in the case of a camera unit, one AA or two to make 3v

    If I end up with a different 'driver' I will probably use a single 9 volt.

    Yes, I have and will take precautions with the inherent dangers of the high voltage, but especially the current.

    Because that's the stuff that kills you ;)

    If I go the route of the audio transformer, I should be safe as the 555 osc I'm using to drive it runs on a 9 volt and as you said, the current is likely to be less that 1mA.

    I did a test on the output terminals of the transformer and it gives you a good zap, but would be better after it is multiplied.

    If I go the camera unit route, it is much more powerful, and that requires precautions because that delivers a nasty shock

    And finally the most dangerous from the three is the CCFL inverter, which supplies voltages around 1000v and currents up to 6mA. Which, under certain conditions can kill, although with dry palms on one hand, I'm not sure, but I don't intend to find out.

    Thanks for the help, when I get a chance I'll pry open a disposable. (being sure to discharge the cap before anything else)
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-