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Wallwart to BoE — Parallax Forums

Wallwart to BoE

ArchiverArchiver Posts: 46,084
edited 2004-05-03 23:26 in General Discussion
Well this may or may not be a stupid question, I have
just taken delivery of my first stamp (BS2) after some
great advice from this list I opted to get the basic
Education Kit, and so today was the first opportunity
I have had to "play".

At the time of ordering I purchased the appropriate
wallwart from Parallax , so before actually plugging
the power unit into the BoE I checked it with my
multimeter and the reading I got was 16.7V. Is this
right I double checked with a different multimeter and
got the same reading. I thought it was supposed to be
9v? Well I am up and running with a 9v battery for
now. So whilst this message is being posted I can
continue working my way through the WAM manual.

Thanks Nigel




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Comments

  • ArchiverArchiver Posts: 46,084
    edited 2004-05-03 10:57
    Hi Nigel,

    Many have asked the same question, and I discuss it (and a few other things)
    in a little article at:

    http://www.glitchbuster.com/wallwart.htm


    -Randy
    www.glitchbuster.com


    Original Message
    From: "Nigel Emms" <rulingshogun@y...>
    To: <basicstamps@yahoogroups.com>
    Sent: Sunday, May 02, 2004 1:21 PM
    Subject: [noparse][[/noparse]basicstamps] Re: Wallwart to BoE


    > Well this may or may not be a stupid question, I have
    > just taken delivery of my first stamp (BS2) after some
    > great advice from this list I opted to get the basic
    > Education Kit, and so today was the first opportunity
    > I have had to "play".
    >
    > At the time of ordering I purchased the appropriate
    > wallwart from Parallax , so before actually plugging
    > the power unit into the BoE I checked it with my
    > multimeter and the reading I got was 16.7V. Is this
    > right I double checked with a different multimeter and
    > got the same reading. I thought it was supposed to be
    > 9v? Well I am up and running with a 9v battery for
    > now. So whilst this message is being posted I can
    > continue working my way through the WAM manual.
    >
    > Thanks Nigel
    >
    >
    >
    >
    > __________________________________
    > Do you Yahoo!?
    > Win a $20,000 Career Makeover at Yahoo! HotJobs
    > http://hotjobs.sweepstakes.yahoo.com/careermakeover
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject and
    Body of the message will be ignored.
    >
    > Yahoo! Groups Links
    >
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2004-05-03 14:23
    If you follow the link, it has a very complete
    answer. For now, though:
    The open-circuit (nothing connected but a
    high-impedance voltmeter) voltage on a wall-wart
    can be much higher (up to 10 volts or so) than
    the loaded (delivering 100 or 200 mA to a
    circuit) voltage.

    So, your wall-wart is NOT broken, and when you
    actually connect it the voltage should drop some.

    Note the rating (9V at 300 mA) means that when
    it is delivery 300 mA, it SHOULD be AROUND 9volts.
    Wall-warts tend to be very simple (transformer and
    diodes and one capacitor). That's why you have an
    on-board regulator, to take whatever stuff the
    wall-wart hands out, and convert it to nice,
    clean, steady 5Volts.

    --- In basicstamps@yahoogroups.com, "Randy Jones" <randyjones@w...>
    wrote:
    > Hi Nigel,
    >
    > Many have asked the same question, and I discuss it (and a few
    other things)
    > in a little article at:
    >
    > http://www.glitchbuster.com/wallwart.htm
    >
    >
    > -Randy
    > www.glitchbuster.com
    >
    >
    >
    >
    Original Message
    > From: "Nigel Emms" <rulingshogun@y...>
    > To: <basicstamps@yahoogroups.com>
    > Sent: Sunday, May 02, 2004 1:21 PM
    > Subject: [noparse][[/noparse]basicstamps] Re: Wallwart to BoE
    >
    >
    > > Well this may or may not be a stupid question, I have
    > > just taken delivery of my first stamp (BS2) after some
    > > great advice from this list I opted to get the basic
    > > Education Kit, and so today was the first opportunity
    > > I have had to "play".
    > >
    > > At the time of ordering I purchased the appropriate
    > > wallwart from Parallax , so before actually plugging
    > > the power unit into the BoE I checked it with my
    > > multimeter and the reading I got was 16.7V. Is this
    > > right I double checked with a different multimeter and
    > > got the same reading. I thought it was supposed to be
    > > 9v? Well I am up and running with a 9v battery for
    > > now. So whilst this message is being posted I can
    > > continue working my way through the WAM manual.
    > >
    > > Thanks Nigel
    > >
    > >
    > >
    > >
    > > __________________________________
    > > Do you Yahoo!?
    > > Win a $20,000 Career Makeover at Yahoo! HotJobs
    > > http://hotjobs.sweepstakes.yahoo.com/careermakeover
    > >
    > >
    > >
    > > To UNSUBSCRIBE, just send mail to:
    > > basicstamps-unsubscribe@yahoogroups.com
    > > from the same email address that you subscribed. Text in the
    Subject and
    > Body of the message will be ignored.
    > >
    > > Yahoo! Groups Links
    > >
    > >
    > >
    > >
    > >
  • ArchiverArchiver Posts: 46,084
    edited 2004-05-03 20:32
    The 1605 voltage regulator needs to be overdriven. It can be overdriven at
    5.5 volts, or 9V (a 9V battery actually fluctuates fairly widely as to the
    amount of voltage delivered...), or 16.7v, or 12v. The difference is
    dissapated in heat, so if you're going to drive it at 6 VS 16 volts, you
    may want to consider changing the size of your heat sink.

    On Sun, 2 May 2004, Nigel Emms wrote:

    > Well this may or may not be a stupid question, I have
    > just taken delivery of my first stamp (BS2) after some
    > great advice from this list I opted to get the basic
    > Education Kit, and so today was the first opportunity
    > I have had to "play".
    >
    > At the time of ordering I purchased the appropriate
    > wallwart from Parallax , so before actually plugging
    > the power unit into the BoE I checked it with my
    > multimeter and the reading I got was 16.7V. Is this
    > right I double checked with a different multimeter and
    > got the same reading. I thought it was supposed to be
    > 9v? Well I am up and running with a 9v battery for
    > now. So whilst this message is being posted I can
    > continue working my way through the WAM manual.
    >
    > Thanks Nigel
    >
    >
    >
    >
    > __________________________________
    > Do you Yahoo!?
    > Win a $20,000 Career Makeover at Yahoo! HotJobs
    > http://hotjobs.sweepstakes.yahoo.com/careermakeover
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject and Body of the message will be ignored.
    >
    > Yahoo! Groups Links
    >
    >
    >
    >
    >
    >

    Sean T. Lamont, CTO / Chief NetNerd, Abstract Software, Inc. (ServNet)
    Seattle - Bellingham - Vancouver - Portland - Everett - Tacoma - Bremerton
    email: lamont@a... WWW: http://www.serv.net
    "Do not fear mistakes, There Are None" - Miles Davis
  • ArchiverArchiver Posts: 46,084
    edited 2004-05-03 22:19
    > Many have asked the same question, and I discuss it (and a few other things)
    > in a little article at: <http://www.glitchbuster.com/wallwart.htm>.

    Enjoyed the read. Thx.

    BTW: Zialog's eZ80 comes with several "switching" wall warts. NO
    TRANSFORMER! ;-) I believe that this is a sign of things to come. They're
    smaller, lighter, generate less heat and are regulated! Mass production will
    probably make them cheaper than the heavy transformer versions so I can see
    them really taking off.

    --
    Enjoy,
    George Warner,
    Schizophrenic Optimization Scientists
    Apple Developer Technical Support (DTS)
  • ArchiverArchiver Posts: 46,084
    edited 2004-05-03 23:26
    AFAIK, the BOE has an LM2840 regulator and the BS2 an LM2936. However,
    Sean brings up a good point about the heat dissipated by the voltage
    regulator. The BS2's regulator would be more of an issue than the
    BOE's regulator, as the BS2 has no heat sink to replace.

    Looking through Parallax's documentation, I found that they recommend
    keeping Vin under 12V even though they specify 6-15V as valid. It
    seems the consensus has been that your wall wart is most likely working
    just fine, but I would test the voltage at the BS2's Vin pin with
    everything powered up anyhow.

    John Butera

    On May 3, 2004, at 2:32 PM, Sean T. Lamont .lost. wrote:
    >
    > The 1605 voltage regulator needs to be overdriven. It can be
    > overdriven at
    > 5.5 volts, or 9V (a 9V battery actually fluctuates fairly widely as to
    > the
    > amount of voltage delivered...), or 16.7v, or 12v. The difference is
    > dissapated in heat, so if you're going to drive it at 6 VS 16 volts,
    > you
    > may want to consider changing the size of your heat sink.
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