AVR-Chat

Russell Shaw wrote:

> Kathy Quinlan wrote:
> 
>>Russell Shaw wrote:
>>
>>
>>>Kathy Quinlan wrote:
>>>
>>>
>>>>Hi all,
>>>>
>>>>I need to find Bmax for a core set I plan to use, I am using a ETD34 with 3C90 
>>>>ferites, but I can not find the Bmax :(
>>>>
>>>>Anyone have any idea ??
>>>>
>>>>I have spent all night looking lol, (found lots of good data on other parts, 
>>>>but no this one)
>>>
>>>0.33T.
>>>
>>
>>Thanks Mate,
>>
>>I have a few more Q's:
>>
>>When winding a Transformer, if I wind the turns to one end, and that is 
>>enough, is it wrong to bring the end of the wire back down the transformer 
>>parallel to the core center leg ? or should I wind half to the end, then wind 
>>the other half back to the beginning ?
> 
> 
> Assuming there's more than ~5 turns, it won't matter. It's more important
> to insulate it from any high voltage secondaries.
> 
> 
>>The transformer whistles badly, it is no where near the switching Freq 
>>(~52Khz) is this due to the way I wound it ?
> 
> 
> No. The feedback loop needs slope compensation if it's the cycle-by-cycle
> regulation type. If it's a slow averaging integrator type loop, it's a
> matter of rethinking the integrator gain and damping coefficients.
> If you have a high voltage secondary, the switching frequency may
> be too high.
> 
> 
>>Where can I buy materials to gap the cores, it says no metallic, so I guess 
>>anything I can get in sizes of say 1,2,5,10,20 mils would be fine :)
> 
> 
> If you need lots, a tapes wholesaler might be a good place because they wind
> the tape onto metre-long roles before cutting it. Get some offcuts off them
> that haven't had the sticky stuff put on (assuming they don't import it already
> coated). The tape place i last went to had yellow mylar transformer tape.
> 
> Other places would be plastics wholesalers, but it'll be hard to get small
> quantities unless they have offcuts.
> 
> Another option (which i've done) is poke around the stationary section at
> K-mart or Officeworks with a micrometre;)
> 
> What i do is just keep all kinds of plastic sheet such as cellophane packaging
> wrappers, christmas wrappers, that really thin cellophane off pre-coated PCB blanks,
> anti-static bags, etc.
> 
> 
>>At least it does start, and sort of works, the output is a bit low, but I used 
>>just 1n4007 diodes instead of shotkey for the rectifier and the ones in the 
>>circuits around the primary (they were specked at controlled avalanche ones 
>>(1n5062 IIRC) But I can not find any in stock and no where is really open till 
>>Tuesday lol.

I have uploaded the design, PSU.pdf.

It should work ok, it is from the appnotes lol



-- 
Regards,

Kat.
---------------------------------------------------------------
  K.A.Q. Electronics     Website: www.kaqelectronics.dyndns.org
  IM: Yahoo: PinkyDwaggy MSN: katinka@kaqelectronics.dyndns.org
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