Hello,
We use two SparkFun Brushless 3-Phase Motor-Drivers SparkFun Brushless Motor Driver - 3-Phase (TMC6300) - SparkFun Electronics to control two gimbal SparkFun 12V 3-Phase BLDC motors. The voltage range of each motor-driver is 2-11V. Could you please clarify whether or not the Lipo 11.1V 2200 mAh battery Amazon.com is good to power the motors via the motor-drivers whose voltage range is just 2-11V ? Thank you.
A fully charged 3S battery will exceed 11.1V (3.7V per cell).
Thank you, PaulZC. I am sorry I disagree with you because 3 * 3.7V = 11.1V.
3.7V is the nominal voltage per cell. A fully charged cell will exceed 3.7V. A fully charged 3S battery will exceed 11.1V.
Oh. Yes. You are right. What if to discharge the battery a bit? Thank you.
PaulZC, our project has the microcontroller board RedBoard Artemis ATP SparkFun RedBoard Artemis ATP - SparkFun Electronics , two gimbal 12V 3-Phase BLDC motors, two 3-Phase Brushless motor-drivers. The microcontroller board can be powered via the 7-15V barrel connector. The microcontroller board needs just 3.3V. What if to connect two motors in parallel, but connect the microcontroller board with the two motors in series? Therefore, there will be the voltage drop of 3.3V. As a result, we could power the motors with about 9-10V keeping the battery almost fully charged. Thank you.
That will not work.
Per the datasheet, use a 1S or 2S battery and your troubles are solved.
Also, you’ve asked these questions before and the answers you received then still apply.
Thank you, Yellowdog. Why will that not work? By the way, I did not ask about connecting the battery to the microcontroller board and connecting the latter to the two motors in series.
Hi Boris (@B ),
It is clear that you are just getting started with electronics, microcontrollers and motor circuits. Some of your questions show a complete lack of knowledge. That’s OK. You are among friends here. We all want to help you learn, the same way we did - through advice, experience, trial and error. Sadly, you learn the most when things go wrong. Your motor project may fail initially, but you will learn, gaining experience and knowledge as you go.
My recommendation is to start your journey with the hook up guide. Use that as your starting point. Start with something that has been tried and tested. Replicate it. Then change or add one thing and re-test. Did it work the way you expected? If not, why not. Investigate and learn. That’s the journey…
The barrel connector on the ATP board feeds a linear voltage regulator. It regulates a 7-15V input down to a 3.3V output to power the board. But it is wrong to think that the regulator will subtract (“drop”) 3.3V from the input voltage. It does not work like that. If you were to connect the ATP board in series with the motor drivers, the voltage drop across each will change depending on the current going through both. Also, the regulator on the ATP board will try to limit that current, giving very unpredictable results. The voltage drop across the motor driver would change depending its current draw. Then you have to consider the Ground (0V) voltage for both. If the ATP is “on top” of the motor drivers, its ground voltage will be “on top” of the voltage taken by the motor drivers. If you then try to connect the ATP Ground to the motor driver Ground, which you will need to do to get the PWM to work, you will be short circuiting the power to the motor drivers. Try it if you want to. You will learn a lot. But you may destroy both boards in the process. LiPo batteries can deliver a lot of current…
I hope this helps,
Paul
Thank you, PaulZC. Yes, you are right that a very beginner in electronics. There is no anything to have been tried and tested. Our project is unique. Actually, the motors will work in a completely non-standard way for them. The same is for all the electronic parts.
I understand about the voltage drop. I like your explanation. The motor will work at one speed only. Hence, the current will be the same (approximately the same). Though I have some questions.
You wrote: “Then you have to consider the Ground (0V) voltage for both. If the ATP is “on top” of the motor drivers, its ground voltage will be “on top” of the voltage taken by the motor drivers.” Why do you suppose that the ATP is “on top”?
I would like to highlight the following. The motor power terminals GND and V can be connected to the ground and the positive terminal of the voltage source or vice versa. Simply speaking, the motors do not care of the polarity. However, the microcontroller board really cares of the polarity.
You wrote: “…If you then try to connect the ATP Ground to the motor driver Ground, which you will need to do to get the PWM to work, you will be short circuiting the power to the motor drivers. Try it if you want to.” Why should one connect the ATP Ground to the motor driver Ground, but not to the motor-driver positive terminal? Why can the motor-driver Ground not be directly connected to the battery ground? In this case, the microcontroller board would act as a resistor connected in series, wouldn’t it? Thank you.
Hi Boris (@B ),
No. That is wrong. Where did you get that information? The brushless motor driver cares very much about the polarity. If you reverse the polarity, you will destroy the board.
Try it if you want to. You will learn a lot. But you are very likely to destroy both boards in the process.
Best wishes,
Paul
Hi PaulZC. Can you find anything that prohibits to switch the motor polarity? TS-Russell posted a good picture of the 6 PWM control of the 3-Phase motor commutation: Gimbal 12V motor with encoder AS5048A? - #39 by B . Please take a look at the picture. Do you see something that prohibits to switch the polarity (Ground and V)?
I am sorry. You have not answered my other questions. I would like to repeat them here:
1. You wrote: “Then you have to consider the Ground (0V) voltage for both. If the ATP is “on top” of the motor drivers, its ground voltage will be “on top” of the voltage taken by the motor drivers.” Why do you suppose that the ATP is “on top”?
2. You wrote: “…If you then try to connect the ATP Ground to the motor driver Ground, which you will need to do to get the PWM to work, you will be short circuiting the power to the motor drivers. Try it if you want to.” Why should one connect the ATP Ground to the motor driver Ground, but not to the motor-driver positive terminal? Why can the motor-drivers common Ground (motor-drivers connected in parallel to each other) not be directly connected to the battery ground? In this case, the microcontroller board would act as a resistor connected in series, wouldn’t it? Thank you.
Yes. If you switch the polarity, the MOSFETs inside the driver will be reverse biased. The internal diodes will conduct. With no way to limit the current, you will destroy the motor driver.
If the motor drivers are “on top” of the ATP, it will still not work. What you are proposing, connecting the ATP in series with the motor drivers, will not work.
The ATP and the motor drivers need to share a common ground for the PWM interface to work. It will not work if the ground potential of the ATP or the motor driver is higher than the other.
They can. But the PWM interface will not work unless the ATP shares the same ground voltage.
Thank you for the answers. It is clearer now. I need to reason why the PWM interface will not work if the motor-drivers and the ATP board do not share the same ground.
Arduino circuits need a shared ground to provide a consistent voltage reference point and complete the electrical return path for signals. Without it, voltage levels become meaningless, data signals get corrupted, and electricity cannot flow properly back to its source.
Why Voltage Needs a ReferenceRelative value: Voltage is not an absolute number; it is a difference in electrical potential between two specific spots.The zero mark: Ground acts as the zero-volt baseline.Mismatch risk: If two connected devices use separate power sources without a tied ground, their zero points differ, meaning a 5V signal from an Arduino might look like random noise or the wrong voltage to another board.Completing the Current PathClosed loops: Electricity always needs a complete path to travel out and return home.Data transmission: When an Arduino sends a data bit (like a high 5V pulse) to a sensor, motor driver, or LED strip, that electrical current must complete its loop through the ground wire.Floating signals: If the ground is missing, the signal has no return path, causing erratic behavior, glitching, or complete communication failure.
Thank you, YellowDog. You highlighted the important points. If I understand you correctly, do you mean that the same voltage batteries can be used to separately power the microcontroller board and the motor-drivers, but the batteries’ grounds must be connected together? Thank you.
All the grounds for all your power sources and peripherals need connected together.
An 11.1V LiPo is not suitable directly here. That voltage is only the pack’s nominal voltage.
A fully charged 3S LiPo reaches 12.6V. That exceeds the driver’s 11V maximum rating.
Please do not connect the battery directly. Use a suitable buck converter between them.
Set its output below the driver’s maximum. Around 8V should suit these motors better.
Check the converter’s current rating before choosing one. Two motors may need significant current during operation. Also consider startup and transient currents carefully.
Add appropriate input capacitance near each driver. Keep the battery wiring short and appropriately sized. Use suitable power connectors for these high-current connections.
Check their voltage and current ratings carefully. This approach protects the drivers from overvoltage.
Thank you, billiejeanisnotmylover. I decided to use a Lipo 7.4V 5200 mAh battery.