PWM controller for Rokuhan Shorty

ZandT Jan 2, 2021

  1. ZandT

    ZandT TrainBoard Member

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    I’d like to build a small diorama with a custom PWM controller like the one in this YouTube video:


    I currently have the battery-operated (2 AA batteries) Rokuhan RC004. I don’t need power for lights, just for the tracks. I don’t know much about current, voltage, resistors, amps... Although, I can solder and have soldered LED lights with a battery holder before.

    Can I use any one of these PWM controller and hook up to a battery holder? The first controller says 6V, can I use a 4 AA battery holder and the second one says 3V, can I use 2 AA battery holder?

    6V 12V 24V 3A 80W DC Motor Speed Controller (PWM) Adjustable Reversible Motor Driver Switch https://www.amazon.com/dp/B07BLWXXQC/ref=cm_sw_r_cp_api_glc_fabc_hua8FbM9H43DF

    Low Voltage Dc 1.8v 3v 5v 6v 12v 2a Motor Speed Controller https://www.amazon.com/dp/B07P2BLG2L/ref=cm_sw_r_cp_api_glc_fabc_Cva8FbAPME6HY?_encoding=UTF8&psc=1

    I can’t tell if these controllers are safe to run the Rokuhan Shorty trains.

    Thank you!
     
  2. rray

    rray Staff Member

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    Hi ZandT, Welcome to Trainboard. I looked up those controllers and they should work fine. You can use a 6V wall wart, or 4 AA batteries with the top one and 3V with the lower one. I would go with the 6V one so you can use other locos with it.

    I have ran my shorty with a 470 ohm resistor in series with the motor on 10v DC and 12v DCC without problems.
     
    ZandT likes this.
  3. Kurt Moose

    Kurt Moose TrainBoard Member

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    Wow, that's nice with some amazing details!(y)

    Well done!
     
  4. ZandT

    ZandT TrainBoard Member

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    Thanks @rray Will I need to add a resistor to the 6V controller unit? What is the difference between using 3V, 6V, or 9V as the power source, will it run faster/longer/better control...etc? In the video, they use a 9V battery. Thank you!

    @Kurt Moose Yes, it does have amazing detail, I would be lucky if mine turns out half as nice as that :LOL: But it definitely gives me excellent inspiration.
     
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  5. SJ Z-man

    SJ Z-man TrainBoard Member

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    You can use either but the LEDMOMO has the Reversing switch (it may not me where you want it tho). You can also use any light dimmer that comes in the plastic boxes with connectors on the sides.

    The only issue with ANY of these or other aftermarkets is Current. These do not protect for a short until 3 Amps or so. The Rokuhan will trip at MUCH lower current, protecting your precious cargo :) This can be solved using a low current wall-art and the 5V category used EVERYwhere have a good choice of currents, say o.5 Amps (500 mA)

    Note: I have used many of these in various projects (mostly lighting) and many do not turn on from 0. They need to reach a certain voltage to turn on (so nothing moves until you twist the know far enough). Same if you are running and turn the controller power off, then back on (with the knob in the same place as it was).

    Also, near everyone of these PWM controllers CANNOT output all the way to 0.0 volts. Usually a few % of full 100% PWM. So this an sometimes cause creep. This is principle that Rokuhan uses for the 'Stay On' lighting. The low duty cycle isn't enough to move the motors but the light boards keep getting 'pinged' a few hundred times a second to keep the LED Capacitor storage full. Many are 50-500 Hz for frequency.
     
  6. ZandT

    ZandT TrainBoard Member

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    @SJ Z-man Thanks for all the info. Is there a way to safely use the battery option? I want the unit to be portable and not have to worry about finding an outlet to plug in the AC adapter.
     
  7. rray

    rray Staff Member

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    You can safely use either of them with the 6V battery option. You do not need a resistor unless you find the PMW is causing creep like Jeff pointed out. Yes there are lots of PWM controllers that the duty cycle is enough to allow very slow crawling of your loco at the slowest speed.

    You can simply put the resistor inline with the controller output to your track without modifying your loco., or just turn the battery pack switch off when you stop the loco if your loco creeps.

    I would just use the 4 battery 6v supply, and see if you have any creeping before deciding to add a resistor.

    10-15 years ago you would have to fork over $30-50 bucks for a purpose built PWM controller like this, but in these Arduino Everywhere days, all the experimenter hobby electronics you could ever dream for are available ready to run in the $5 or less range. And the sizes are tiny!
     
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  8. CNE1899

    CNE1899 TrainBoard Member

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    TB,
    I like the idea of the tiny layout.
    What's the theme for your diorama gonna be? Inquiring minds want to know.

    Scott
     
  9. ZandT

    ZandT TrainBoard Member

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    @CNE1899 Half of the layout will be in the Japanese city and half mountainous/nature. I am still in the planning stage, see how to fit all the details in this tiny diorama!
     
  10. CNE1899

    CNE1899 TrainBoard Member

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