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Resistance for Battery Power

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  • Bim Bousman
    Hello again regarding battery power for Z equipment... Today I experimented with a 9 volt battery and some resistors using a 8895 and a 88051, both with 5 pole
    Message 1 of 4 , Nov 16, 2001
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      Hello again regarding battery power for Z equipment...

      Today I experimented with a 9 volt battery and some resistors using a 8895 and a
      88051, both with 5 pole motors. I have some of the little 9 volt battery
      holder-with-reversing switch 'controllers' that Marklin puts into their 81520
      Start Set.

      With 50 ohms resistance in series, neither lok would run.
      With no resistor in series, neither flew off of the track, but I am not sure
      why.
      With 10 ohms in series, both ran much too fast, but not nearly as fast as with
      no resistor at all.
      With 20 ohms in series, both ran too fast, but possibly at prototype
      down-a-steep-hill-with-the-throttle-wide-open speed.
      With 30 ohms in series, both ran at what looked to me like might be considered
      acceptable speed.

      The 10 ohm resistors that I used are all 1/4 watt, I believe, and none of them
      got hot to the touch during testing.

      Conclusion: If you want to run your 8895 or 88051 (and probably many other
      Marklin Z models as well) off of a 9 volt battery, a reversing switch and a 0-40
      or 0-50 ohm variable resistor should do the job.

      There are lots of other battery holders available at Radio Shack and such...
      if you were going to run a layout for a long time from a battery, a battery
      charger, holder for 4 "D" Batteries and a smaller resistor would probably make
      more sense than the 9 volt jobber.

      Bim Bousman
      Honolulu Hawaii
      ************************
    • FR.model@t-online.de
      Bim Bousman schrieb: ... Hi, I can agree the attempts Bim Bousman has made but it is not a good solution for a model railroad power pack. There are some simple
      Message 2 of 4 , Nov 17, 2001
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        Bim Bousman schrieb:

        ...............................
        > Conclusion: If you want to run your 8895 or 88051 (and probably many other
        > Marklin Z models as well) off of a 9 volt battery, a reversing switch and a
        > 0-40
        > or 0-50 ohm variable resistor should do the job.

        Hi,

        I can agree the attempts Bim Bousman has made but it is not a good solution for
        a model railroad power pack.

        There are some simple physical equations that underline this. I want to try to
        explain this with my rough english:

        The current flow (amperage) of a motor is determined by its momentum ( load )
        The speed of motor is determined by the voltage at its brushes.

        If the speed of the motor is reduced by voltage drop of a series resistor
        the amount of speed reduction is related to one special load point only. If the
        load changes ( ramp, curve, train length ) everything else will change too
        momentum -> amperage -> resistors voltage drop -> voltage at the motor -> speed

        A power pack with this features can not sadisfy the modeler.

        Have a look at my simple diagram

        ^
        speed I
        (rpm) I \------------ ideal motor without resistor
        I \
        I \
        I \
        I \
        I \
        I \ with series resistor
        I \
        I_________\______

        momentum >
        (Nm)

        You can see well that the speed goes strong down with the load. The higher the
        value of the resistor ( Ohms ) the steeper the curve in the diagramm. The ideal
        motor without series resistor ( constant voltage ) doesn´t change it´s speed if
        the load is changed. Coreless motors have nearly this feature.

        The only good way to use a battery for a power pack is the combination with a
        voltage regulator circuit ( like mentioned some days ago ). It sounds difficult
        but it isn´t. The circuit is needed only plus a variable resistor ( voltage
        divider ) for it´s adjustment pin - nothing else. Both devices cost about $1
        each. The output voltage of this circuit is not determined by the amperage (
        load ). It is determined by the position of the variable resistor only. Best
        would be to put a capacitor ( about 0.1 microF or more ) parallel to the
        circuits output to prevent demages caused by voltage peaks of the motor.

        The circuit has two additional advantages too. It has a minimum voltage drop to
        reduce the output voltage at about 7.5 ... 8 volts maximum. And ! it has an
        internal overload protector.

        I hope this helps for further attempts,

        Harald Freudenreich
      • td25scorpio@ntlworld.com
        ... many other ... switch and a ... solution for ... want to try to ... momentum ( load ) ... resistor ... only. If the ... change too ... motor - speed ...
        Message 3 of 4 , Nov 17, 2001
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          --- In z_scale@y..., FR.model@t... wrote:
          > Bim Bousman schrieb:
          >
          > ...............................
          > > Conclusion: If you want to run your 8895 or 88051 (and probably
          many other
          > > Marklin Z models as well) off of a 9 volt battery, a reversing
          switch and a
          > > 0-40
          > > or 0-50 ohm variable resistor should do the job.
          >
          > Hi,
          >
          > I can agree the attempts Bim Bousman has made but it is not a good
          solution for
          > a model railroad power pack.
          >
          > There are some simple physical equations that underline this. I
          want to try to
          > explain this with my rough english:
          >
          > The current flow (amperage) of a motor is determined by its
          momentum ( load )
          > The speed of motor is determined by the voltage at its brushes.
          >
          > If the speed of the motor is reduced by voltage drop of a series
          resistor
          > the amount of speed reduction is related to one special load point
          only. If the
          > load changes ( ramp, curve, train length ) everything else will
          change too
          > momentum -> amperage -> resistors voltage drop -> voltage at the
          motor -> speed
          >
          > A power pack with this features can not sadisfy the modeler.
          >
          > Have a look at my simple diagram
          >
          > ^
          > speed I
          > (rpm) I \------------ ideal motor without resistor
          > I \
          > I \
          > I \
          > I \
          > I \
          > I \ with series resistor
          > I \
          > I_________\______
          >
          > momentum >
          > (Nm)
          >
          > You can see well that the speed goes strong down with the load. The
          higher the
          > value of the resistor ( Ohms ) the steeper the curve in the
          diagramm. The ideal
          > motor without series resistor ( constant voltage ) doesn´t change
          it´s speed if
          > the load is changed. Coreless motors have nearly this feature.
          >
          > The only good way to use a battery for a power pack is the
          combination with a
          > voltage regulator circuit ( like mentioned some days ago ). It
          sounds difficult
          > but it isn´t. The circuit is needed only plus a variable resistor (
          voltage
          > divider ) for it´s adjustment pin - nothing else. Both devices cost
          about $1
          > each. The output voltage of this circuit is not determined by the
          amperage (
          > load ). It is determined by the position of the variable resistor
          only. Best
          > would be to put a capacitor ( about 0.1 microF or more ) parallel
          to the
          > circuits output to prevent demages caused by voltage peaks of the
          motor.
          >
          > The circuit has two additional advantages too. It has a minimum
          voltage drop to
          > reduce the output voltage at about 7.5 ... 8 volts maximum. And !
          it has an
          > internal overload protector.
          >
          > I hope this helps for further attempts,
          >
          > Harald Freudenreich

          i use Potentiometers , which is similar to what Harald mentions
          with the variable resistor , i pay the equivalent of $2 for these.
          they are the same as what Noch and Marklin use in there briefcase
          layouts with battery power operation.
          regards
          simon
        • Bim Bousman
          Hello Mike... I have no idea what the problem might be..... mechanical bind?? Loss of power?? Dirty tracks or wheels?? I believe that ( unless the
          Message 4 of 4 , Dec 4, 2001
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            Hello Mike...

            I have no idea what the problem might be..... mechanical bind?? Loss of
            power?? Dirty tracks or wheels??

            I believe that ( unless the resistor is burned out and no longer conducting )
            that using a higher wattge will not do any good.

            First I would check for mechanical binds (to avoid 'frying' the motor), then go
            after other possible causes.

            Like maybe measuring the voltage on the track...

            I am forwarding this to the Z List to see what kinds of answers might show up.

            Lots of luck!!

            Bim B
            ******************************
            ----- Original Message -----
            From: <mike.nosal@...>
            To: "Bim Bousman" <bim@...>
            Sent: Tuesday, December 04, 2001 8:53 AM
            Subject: Re: Resistance for Battery Power


            > --- In z_scale@y..., "Bim Bousman" <bim@s...> wrote:
            > > Hello again regarding battery power for Z equipment...
            > >
            > > Today I experimented with a 9 volt battery and some resistors using
            > a 8895 and a
            > > 88051, both with 5 pole motors. I have some of the little 9 volt
            > battery
            > > holder-with-reversing switch 'controllers' that Marklin puts into
            > their 81520
            > > Start Set.
            >
            > Hi there. I'm new to Z. I just got the 81520 starter set. I saw your
            > post and wanted to slow my train down too.
            >
            > >...
            > > With 30 ohms in series, both ran at what looked to me like might be
            > considered
            > > acceptable speed.
            > >
            > > The 10 ohm resistors that I used are all 1/4 watt, I believe, and
            > none of them
            > > got hot to the touch during testing.
            >
            > I'm using a 27 ohm 1/4 watt resistor in series with a fresh 9V
            > battery.
            >
            > The train goes once around the oval (at a sedate speed) and then
            > jerks to a stop. The resistor doesn't feel hot, but could it be
            > overloading? Should I try a 1/2 watt resistor? Anything else?
            >
            > Thanks in advance,
            > Mike Nosal
            > mike.nosal@...
            >
            >
            >
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