Re: Recycled Ferrites III (fwd)

[Steven Roys <sroys@xxxxxxxx>]

---------- Forwarded message ----------
Date: Sat, 20 Dec 2003 08:58:45 -0700
From: robert & june heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Recycled Ferrites III

Just a passing comment. Most people just wind an oscilator primary of 20tct
# 22 wire around a flyback coil  core and 6t ct feed back winding and power
the flyback with a free running mv circuit or a push pull oscilator. Most
flyback coils have pleanty of open space to add wire. While you are removing
the flyback coil don't overlook the deflection coil ferrite. It is 2 to 3
inches in diameter and two piece for easy winding.
   Robert   H
-- 


> From: "High Voltage list" <hvlist@xxxxxxxxxx>
> Date: Fri, 19 Dec 2003 11:07:42 -0700 (MST)
> To: <hvlist@xxxxxxxxxx>
> Subject: Recycled Ferrites III (fwd)
> Resent-From: hvlist@xxxxxxxxxx
> Resent-Date: Fri, 19 Dec 2003 11:07:45 -0700
>
> Original poster: Steven Roys <sroys@xxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Fri, 19 Dec 2003 21:58:08 +1030
> From: Matthew Smith <matt@xxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Recycled Ferrites III
>
> Hi All
>
> Many thanks to those who have provided such helpful advice on my attempts at
> re-using ferrite cored transformers...
>
> Going through all the odds and sods that I have lying around, I have found a
> load of tiny little transformers removed from the flash boards of disposable
> cameras.  These have pretty good turns ratios - may need to watch insulation
> if
> I put more than the usual 1.5V into them.
>
> Looking at an alternative way to drive them (if you put more than 1.5V on the
> entire flash board, you get smoke after a very short time) with a suitably low
> component count.  I have half a rail of LT1171 switching regulators - this is
> the 2.5A/100KHz version of the old LT1170.
>
> Thinking of hooking an LT1170 onto one of these little transformers (goodness
> knows how they will handle 100kHz).  The only topology in the Application Note
> which uses two windings is flyback.  However, I don't think that these
> transformers have a gapped core as a flyback corner should.
>
> Can anyone tell me what would the effect be of running a flyback circuit with
> no
> core gap?  If the energy is stored in the gap, would the lack of gap mean that
> I
> wouldn't get anything out of the secondary?
>
> My proposed test circuit is VERY basic - LT1171, transformer, rectifier,
> capacitor.  I can either hook the feedback pin to ground to enable flyback
> mode
> or just leave it floating.  Maybe the latter would be best, since I would then
> really just have an oscillator driving the switch.  (The application note
> shows
> this as a legitimate way of doing things - this is how higher voltages are
> handled using an external switching element.)
>
> Cheers
>
> M
>
> --
> Matthew Smith
> Kadina Business Consultancy
> South Australia
> http://www.kbc.net.au
>
>