Many people misunderstand the operation of MOSFETs in BMS circuits. A common misconception is that the charging FET controls the ground line of the charger, and the discharging FET controls the ground line of the load. But in fact, their behavior is more precise and nuanced than that.     1. Basic Configuration of BMS with N-channel MOSFETs Most lithium-ion BMS boards use two N-channel MOSFETs for controlling charging and discharging. These MOSFETs are connected as follows: Source (S): Connected to B− (battery's negative terminal) Drain (D): Connected to P− (output/input common ground) Gate (G): Controlled by the protection IC When a gate voltage (Vgs) above the threshold is applied, the MOSFET conducts and allows current flow from the Drain to the Source.     2. Difference Between Charge and Discharge MOSFETs The discharge MOSFET is responsible for connecting P− to B− when load discharge is allowed. The charge MOS...

If you've connected your hard drive motor to an ESC and successfully powered it up, congratulations! Now it’s time to take control—literally. In this 4th post, we’ll explore how to adjust the motor’s speed using PWM (Pulse Width Modulation), both with and without an Arduino. Why settle for a motor that only spins at one speed when you can build a smarter, adjustable rotary tool? PWM is not just a switch. It’s a fine-grained method for controlling speed and torque by sending carefully timed digital signals. If you want to cut, polish, or sand with precision, PWM control is your secret weapon.     1. What is PWM and Why Does It Matter? PWM (Pulse Width Modulation) is a technique where a digital signal rapidly switches ON and OFF within a fixed time cycle. By changing the “duty cycle” (how long the signal stays ON in each cycle), we control how much power is delivered to the motor. For example: 100% duty = full speed 50% duty = half speed 0% d...