embedded ethernet

ArchiverArchiver Posts: 46,084
edited 2000-03-16 - 17:01:00 in Microcontrollers
>how can i test the
> transformer on them to see what the ratio it is?
>

I think the formula is:

Np/Ns = SQRT(Zp/Zs)

Where:
Np=number of turns on primary
Ns=number of turns on secondary
Zp=impedance of primary
Zs=impedance of secondary

I think that you can just substitute Z with measured inductance of the
windings and make either Np or Ns as unity(1) and Ns or Np will give you the
turns ratio you are looking for.

David

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-03-11 - 19:02:00
    Hi Stampers,

    I have been working on a embedded ethernet project for use with a BS2. Gary
    @ www.embeddedethernet.com did a very nice project but is no longer making
    any kits so I'v been trying to put together a board of my own. I could'nt
    get my hands on the Crystal CS8900A-CQ so I'm using the Crystal CS8900A-CQ3
    (3.3v ver.) I'v got all the parts I need except the ethernet isolation
    transformer. Does anyone know where i can get one? It needs to be a 1:2.5 on
    TX and 1:1 on RX I can't locate one anywhere, heck I can't even find one to
    use with the 5v chip (1:1.414 TX 1:1 RX) I would be grateful for any help,
    also I have a bunch of lan cards kicking around how can i test the
    transformer on them to see what the ratio it is?


    Mike
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-12 - 20:49:00
    David,

    Thanks for that formula it will be a big help to me :-)
    Original Message
    From: David Covick <dac@w...>
    To: PIC STAMP LIST <basicstamps@egroups.com>
    Sent: Saturday, March 11, 2000 8:06 AM
    Subject: [noparse][[/noparse]basicstamps] Re: embedded ethernet


    > >how can i test the
    > > transformer on them to see what the ratio it is?
    > >
    >
    > I think the formula is:
    >
    > Np/Ns = SQRT(Zp/Zs)
    >
    > Where:
    > Np=number of turns on primary
    > Ns=number of turns on secondary
    > Zp=impedance of primary
    > Zs=impedance of secondary
    >
    > I think that you can just substitute Z with measured inductance of the
    > windings and make either Np or Ns as unity(1) and Ns or Np will give you
    the
    > turns ratio you are looking for.
    >
    > David
    >
    >
    >
    >
    > -- 20 megs of disk space in your group's Document Vault
    > -- http://www.egroups.com/docvault/basicstamps/?m=1
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-13 - 03:12:00
    Have you tried TRW they used to be the people for telephone tmrs etc.
    You could probably use the under a $ ones from Mouser used in the audio field.
    Big selection too..

    From: "Mike" <Mike@m...>
    To: <basicstamps@egroups.com>
    Date sent: Sat, 11 Mar 2000 11:02:11 -0800
    Send reply to: basicstamps@egroups.com
    Subject: [noparse][[/noparse]basicstamps] embedded ethernet

    >
    > Hi Stampers,
    >
    > I have been working on a embedded ethernet project for use with a BS2. Gary
    > @ www.embeddedethernet.com did a very nice project but is no longer making
    > any kits so I'v been trying to put together a board of my own. I could'nt
    > get my hands on the Crystal CS8900A-CQ so I'm using the Crystal CS8900A-CQ3
    > (3.3v ver.) I'v got all the parts I need except the ethernet isolation
    > transformer. Does anyone know where i can get one? It needs to be a 1:2.5 on
    > TX and 1:1 on RX I can't locate one anywhere, heck I can't even find one to
    > use with the 5v chip (1:1.414 TX 1:1 RX) I would be grateful for any help,
    > also I have a bunch of lan cards kicking around how can i test the
    > transformer on them to see what the ratio it is?
    >
    >
    > Mike
    >
    >
    >
    > -- Easily schedule meetings and events using the group calendar!
    > -- http://www.egroups.com/cal?listname=basicstamps&m=1
    >
    >


    ron... the motor man...
    Ronald Doctors
    http://www.members.home.net/rdoctors
  • ArchiverArchiver Posts: 46,084
    edited 2000-03-16 - 17:01:00
    Try www.pulseeng.com. They have a selection guide to help choose the correct
    transformer for your chip. They are also good with samples.

    Chris Waters

    >
    Original Message
    > From: Mike [noparse][[/noparse]mailto:Mike@m...]
    > Sent: Saturday, March 11, 2000 11:02 AM
    > To: basicstamps@egroups.com
    > Subject: [noparse][[/noparse]basicstamps] embedded ethernet
    >
    >
    >
    > Hi Stampers,
    >
    > I have been working on a embedded ethernet project for use with a
    > BS2. Gary
    > @ www.embeddedethernet.com did a very nice project but is no longer making
    > any kits so I'v been trying to put together a board of my own. I could'nt
    > get my hands on the Crystal CS8900A-CQ so I'm using the Crystal
    > CS8900A-CQ3
    > (3.3v ver.) I'v got all the parts I need except the ethernet isolation
    > transformer. Does anyone know where i can get one? It needs to be
    > a 1:2.5 on
    > TX and 1:1 on RX I can't locate one anywhere, heck I can't even
    > find one to
    > use with the 5v chip (1:1.414 TX 1:1 RX) I would be grateful for any help,
    > also I have a bunch of lan cards kicking around how can i test the
    > transformer on them to see what the ratio it is?
    >
    >
    > Mike
    >
    >
    >
    > -- Easily schedule meetings and events using the group calendar!
    > -- http://www.egroups.com/cal?listname=basicstamps&m=1
    >
    >
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