Square wave amplification from 555 timer oscillator to 20v RMS?

Discussion in 'General Electronics Chat' started by chunkmartinez, Jul 19, 2014.

  1. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    I am wanting to build a wire tracer. I need to generate a 20v rms square wave at 20khz. Is this practical with 3 9v batts? I realize I need a lot more voltage supply then what 3 9v batts will supply, is there a simple DC voltage boosting circuit I can build that is efficient and small? The output dosnt need to supply any real current since it just needs to apply the voltage wave form across a wire and ground and an inductive light tester indicates it is the correct wire(the tester emits a light when you put it near the wire with the tracer signal.

    I want to use an astable 555 timer and amplify the output to 20vrms(which seems harder then I first thought).
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
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    I'm sure someone has a circuit handy, without me drawing one.

    Meanwhile, are you stuck on the 555 model? Other timers work to 40V supply and 50ma outputs.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    You can use a single 9V battery to power the 555 timer and then use a 1:10 step up transformer to increase the output voltage.
     
  4. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Yeah I thought about using a step up transformer...For the amp stage. I also thought about finding a special IC that will take higher rails and find a small transformer. What ICs can work on 40v or more?
     
  5. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Can someone help me find a small transformer for this project to order, or if anyone knows their stuff about smps boost converts that would be interesting. I know they make Ti makes simple switcher buck and boost converters but I cannot find a boost converter
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    You can wind your own pulse transformer on a small ferrite toroid.
     
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  7. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Can you elaborate on this? I have a small toroid or two.
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
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  9. crutschow

    Expert

    Mar 14, 2008
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    The ap note says the LM122 is obsolete.
     
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  10. k7elp60

    Senior Member

    Nov 4, 2008
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    Here is a complete schematic without a transformer. It uses a SG3524 to
    boost the 9V to 28V. I used this for a project some time ago. The values for the 555 are calculated for 20KHZ
     
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  11. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    Mr chips, I didn't realize it yesterday but when you spoke of a pulse transformer, is this the same toroid transformer used in caraudio smps power supplies? Because I have a few small ferrite toroids, and 3 different sizes of small gauge enamel coated wire, and also a lot of tl494 ICs. Maybe I can have the tl494 generate my square wave(20-30khz) then run it through a custom wound step up toroid without the push-pull transistors in between. Well, the transistors would depend on what current is required on the primary and what the IC can handle, right? I may use 3 9v batts to generate the wave as high as I can, then boost through the toroid transformer. I know of a custom toroid design tutorial for higher power apps which I can maybe try.
     
  12. MrChips

    Moderator

    Oct 2, 2009
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    Tomorrow, if I remember, I will breadboard a 555 timer circuit driving a handmade toroid transformer and then let you know the results.
     
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  13. k7elp60

    Senior Member

    Nov 4, 2008
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    You wanted a circuit to generate a square wave at 20v rms at 20khz. The circuit I posted does that. The 555 generates the square wave the SG3524 boosts the single 9V battery to 28V and the 2N3904 transistor gives you your high voltage square wave. What else do you want?
     
    Last edited: Jul 22, 2014
  14. alfacliff

    Well-Known Member

    Dec 13, 2013
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    you should look up the ratings for the toroids, some are only good for vhf or uhf.
     
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  15. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Here is a cute little circuit that may do what you want.:)
    It's a voltage tripler that will generate about 24 volts from the 9 volt battery. It runs at 20Khz so the same 555 switches a little FET for your signal. It won't supply much current, but it may do what you need.
     
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  16. MrChips

    Moderator

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    Cute. Why didn't I think of that?
     
  17. alfacliff

    Well-Known Member

    Dec 13, 2013
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    how about using an audio output transformer backwards? a small one from radio shack. should step up about right.
     
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  18. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    I like your circuit, I was just hoping to not have to order that IC. I figured there was something I already had that I can use.

    I thought about that little audio transformer at RadioShack however I did not think It would have the right ratio. I'd like to check it out now.

    I like all of everyone's input so far..
     
  19. chunkmartinez

    Thread Starter Senior Member

    Jan 6, 2007
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    I tried winding a toroid transformer and tried using another toroid I have but I don't seem to be getting any output on the scope. I am a newb at this though so...

    I am wanting to try the SG3524 circuit posted earlier, or ronv's cute circuit. Ronv, can I substitute the 2n7002 FET for a different fet because I want to order from an American eBay seller for speed but I only see Listings from over-seas...
     
  20. ronv

    AAC Fanatic!

    Nov 12, 2008
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