Parts in Mumbai (India) - Page 64 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th July 2013, 10:19 AM   #631
diyAudio Member
 
Join Date: Nov 2009
Location: Pune
If you need copper for shielding then why not use Aluminium? I use My wife's kitchen, aluminium foil wrap for the purpose.In case if this helps you too..
__________________
There is always a first time....
  Reply With Quote
Old 29th July 2013, 10:28 AM   #632
Roushon is offline Roushon  India
diyAudio Member
 
Join Date: Sep 2004
Location: Mumbai (Bombay)
Quote:
Originally Posted by Aucosticraft View Post
If you need copper for shielding then why not use Aluminium? I use My wife's kitchen, aluminium foil wrap for the purpose.In case if this helps you too..
That is a good idea to shield transformers, but I need it to
shield the digital section IC in my cd player also. There I need to solder it to the ground. Also not sure if aluminum
will be a very good shield. Have no knowledge about
the physics behind all these very much.

Roushon.
__________________
S. Roushon
  Reply With Quote
Old 30th July 2013, 04:55 AM   #633
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
You can use iron to shield the IC but for transformer, copper is preferred. Al will work but you will have to put more layers.

I will post photos of a shielded transformer from a Sony for your reference. Shielding is not the same as covering the transformer.

Gajanan Phadte
  Reply With Quote
Old 30th July 2013, 06:12 AM   #634
Roushon is offline Roushon  India
diyAudio Member
 
Join Date: Sep 2004
Location: Mumbai (Bombay)
My naive understanding says that better the metal better
the shield.

I look forward to the pictures of the shield. Thanks!

Roushon.
__________________
S. Roushon
  Reply With Quote
Old 31st July 2013, 04:47 AM   #635
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
Default shield on transformer

Here is the transformer from a Sony MHC RV50. The mu metal on which the s. no. is printed has three turns of the sheet. The pin side was on the left side of the stereo, mounted on a pcb for voltage selection, the fuses and a small aux power supply. The right side of the stereo had the main pcb, towards the shield on the transformer.

Gajanan Phadte
Attached Images
File Type: jpg 1.JPG (33.2 KB, 52 views)
File Type: jpg 2.JPG (42.5 KB, 52 views)
  Reply With Quote
Old 31st July 2013, 06:51 AM   #636
Roushon is offline Roushon  India
diyAudio Member
 
Join Date: Sep 2004
Location: Mumbai (Bombay)
Thanks a lot for the instruction. If I understand correctly
there are three turns of iron sheets and a copper wrap on the winding and the iron and copper cover are perpendicular to each other.

Regards
Roushon.
__________________
S. Roushon
  Reply With Quote
Old 31st July 2013, 09:49 AM   #637
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
There is no relation(perpendicular) between copper and MU metal. It just happens and is not a requirement.

But see that you wind the copper from outside the core.

Gajanan Phadte

There are three turns of mu(not iron) metal, so better u put more of iron turns.

Last edited by gmphadte; 31st July 2013 at 09:51 AM. Reason: added content
  Reply With Quote
Old 31st July 2013, 11:46 AM   #638
Roushon is offline Roushon  India
diyAudio Member
 
Join Date: Sep 2004
Location: Mumbai (Bombay)
Is there any local version of the name `mu metal' so that
shops will understand....

Roushon.
__________________
S. Roushon
  Reply With Quote
Old 31st July 2013, 12:42 PM   #639
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
I believe mu-metal has no alternative name here and possibly very hard to get here. I don't believe it is made in the country as we import a lot of transformer lamination's. They are bought in bulk and punched to size over here. Thin copper foil is available from many shops selling metal sheets. Try smaller shops as they will sell small quantities.

Why do you need mu-metal in any case ? You should be able to get hum free audio designs using toroid transformers. In pre-amps you could put the transformer in a separate box like some high end companies do.

I felt a brief note to understand the different types of shielding in transformers would be useful to all and searched for a link on the Net.

Here is one:

( from : why shield are used in HF transformer? | LinkedIn )

Ray R. There is a lot of confusion around this topic here.

There are two types of shields - one which is wrapped around the transformer after it is completely wound, and which is shorted to itself and to the core. This is sometimes known as a "belly-band" shield and is used to stop the core and outer windings from acting as radiating surfaces.

The other type of shield is used between windings to minimize interwinding capacitance. This is referred to as a faraday shield. It must not be a complete turn.

Thin foils are used for both types of shields for maximum effectiveness.

Proper grounding of both types of shields is crucial. They must be tied via a low impedance path to a quiet node of the circuit, otherwise their effectiveness will be compromised. The faraday shield is usually tied to a quiet node on the primary, and the intent is to return the high-frequency noise generated by primary switching, through as short a path as possible to either the + rail or the return path, which may well be another pin on the transformer.

For large transformers, shields are sometimes grounded at more than one point.

For ultra-isolation transformers, as many as three shields can be used to dramatically drop capacitance.

The shields are very effective at reducing EMI, especially common-mode. They are very common in medical supplies where input filter common-mode capacitance is limited by agency rules. Even very low-cost flyback for medical applications usually have faraday shields in them.

More information on high-frequency transformer design can be found at Ridley Engineering | - Solutions for Switching Power Supplies in the design center.

I hope this helps answer your question.


Ray R. Negative aspects of shields (ie why we don't always use them)

1) extra process adds cost

2) maintaining isolation standards between primary and secondary is complicated by the presence of the faraday shield. foil must be completely insulated with tape, or appropriate margins applied.

3) termination of faraday shield is awkward - either the foil must be brought out of winding for large transformers, or wires soldered to the foil to terminate it.

4) leakage inductance is increased with the faraday shield. with a 1 or 2 mil foil, this increase can be manageable, and worthwhile for the big drop in capacitance and noise.

5) PCB transformers can benefit from shields, but i don't see this applied as often as it should be.

6) Just to iterate - be careful with where you ground them, as this can eliminate the effectiveness of the shields if not done properly.
__________________
AM
  Reply With Quote
Old 1st August 2013, 04:54 AM   #640
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
Some reading about transformers

Technical Library | Signal Transformer

Gajanan Phadte
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
[INDIA] Any DIYer made a Gainclone in India. willing to help? smarcher Chip Amps 63 2nd January 2014 11:07 AM
Parts availability in India ashok Parts 1 8th June 2011 05:49 PM
I am from Mumbai, India. rakeshln Introductions 2 10th June 2004 03:39 PM
DIY Audio parts sourcing for Live Sound Reinforcement in India peterpan73 Parts 0 19th February 2004 11:28 AM


New To Site? Need Help?

All times are GMT. The time now is 06:57 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2