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Electrical Winding 1st toroidal transformer for my DIY Geiger counter

  1. Nov 14, 2011 #1
    First post! :)

    I am building a Geiger counter with this circuit:

    in the blog the author used a regular EI transformer from a power supply, but I tried disassembling them and broke the ferrite core 4 time now, so I am planning on making a toroid transformer from an inductor.

    I have done a lot of research and lot of people are telling me that a toroidal transformer CAN be used instead of an EI one in an inverter circuit such as the one in the Geiger counter.

    So my question is : Should I use insulation between layers like in EI transformers or should I just wrap the layers on each other?

    Also, does it matter if the secondary was wound first rather that the primary/feedback?
  2. jcsd
  3. Nov 15, 2011 #2


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    Save yourself the trouble and buy a CCFL inverter transformer for a couple of bucks that comes with a driven Q1 (and the first 'C' too).

    Winding a transformer for that application is a bit bonkers and if it is the Geiger counter you want then you really just don't want to get into transformer winding!!

    In direct answer, yes, you can wind with anything that forms a magnetic circuit. Each coil is at a different voltage to the next coil (as per the volts/turn value (= rate of change of flux)). So, yes, if those differences are 100's of V then you'd want to insulate them.

    To open up a ferrite transformer, use a heat gun and warm it up, then the bonding glue falls apart. You could try boiling water if you don't have a heat gun.

    But heed my advice; if your interest is in Geiger tubes, forget winding your own transformers unless you are seriously interested in those too!

    If you get a CCFL you will find it is rated to, say, 800 VAC for a 12V input. You'll want around 300 to 400 V for your tube. Try lower input voltages, they usually run fine right down to the switch-on voltage of the oscillating transistor.

    For recitification, you'll need a high voltage, trr<150ns diode on one of the outputs.
  4. Nov 15, 2011 #3
    Thanks so much for your advice
    what about this transformer:
    http://www.abra-electronics.com/products/750%252d00060-12V-Power-Inverter-for-CCFL.html [Broken]

    It seems to be perfect for the job, 660V with 12v ac (i need 400v, so around 9v is good)
    I would have never thought it would be as easy as simply buying one.

    One more question, would this work with the zener diodes on the linked diagram to limit voltage to around 400v and how does it work?
    Last edited by a moderator: May 5, 2017
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