Powering a flyback without any special circuitry?

Discussion in 'The Projects Forum' started by shadowdude77, Oct 18, 2009.

  1. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Hi everyone, so I just opened up an old monitor that was previously destined for the dump in hopes of being able to use it as a HV power supply to power something like a Jacob's Ladder (as a start, I'll probably expand to other things eventually).

    I just got the case off the monitor and discharged the anode via the standard grounded screwdriver trick. I didn't hear any noise, but I pulled off the suction cup and touched it to various metal objects, so yeah, it's now safe to touch the anode. But I haven't done anything else.

    Anyway, the point of me making this thread is because I was wondering if it's possible to drive the flyback without building my own circuit. I'd rather not have to order the transistor and find a 24V DC transformer that puts out enough current.

    So I had an idea. If the flyback was able to function in the monitor and the monitor was connected to mains power, clearly the monitor must contain circuitry to power the flyback off mains, right? Is there any way for me to preserve this circuitry? I don't care if I have to take out huge sections of the monitor to do this, I'd be fine with having a huge, clunky power supply. But I would think that it should be possible. Can anyone point me in the right direction?

    PS- If it doesn't work out can I just lead the HV and ground wires from the flyback out of the monitor's case, close it up, and run HV straight out of my monitor? I'm okay with this too if it works well enough.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Be careful here, you are dealing with lethel voltages and current.

    Another good use for it's HV supply, google lifters.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    The most dangerous part is when the CRT is charged up; that's a good bit of stored energy.

    As far as usable parts from the monitor to drive the HV flyback; it would depend on the monitor brand. Some brands were notorious for failures in the HV section; my memory fails me which ones offhand.

    Still, working with HV is somewhat hazardous even at fairly low current.

    We like for n00b's to stay with under around 50VDC and 30VAC until they have a good bit of experience under their belts. The possibility of being injured or killed outright is all too real, even if you DO have experience.
     
  4. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Yes, I am aware of the dangers, but I discharged the anode clip so there is no risk of that shock hazard anymore. The only risk anymore is the input (mains) voltage which is present when working with pretty much anything.

    And that is a very cool experiment. But I will still need to find a way to get that HV out of the transformer to perform it. :p

    So the question still stands, does anyone know how I can preserve the circuitry in the monitor so I can run the flyback directly off of mains? If I'm being far too vague I apologize, but I am pretty new at this and you may need to ask me for specifics before I can provide them. Thank you very much in advance.
     
  5. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Well, I have worked with some circuitry at low voltages. I've made the world's slowest HHO generator using one of those 18V <1A doorbell transformers from Home Depot because I refused to waste batteries. ;)

    And then I tried to make a power supply out of a computer PSU but both of the supplies I've tried opening up used aluminium wires instead of copper and as far as I know, it's near-impossible to solder aluminium wire.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Well, right now about all that we know is that you have "an old monitor with a CRT".

    Manufacturer and model would be a good start.

    Sometimes, you can find schematics on the WWW.

    More often, you have to buy them from someplace, like Howard W Sams Publications "Fotofacts".
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Interesting; I didn't know they were using aluminum wiring in PSU's nowadays.

    No, you can't solder aluminum wiring. However, you can coat the aluminum wire with anti-oxidant, and use wire nuts to join them to copper wiring.
     
  8. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    I don't even know if you can classify them as "nowadays"; they were both salvaged from old Pentium IIs! :confused:

    At least I'm assuming it's aluminium wiring. The fact that I couldn't solder to them after about an hour of trying means they can't be just tinned copper or something.

    I can't find any distinguishing mark on the monitor that would look like a manufacturer, except maybe Jean? The model number on the back of the case says JD156N

    EDIT: About using wire nuts on a PC PSU, with the amount those things cost and the number of them I'd have to use, I think I'd be better off just buying a pre-made high current PSU online. :(
    Guess I just got unlucky and got two particularly cheaply-made PSUs...
     
    Last edited: Oct 18, 2009
  9. SgtWookie

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    Jul 17, 2007
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    Odd.

    It could be aluminum, or the wiring could have corrosion or contamination on it.

    A Google search for JD156N didn't turn up much of anything helpful. I gave up after five pages.

    Like I said, it might've been contamination or corrosion.
    It may be possible that they were aluminum wires. But if the wires were soldered into the PCB of the supply, then they probably were tinned copper.
     
  10. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    No, the wire was clean and VERY shiny and the entire length of it from the circuit board all the way up to the molex/motherboard connectors was that color. You think the entire wire was tinned copper? Do they do that? Also, it might be worth noting that in both cases, the wires were stranded. I don't know if that makes a difference but I'm just saying. I don't really think they were tinned copper, especially considering how nice and shiny and perfect they looked, and the fact that it was near-impossible to solder to it with rosin-core and flux-core solder.

    And thanks a lot for your work on my monitor issue. I figured, it seemed like a relatively unknown brand. I've never heard of it.

    I guess I'll have to make the circuit by myself. There were two circuits I was looking at:

    http://www.electro-tech-online.com/...transformer-driver-circuit-flyback-driver.gif

    http://wiki.4hv.org/images/thumb/7/7c/Mazilli2.jpg/800px-Mazilli2.jpg

    The second one looks really complex and I doubt I could pull it off. The first one does look quite simple though, except I have no idea what to do with the whole feedback, primary, and secondary part. Does this mean that I should take the primary off the flyback and wind my own? How would I do this? And what is the feedback coil? How do I "attach" the feedback, primary, and secondary coils together? I know they're not supposed to be electrically attached to each other, and they're supposed to be wound around a ferrite core, right? But how should I separate them from one another, what order do I wind them in on the core, etc.? Sorry, I'm just really confused by this.

    Also, I was planning on using that PC PSU to power this circuit as well because it's perfect (12V DC at several amps), but that proves to be a problem. I'll have to keep hunting for that too.
     
  11. CDRIVE

    Senior Member

    Jul 1, 2008
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    Have you looked into a neon sign transformer for a source of a Jacobs Ladder power supply? I think they'll throw quite an arc.
     
  12. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Well yeah, that's the most popular source of HV for a Jacob's Ladder, but I don't know how to go about getting one. Any sources you'd be able to recommend for me? Rules and regulations on stuff where I live is, unfortunately, really really tight and I'd probably be hard-pressed to find a way to just get high voltage sources handed to me for free, and I'd rather not pay for the transformer.

    Another (very dangerous) alternative I was considering was a MOT cause it'd probably be easier to find a broken microwave (the MOT is usually the last thing to go; the magnetron tends to die first) than it would be to find a NST. I'm rather terrified of them, though, considering they put out 2000VAC and are not current limited in the slightest. That's pretty much instant death as soon as you touch the outputs. If I were to get my hands on one of them it'd be the perfect candidate for a voltage multiplier circuit with some el cheapo 4000V capacitors though, not only to get higher voltages but also to make it less deadly. They also plug straight into the mains which is a huge plus to me.

    Edit: Hmm, another high voltage experiment that looks interesting to me is Kirlian photography. Just throwing that out there in case my experimentation goals change what I should be aiming for in terms of a supply.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    No, don't fool around with a MOT. Good way to wind up dead.
     
  14. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Yeah, I figured as much.

    So, that last question still stands. Can anyone give me a general guideline on what I'm supposed to do with the coils in that simpler circuit: http://www.electro-tech-online.com/...transformer-driver-circuit-flyback-driver.gif

    Why do I need to make my own primary when the flyback has one already? And what's the feedback coil, and how am I supposed to wire this all up?

    Sorry if I'm asking a lot, this aspect of circuitry is just completely new to me and I have no idea where to start. I've tried various search terms on Google and I haven't gotten much.
     
  15. beenthere

    Retired Moderator

    Apr 20, 2004
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  16. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Yes, and I have seen this page, and the site that it links to about how to use flybacks. In fact I am planning on using the circuit on the site that it links to. The only thing is I've never dealt with the whole primary/feedback/secondary part of that circuit. I can definitely build the circuit but I don't know how to build the ferrite-core transformer (I'm assuming that's what it is) portion of the circuit. How are the feedback, primary, and secondary supposed to be connected? Can I just place them in any position on the same ferrite rod as long as they're not electrically connected?
     
  17. CDRIVE

    Senior Member

    Jul 1, 2008
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    Why not just discard the CRT and then use the board as is or did you say the HV was kaput?
     
  18. shadowdude77

    Thread Starter New Member

    Sep 30, 2009
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    Yeah, that's what I had initially said in the thread, but since nobody told me that it would work, I thought I need to know exactly where everything is (SgtWookie told me I should try to find a schematic) or I'd have to wire my own driver. It doesn't help that every site out there just tells you to make your own driver. I thought it would just be common sense to use the circuitry already provided if it's possible, so I assumed that it isn't possible to do it since I haven't seen any documentation on it.

    So it is possible to just chuck the CRT and use it? Or if I wanted to be even lazier, is it possible to just pull the ground and anode wires from the flyback off and simply use it like this while leaving EVERYTHING else in the monitor totally untouched?
     
  19. CDRIVE

    Senior Member

    Jul 1, 2008
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    Unless I'm missing something I would have to say yes to both of your questions. If you pull the second anode off of the CRT and bring a grounded screw driver near it it should throw an arc. When it's on of course. ;)
     
  20. CDRIVE

    Senior Member

    Jul 1, 2008
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    Safety Note!

    The electrodes of a Jacobs Ladder should always be unclosed in a glass or Plexiglas envelope. Hot air must be allowed to exit from the top. Also, the electrode spacing at the bottom of the ladder should be closer than the gap at the top of the ladder.
     
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