Current draw (throttle control signal) brushless motor controller

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Current draw (throttle control signal) brushless motor controller
November 21, 2020 - 2:54pm

The hall sensor based throttle control for a brushless motor controller is said to output a voltage signal between approx 0.5 to 4.5 volts. 100mA.

If one uses a buck converter to mimic the throttle control's output voltage does it matter what the current is set at on the buck?  The brushless motor controller that uses this signal should only draw the 100 mA regardless shouldn't it?

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It provides 100mA current. Where you want to connect the DC DC buck? Why you need it.

Please elaborate your querry.

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I am trying to automate my winch for hang gliding that I have fabricated.  It uses a brushless scooter hub motor, controlled by the standard type brushless motor controller.

The brushless motor controller is typically controlled by a hand or thumb throttle, a hall sensor based variable voltage output device that uses around 100 mA and outputs a voltage signal between around 0.5V to 4.5V

You can see that I am simulating the thumb throttle control with a buck converter.

The question is do I need to really worry about making a device that limits current to 100 mA or will the system only draw 100 mA even if my power supply is capable of providing more current?  Is it really necessary to make a current limiting circuit at 100 mA?

Here is a link to the application

https://youtu.be/qu6SUUNkWHk

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The buck is to replace the throttle.  If I made a voltage regulator circuit instead of the buck would it have to be exactly at 100mA or would the brushless controller only draw as much current as it needs.  I'm afraid to experiment with higher current from the buck for fear of damaging the controller.

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Actually I'm hoping to use a PIC MCU to adjust the voltage by RF remote control, or at least have it control a transistor based voltage regulator circuit capable of going below 1 volt to prevent false starts of the motor

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It is a good practice to choose a voltage regulator that could provide more current than the current required for the load. The load will pull current what it is rated for or required for operations. Make sure that the voltage output of the regulator is same as the required load voltage.

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Yes thank you for your input, I am aware to make current a bit more than requirement but this is a control signal and not a supply for a load so I was afraid to damage my expensive brushless motor controller by providing too much current.

I don't know if you are familiar but this is a brushless motor controller like you see for an electric bicycle or scooter and I'm simulating the throttle control if it's not clear from my video.

I am trying to control with a MCU and there are microchip MCU that have 100 mA capabable analog pinouts, I was hoping to control without having to go to a buck using one of these, I'll have to experiment.

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I think some people might find these experiments interesting or usefull because you mainly see only stepper motors for their robotics projects, this is a way to use these very robust brushless DC motors (waterproof, strong etc) instead.  You can reverse them with a relay switching setup to change the arrangement of the 3 phase wires to the motor and there are many other capabilities built into the brushless motor controller like regenerative braking etc.

I'm surprised I didn't see examples of such a repurposing of this low cost widely available hub motor in my searching.

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Use a voltage follower circuit across the output. It will not damage the signal and will not draw any current.

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OK, to prevent voltage fluctuations due to transient loads right?  that way I can not go over current but still maintain what is required for the signal.

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A voltage follower use 1x gain amplifier and reproduces the signal exactly (ideal situation) and you can use the signal with no modification or additional circuitry at all. However, if you are planning to drive something havier using the output signal, chhose a proper transistor that would be controlled by the output of the amplifier and the current will same as you want.