Reduce volts from ESC

Discussion in 'General' started by Z Boat, Aug 30, 2021.

  1. Z Boat

    Z Boat Well-Known Member

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    I have a question. How can I reduce the volts from my ESC to my motors? I have a 4.8V battery nickel metal and a Quicrun 1060 brushed esc with two 3V maxon motors. The radio is an old Attack 4 and I have been running the boat on 3.6V and I would like to run on 3.8V. I can not run the esc on less than 4V so I was wondering if resisters or a potentiometer between esc and motors would work. If anyone has a correct answer please lead me to the light and show a D student how its done. This is for a small boat so room is critical.

    Thank you.
     
  2. darkapollo

    darkapollo Well-Known Member

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    You COULD use a resistor, but there is going to be significant amp draw to the motors which may be an issue.

    From their tech sheet (TYVM for providing the manufacturer)
    https://www.maxongroup.com/maxon/view/product/motor/dcmotor/amax/amax16/110042
    VALUES AT NOMINAL VOLTAGE
    Nominal voltage 3 V
    No load speed 12300 rpm
    No load current 38.1 mA
    Nominal speed 8810 rpm
    Nominal torque (max. continuous torque) 1.3 mNm
    Nominal current (max. continuous current) 0.6 A
    Stall torque 4.51 mNm
    Stall current 1.97 A
    Max. efficiency 75 %

    OHMS law is Voltage = Current * Resistance. But since we know the Voltage and the Current, but want to find the Resistance, we use R = V/C
    R = 3/0.6
    R=5ohm
    You would need a 5ohm resistor to drop the voltage from 4.8 to 3v.
    https://www.calculator.net/ohms-law...t=ampere&r=&runit=ohm&p=&punit=watt&x=44&y=29

    I have a link below to some quality 5ohm resistors with heat sinks, mounting holes, and spade terminals but the forum is being silly and making the link extra small.


    View: https://www.amazon.com/uxcell-Aluminum-Resistor-Wirewound-Converter/dp/B07FDXPP1L/ref=sr_1_2?dchild=1&keywords=5+ohm+10+watt+resistor&qid=1630407663&sr=8-2&tag=rcwaco-20
     
    Last edited: Aug 31, 2021
  3. BigGunJeff

    BigGunJeff Well-Known Member

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  4. Z Boat

    Z Boat Well-Known Member

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    Thank you both.
     
  5. Bob

    Bob Well-Known Member

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    Why do you want to reduce the voltage to your motors when you have an ESC.
    Back in the old days people would use a resistor to drop voltage to slow the ship down.
    Now with ESC you can change speed without one.
     
  6. BigGunJeff

    BigGunJeff Well-Known Member

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    Bob, that's true...

    Z Boat, your ESC is sending full voltage, but in short little bursts. The net effect in a motor is like sending a lower voltage as you are trying to achieve. The advantage here is that you don't waste the electricity as you would by using a resistor.

    You could limit the power to your motor by limiting the top end of your throttle in your radio.
     

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  7. Kotori87

    Kotori87 Well-Known Member

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    Just about the only time you need to lower the actual voltage applied is when you've got an extreme difference between applied voltage and voltage rating. Since insulation ratings and other hardware are based on the intended voltage, a sufficient over-voltage could potentially cause damage to the commutator. I've literally only seen that once though, on a very large industrial 255VDC motor that was regularly started and stopped at 355VDC. The commutator suffered from copper picking until it was bad enough to arc across commutator segments. In most hobby applications, the actual damage is caused by overheating due to over-current. Your 3V maxons are incredible motors, they should easily handle the 4.8V from your batteries. Just use an ESC to reduce your throttle, and it'll do the same thing as a voltage-reducing resistor, without wasting a lot of energy.
     
    darkapollo likes this.
  8. Z Boat

    Z Boat Well-Known Member

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    How? This radio is 34 years old and only has a trim tab (old school) I cannot use one of my newer radios, because this is in my Type IX sub and I want to run the boat on one battery. Even with the tab all the way down it still screams and reverse is even faster. Is there a way to adjust the throw rates in an old radio?
     
  9. BigGunJeff

    BigGunJeff Well-Known Member

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    I could see Three ways of doing it.

    1. Simplest: Make a physical stop that gets attached to the front of the radio to limit stick throw.

    2. Hardest: Solder some resistors to the Positive and Ground pins of the potentiometer in the joystick. This could electronically limit the throw of the stick by changing the voltage divider... We can talk more on that front.

    3. Most Practical: Some ESC's have the ability to set the max output for forward and reverse during a setup process. If this is possible, no equipment modifications would be necessary
     
  10. Bob

    Bob Well-Known Member

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    Maybe better spend $100 and get a better radio.
     
  11. Kotori87

    Kotori87 Well-Known Member

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    This is for a submarine. Modern 2.4ghz radios can't penetrate water. Kinda stuck unless you get your HAM license and buy an expensive Long Range FPV module.