Common faults and troubleshooting methods of brushless DC motor controllers

The following is for the controller of PIC16F72 microcontroller

1. The static current of the controller should be within 50MA normally. The current is generally around 1.4A when the motor is unloaded and at the highest speed, and some motors are around 1.8A.

When the control board does not work, you should first check whether the signal light on the board flashes in seconds/times. If the signal light does not flash when the handlebar signal is not added, you should check:

1. Whether the 5V voltage is normal, whether there is a short circuit in the external plug-in, whether there is a tinned short circuit on the board, etc.;

2. Whether the voltage of the second pin of the microcontroller is 5V;

3. Whether the quartz crystal is working;

4. The signal light is damaged

2. Controller current and voltage adjustment

1. Current adjustment: adjust the constantan length (the new program can adjust the resistance (R6) of the LM358's 6th pin to the ground, the value range is 2K to 3.3K, and adjust to the required operating current. (The old 500W program has a better operating effect at 26A to 35A, and the new program has a better effect at 22A to 28A.)

2. Voltage adjustment: The undervoltage sampling circuit is composed of two voltage-dividing resistors from a 48V or 36V power supply to the ground. Usually, the undervoltage point can be adjusted by adjusting the resistance (Ra) connected to the power supply. Because the resistance connected to the ground is usually 1.2K, the undervoltage value and the resistance value can be calculated according to the following formula; Ra=(1.2xv-1.2x3)/3

Example: Using a 48V battery voltage, when the undervoltage V value is 40.5:

Ra=(1.2x40.5-1.2x3)/3-------→Ra=15K

Note: 1.2 is the resistance connected to the ground. The 3 in the test is the AD value of the undervoltage processed by the single-chip microcomputer.

When the undervoltage value needs to be adjusted between 40.5V and 42V, when the full load 1.2K resistor is connected in parallel with 82K, 39K, 36K, 33K, and 30K, the undervoltage corresponds to: 41.04V, 41.65V, 41.75V, 41.86V, and 42V respectively.

3. When the single-chip microcomputer on the control board can work (the signal light should flash without turning the handle), but it cannot work normally, please pay attention to the signal flashing state. The following are common flashing states:

1. The weak signal control part works normally for about seconds/time;

2. Slow flash twice, the circuit is in the braking state;

3. Slow flash 3 times, the constantan to LM358 has incorrect parameters or an open circuit;

4. Slow flash 4 times, there is a fault in the upper bridge to the driver to the output MOS

5. Slow flash 5 times, there is a fault in the lower bridge to the driver to the output MOS;

6. Slow flash 6 times, the 60 degree 120 degree selection and the motor Hall phase sequence are not connected correctly;

7. Slow flash 7 times, the current is too large during operation, the constantan is too long or the reference level of the short circuit detection is too low (the normal value is 20K to 1.2K voltage division):

8. Slow flash 8 times, undervoltage state

9. Fast flash 2 times, waiting for the handle to return to zero (power-on anti-runaway function)

10. Fast flash 3 times, the motor is blocked and stopped;

11. The signal light flashes when the motor is rotating, the Hall line is broken and the phase is missing or the motor is not matched.

The other 3 faults can be inferred and repaired in conjunction with the above status:

1: The motor does not rotate:

a: Insufficient voltage, test whether the voltage of the 3rd pin of the MCU is greater than 3.2V;

b: Whether the brake level connection is normal, detect the 7th pin of the MCU, high level brake as long as the voltage is higher than 2..5V: low level brake voltage is lower than 2.0V;

c: Is the speed control voltage added to the 5th pin of the MCU?

d: The connector is not installed properly, and the output cannot be output due to phase loss.

e: When all the above conditions are met, the output and drive circuits are faulty. When the motor is forced to rotate by external force and there is obvious uneven resistance inside, it is mostly the MOS power tube that is damaged, but some are the front-stage drive transistors that are damaged.

2: The motor rotates; but it is not normal:

a: Whether the 60-degree and 120-degree working mode selection of the controller corresponds:

b: The motor relies on external force, and there is a loud and unstable operation sound when rotating; the output is phase-lost, check the connection line, and the components on the circuit board have leaks, cold soldering, short circuits, wrong soldering, etc.:

c: The Hall signal is wrong, and some motors need to adjust the controller output line or Hall signal line;

d: The motor is not stable when rotating at low speed, mostly because the parameters of the drive circuit components are too different. Test whether the three-phase drive components are wrongly soldered and have poor performance;

3: The motor is easy to stop and has poor load capacity:

a: Whether the controller short-circuit comparison resistors R9 and R10 are 20K or 1.2K:

b: The capacity of capacitor C7 (1000Pf) and dead zone adjustment capacitor C24 (100PF) is too large;

c: The constantan wire is too long (*When the capacity of controller capacitors C7 and C24 is not correct, the working current will be abnormal, which is generally reflected in the large working current and the constantan is adjusted too long);

d: Some components of the drive circuit are leaking and the performance is poor.

4: The current limiting resistor is hot and the static current is too large;

a: There is a short circuit in the detection circuit:

b: Whether there is a wrong soldering of the device in the drive output;

c: Whether the connection in the plug-in corresponds.

5: It is easy to burn the MOS tube or the motor runs normally at low speed. It is easy to burn the MOS tube when the handle rises quickly:

a: Is the HC27 circuit (U3) normal:

b; The voltage of the 21st pin of the single-chip microcomputer is not a logical high level or low level, and its pull-up resistor is open or poorly soldered;

c: The MOS drive signal cannot normally follow the output signal of the single-chip microcomputer, presenting a normal level, which is most likely to cause MOS damage.

6: After the turn signal is added, the signal light goes out, but the motor does not rotate:

a: Is the motor output well connected?

b: The motor Hall is not connected;

c: There is an open circuit or poor soldering or leaking in the drive circuit.