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1 Battery, 2 Devices — Parallax Forums

1 Battery, 2 Devices

ArchiverArchiver Posts: 46,084
edited 2002-04-07 14:32 in General Discussion
I want to power two devices with one battery. Not quite sure how to
do it. Here are the specifics...

I have one 9V transistor battery, a Stamp II OEM, and a Serial
Controller. The specs on the Serial Controller are a Supply Voltage
of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.

I know to tie all the grounds together to the battery. Do I send two
positive leads to each device (like spokes on a wheel with the
battery being the "hub"), or do I "daisy chain" the positive lead
from the battery to the Stamp Vin, then from the Stamp Vin to the
Serial Controller?

I understand the difference between wiring things in series and in
parallel, I am just not quite sure which one I should do or if it
even matters.

Any help would be greatly appreciated.

Thanks,

Steve

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2002-04-05 16:44
    Hi Steve,

    Short answer: parallel.

    Long answer:

    Things in parallel get the same voltage and draw their own current.

    Things in series get different voltages but the same current.

    That's why an LED and a resistor work in series. The LED needs a certain
    voltage and will draw a certain amount of current. We compute the
    resistor value to "absorb" the extra voltage at that current (read
    http://www.al-williams.com/wd5gnr/basiccir.htm).

    When you wire things in parallel, they will all have the same voltage
    across them, but each will have its own current independent of the
    others (assuming the supply can provide enough current). Also, as you'd
    expect, the current coming out of the battery will equal the current in
    each branch of the parallel circuit.

    This is how Christmas lights typically work. The 120V is fed to a string
    (series) of lights. The lights each drop, say, 1V and there are 120
    lights/string. And when one burns out, the whole string goes dead.

    Modern lights have a little resistor in the base that doesn't dim the
    light much, but if the light burns out the string doesn't die. Of
    course, if you remove the light or the resistor breaks, that's
    different.

    Al Williams
    AWC
    * 8 channels of PWM
    http://www.al-williams.com/awce/pak5.htm



    >
    Original Message
    > From: sjoblin001 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=YKjcsvtN5pCpuFudk5tYRMyTS3jwp5S49M6kHur3Vwvh49qutKKjs8oOPkKBSUCc2z76h--BdjriKw]sjoblin@m...[/url
    > Sent: Friday, April 05, 2002 9:14 AM
    > To: basicstamps@yahoogroups.com
    > Subject: [noparse][[/noparse]basicstamps] 1 Battery, 2 Devices
    >
    >
    > I want to power two devices with one battery. Not quite sure how to
    > do it. Here are the specifics...
    >
    > I have one 9V transistor battery, a Stamp II OEM, and a Serial
    > Controller. The specs on the Serial Controller are a Supply Voltage
    > of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.
    >
    > I know to tie all the grounds together to the battery. Do I send two
    > positive leads to each device (like spokes on a wheel with the
    > battery being the "hub"), or do I "daisy chain" the positive lead
    > from the battery to the Stamp Vin, then from the Stamp Vin to the
    > Serial Controller?
    >
    > I understand the difference between wiring things in series and in
    > parallel, I am just not quite sure which one I should do or if it
    > even matters.
    >
    > Any help would be greatly appreciated.
    >
    > Thanks,
    >
    > Steve
    >
    >
    > 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 2002-04-05 16:45
    The two options you lay out are electrically identical. You are wiring them in
    parallel, which is the correct way to do it. Serial would be battery positive
    to device 1 positive, then device 1 neg to device 2 pos, device 2 neg to
    ground. That would be a very bad idea. Have fun.

    Clark Hughes

    sjoblin001 wrote:
    >
    > I want to power two devices with one battery. Not quite sure how to
    > do it. Here are the specifics...
    >
    > I have one 9V transistor battery, a Stamp II OEM, and a Serial
    > Controller. The specs on the Serial Controller are a Supply Voltage
    > of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.
    >
    > I know to tie all the grounds together to the battery. Do I send two
    > positive leads to each device (like spokes on a wheel with the
    > battery being the "hub"), or do I "daisy chain" the positive lead
    > from the battery to the Stamp Vin, then from the Stamp Vin to the
    > Serial Controller?
    >
    > I understand the difference between wiring things in series and in
    > parallel, I am just not quite sure which one I should do or if it
    > even matters.
    >
    > Any help would be greatly appreciated.
    >
  • ArchiverArchiver Posts: 46,084
    edited 2002-04-05 16:54
    I would suggest connecting the positive of each device to the positive
    terminal of the battery and do the same for the negative side. This
    would be referred to as parallel. Noise is another factor, and some
    method may be necessary to reduce it if in fact your controller
    produces. You will probably know after you try to make it work. I
    would suggest using a separate battery for power and logic devices.
    Sometimes the grounds maybe tied together and some times not if optical
    coupling is required for the noise issue.

    HTH

    Leroy

    sjoblin001 wrote:
    >
    > I want to power two devices with one battery. Not quite sure how to
    > do it. Here are the specifics...
    >
    > I have one 9V transistor battery, a Stamp II OEM, and a Serial
    > Controller. The specs on the Serial Controller are a Supply Voltage
    > of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.
    >
    > I know to tie all the grounds together to the battery. Do I send two
    > positive leads to each device (like spokes on a wheel with the
    > battery being the "hub"), or do I "daisy chain" the positive lead
    > from the battery to the Stamp Vin, then from the Stamp Vin to the
    > Serial Controller?
    >
    > I understand the difference between wiring things in series and in
    > parallel, I am just not quite sure which one I should do or if it
    > even matters.
    >
    > Any help would be greatly appreciated.
    >
    > Thanks,
    >
    > Steve
    >
    > 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 2002-04-05 17:15
    Oh, I misunderstood the thrust of the question. Yes, when reading my
    email, note the definitions:

    Parallel

    +
    +
    ******| |********
    * +
    + *
    + * +
    + *
    ***********| |***
    +
    + +
    + *
    | | *
    | | *
    | | *
    +-*---+ *
    **********************
    -


    Series


    + +
    + +
    +
    ***********| |*******| |******
    +
    + +
    + +
    + **
    | | *
    | | *
    | | *
    +
    + *
    **************************************
    -


    As Clark point out, your question seems to ask: "Does it matter if I run
    wires from the battery or just go from device to device?" So in the
    parallel drawing if the wire between the + battery and the upper device
    is A and the wire going to the lower device is B, should A and B both go
    to the battery, or is it sufficient to connect A and then connect B to
    the same terminal on the upper device and go to the lower device.

    The short answer is in theory, these are the same and for what you are
    probably doing, either will suffice. However, in practice, I will tell
    you that for high current and/or high noise connections, it is best to
    go straight to the battery. For example, in a car it is common to wire a
    transmitter directly to the battery with thick wire. So in practice,
    sometimes things are different than in theory.

    Al Williams
    AWC
    * Floating point A/D
    http://www.al-williams.com/awce/pak9.htm


    >
    Original Message
    > From: J. Clark Hughes [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=1Ye2fKUm9Hn2KOSYLUO2T2lycyjukR7QVkpM1rPRZTB5hCPtgzncbx0sXKd80UyERUltc0e7jMnd5AhrQOLnFb8U]jchughes@a...[/url
    > Sent: Friday, April 05, 2002 9:46 AM
    > To: basicstamps@yahoogroups.com
    > Subject: Re: [noparse][[/noparse]basicstamps] 1 Battery, 2 Devices
    >
    >
    > The two options you lay out are electrically identical. You
    > are wiring them in parallel, which is the correct way to do
    > it. Serial would be battery positive to device 1 positive,
    > then device 1 neg to device 2 pos, device 2 neg to ground.
    > That would be a very bad idea. Have fun.
    >
    > Clark Hughes
    >
    > sjoblin001 wrote:
    > >
    > > I want to power two devices with one battery. Not quite
    > sure how to
    > > do it. Here are the specifics...
    > >
    > > I have one 9V transistor battery, a Stamp II OEM, and a Serial
    > > Controller. The specs on the Serial Controller are a
    > Supply Voltage
    > > of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.
    > >
    > > I know to tie all the grounds together to the battery. Do
    > I send two
    > > positive leads to each device (like spokes on a wheel with
    > the battery
    > > being the "hub"), or do I "daisy chain" the positive lead from the
    > > battery to the Stamp Vin, then from the Stamp Vin to the Serial
    > > Controller?
    > >
    > > I understand the difference between wiring things in series and in
    > > parallel, I am just not quite sure which one I should do or
    > if it even
    > > matters.
    > >
    > > Any help would be greatly appreciated.
    > >
    >
    > 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 2002-04-05 17:20
    If your wire is fairly thick like 16 to 22ga you can daisy chain with no
    problem, and you could solder in a 100uf- 30v cap across each device (in
    parallel), but you may not really need to, if you do make sure you wire the
    right polarity for the cap. Skip
    Original Message
    From: sjoblin001 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=6e-0qUQ0-F9WDi04R3ULdbDEKhzPWFz-hRrQ52J5cW6xg6JYh7YuVp5IpuWPFyXjnKqS3japevDb2Q]sjoblin@m...[/url
    Sent: Friday, April 05, 2002 10:14 AM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] 1 Battery, 2 Devices


    I want to power two devices with one battery. Not quite sure how to
    do it. Here are the specifics...

    I have one 9V transistor battery, a Stamp II OEM, and a Serial
    Controller. The specs on the Serial Controller are a Supply Voltage
    of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.

    I know to tie all the grounds together to the battery. Do I send two
    positive leads to each device (like spokes on a wheel with the
    battery being the "hub"), or do I "daisy chain" the positive lead
    from the battery to the Stamp Vin, then from the Stamp Vin to the
    Serial Controller?

    I understand the difference between wiring things in series and in
    parallel, I am just not quite sure which one I should do or if it
    even matters.

    Any help would be greatly appreciated.

    Thanks,

    Steve


    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 2002-04-07 14:32
    If you run them like the spokes on the wheel it is the same as daisy
    chaining them but there will be less chance of voltage drops and noise
    between the two.

    At 03:13 PM 4/5/02 +0000, you wrote:
    >I want to power two devices with one battery. Not quite sure how to
    >do it. Here are the specifics...
    >
    >I have one 9V transistor battery, a Stamp II OEM, and a Serial
    >Controller. The specs on the Serial Controller are a Supply Voltage
    >of 5.6 to 20 volts and a Current Consumption of approximately 15 mA.
    >
    >I know to tie all the grounds together to the battery. Do I send two
    >positive leads to each device (like spokes on a wheel with the
    >battery being the "hub"), or do I "daisy chain" the positive lead
    >from the battery to the Stamp Vin, then from the Stamp Vin to the
    >Serial Controller?
    >
    >I understand the difference between wiring things in series and in
    >parallel, I am just not quite sure which one I should do or if it
    >even matters.
    >
    >Any help would be greatly appreciated.
    >
    >Thanks,
    >
    >Steve
    >
    >
    >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/

    Larry G. Nelson Sr.
    mailto:L.Nelson@i...
    http://www.ultranet.com/~nr
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