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"9v" ac adapter — Parallax Forums

"9v" ac adapter

ArchiverArchiver Posts: 46,084
edited 2003-04-24 06:59 in General Discussion
hi all,

sorry if you see these kinds of threads over and over.. but i
couldn't find one that really fit with my situation through the
search.

i bought a 9V wall wart and it says it's supposedly outputting 9v at
100mA, but i measured it at 12V with the multimeter. do you think
it's ok to use that with my homework board with bs2 stamp? i don't
want to fry anything.. but i thought there may have been a regulator
onboard the homework board. i didn't know if 12 would be too much
though. thanks for your help in advance.

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-04-24 02:47
    Dear Anthony,
    you have an unregulated power supply and you are reading the "unloaded"
    voltage. make sure the school board has a voltage regulator chip on board
    and you are o.k., if not, look at Mouser electronics. They have some
    regulated wall warts that are great.
    mike m
    Original Message
    From: anntanyango <PennyH1010@a...>
    To: <basicstamps@yahoogroups.com>
    Sent: Wednesday, April 23, 2003 9:36 PM
    Subject: [noparse][[/noparse]basicstamps] "9v" ac adapter


    > hi all,
    >
    > sorry if you see these kinds of threads over and over.. but i
    > couldn't find one that really fit with my situation through the
    > search.
    >
    > i bought a 9V wall wart and it says it's supposedly outputting 9v at
    > 100mA, but i measured it at 12V with the multimeter. do you think
    > it's ok to use that with my homework board with bs2 stamp? i don't
    > want to fry anything.. but i thought there may have been a regulator
    > onboard the homework board. i didn't know if 12 would be too much
    > though. thanks for your help in advance.
    >
    >
    > 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.
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2003-04-24 05:14
    This is a common issue. Cheap wall warts are not regulated. So they will
    be rated at, say 9V@100mA. That means that if you draw 100mA from it,
    the output will drop to about 9V. If you just hook a voltmeter to it, it
    will read a lot more because you aren't drawing anywhere near 100mA (or
    even 1mA) from it. If you are drawing less, the voltage will drop, but
    not to 9V.

    I haven't seen the homework board, but I'm assuming it has a 5V
    regulator and that should be enough although I'm sure Jon or someone
    will chime in with a definite answer. But I wanted to point out that
    with an unregulated supply, the voltage drops with current draw so to
    properly test, you must test under load.

    Al Williams
    AWC
    * NEW: PAK-VIa - Read PS/2 keyboards or mice -- double the buffer, lower
    current consumption.
    http://www.al-williams.com/awce/pak6.htm




    >
    Original Message
    > From: anntanyango [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=DSgTq6Su8eL64NmsyMG0B9YrLydeXp94im61dLHFguw6_7-bLktmQkJEpQtmhqgRQUpqvTK8FairSN_E0A]PennyH1010@a...[/url
    > Sent: Wednesday, April 23, 2003 8:36 PM
    > To: basicstamps@yahoogroups.com
    > Subject: [noparse][[/noparse]basicstamps] "9v" ac adapter
    >
    >
    > hi all,
    >
    > sorry if you see these kinds of threads over and over.. but i
    > couldn't find one that really fit with my situation through the
    > search.
    >
    > i bought a 9V wall wart and it says it's supposedly outputting 9v at
    > 100mA, but i measured it at 12V with the multimeter. do you think
    > it's ok to use that with my homework board with bs2 stamp? i don't
    > want to fry anything.. but i thought there may have been a regulator
    > onboard the homework board. i didn't know if 12 would be too much
    > though. thanks for your help in advance.
    >
    >
    > 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.
    >
    >
    > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2003-04-24 05:46
    The Homework board has an SO-8 surface mount LM2936M-5
    +5V regulator that can easily handle +9-12V input. Just be sure
    not to exceed the 50mA MAX regulated output current limit.

    Regards,

    -Bruce
    tech@r...
    http://www.rentron.com


    Original Message
    From: "anntanyango" <PennyH1010@a...>
    To: <basicstamps@yahoogroups.com>
    Sent: Wednesday, April 23, 2003 7:36 PM
    Subject: [noparse][[/noparse]basicstamps] "9v" ac adapter


    > hi all,
    >
    > sorry if you see these kinds of threads over and over.. but i
    > couldn't find one that really fit with my situation through the
    > search.
    >
    > i bought a 9V wall wart and it says it's supposedly outputting 9v at
    > 100mA, but i measured it at 12V with the multimeter. do you think
    > it's ok to use that with my homework board with bs2 stamp? i don't
    > want to fry anything.. but i thought there may have been a regulator
    > onboard the homework board. i didn't know if 12 would be too much
    > though. thanks for your help in advance.
    >
    >
    > 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.
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2003-04-24 06:44
    I use one of the unregulated 9V supplies from Radio Shack with my stamps, in
    fact the stamp has a regulator on it and it will take a wide range of
    voltages so you won't hurt it if you hook up an unregulated 9V supply to it.
    Al is correct tho, you must test the voltage under the rated load to check
    the supply and make sure it is working correctly.

    Randy Abernathy




    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-04-24 06:59
    Thanks for all the replies! I will be sure to test it out under a
    load and that it should do fine. [noparse]:)[/noparse] Cheers!


    --- In basicstamps@yahoogroups.com, "anntanyango" <PennyH1010@a...>
    wrote:
    > hi all,
    >
    > sorry if you see these kinds of threads over and over.. but i
    > couldn't find one that really fit with my situation through the
    > search.
    >
    > i bought a 9V wall wart and it says it's supposedly outputting 9v
    at
    > 100mA, but i measured it at 12V with the multimeter. do you think
    > it's ok to use that with my homework board with bs2 stamp? i don't
    > want to fry anything.. but i thought there may have been a
    regulator
    > onboard the homework board. i didn't know if 12 would be too much
    > though. thanks for your help in advance.
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