# LGB Tenders Motor Control



## LGB333$$$$ (Oct 11, 2017)

Some LGB tenders have Dip Switches inside the cover that can be used to reduce the DC analog voltage going to the motor. The Dip Switches help to sync the tender's motor speed with a coupled locomotive's motor speed. Some of you electrical engineer types can help with this question. What can I install into a DC analog-powered tender to provide the same motor voltage control feature as the LGB factory Dip Switches do.......diodes? What about using instead a POT?


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## Greg Elmassian (Jan 3, 2008)

in general resistors are a bad idea

You are trying to induce a voltage drop to the motor.

Diodes are a fixed voltage, irrespective of the current. about 0.7 volts for silicon, maybe 0.3 for a FET, add them in series, and works well. I have shown a "voltage dropper" circuit many times, and you can add or subtract single diodes with switches for user adjustments.

Read that section, a schematic and picture are provided:





Misc. electronics


Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers




elmassian.com





Resistors are NOT a constant voltage drop, the voltage drop varies as the current varies. Result is what appears to be "erratic" operation. This comes from Ohms law: V = I times R. A simple law to calculate voltage, current, resistance.

Greg


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## piercedandan (9 mo ago)

Reason for the dip switches is there is different electronics in new Stainz locos built with removable bottom on motor block. Older ones with split cases always had track power directly to the motors. Older power tenders also had direct wires to motor blocks.


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## LGB333$$$$ (Oct 11, 2017)

Greg Elmassian said:


> in general resistors are a bad idea
> 
> You are trying to induce a voltage drop to the motor.
> 
> ...


I review the helpful diode information on your Website...........thanks!


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## Greg Elmassian (Jan 3, 2008)

You could use switches to "short" across a diode to effectively reduce the number of dropping diodes. Of course the switch would need to handle full motor current.

Greg


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