First, let's examine the USB port on the A6 servo driver:
Its primary function is to connect to the configuration software for parameter setup and commissioning. This USB port receives 5V power from the connected host (PC), which could potentially back-feed into the driver's logic circuitry.
So, when the main power is cut during an E-Stop but the USB cable remains connected, is the 5V from the USB port sufficient to sustain the driver's logic circuitry?
This practice is strictly prohibited.
The specific reasons are as follows:
- Insufficient Power: The USB port (5V/0.5A for USB 2.0) provides very limited power and may be insufficient to reliably power the driver's core logic circuits, encoder feedback circuit, and communication interface simultaneously.
- Violation of Power Sequencing: Servo drivers require strict power-on and power-off sequences. During normal operation, the logic power is typically applied first, followed by the main power. The sequence is reversed during shutdown. Using the USB port to maintain logic power during an E-Stop disrupts this sequence, potentially causing internal state machine errors, register corruption, or communication faults within the driver.
- Prevention of Proper System Reset: After an E-Stop, the system requires a full reset to clear fault statuses and reinitialize the driver. If the logic power remains continuously on, the driver may not complete a full power-off/power-on cycle. This could prevent certain latched faults or states from being cleared, thereby hindering normal system recovery.