Electronics > Projects, Designs, and Technical Stuff
Turning a motor on that uses RS485 modbus communication
rf+tech:
Okay, good start, but this is odd that A B inputs seem to be unused. Let’s just say that “fire and forget” without feedback is not expected bus behavior.
Two-wire RS485 would use one Tx and one Rx on the controller and all nodes. Recheck the RJ-45 connections to the chip. Either A and Y, or B and Z, would be required for two-wire communication.
The next steps should be to trace out the copper track paths from transceiver A B inputs looking for any additional components that might be in series to the RJ-45. Establishing the bus as either two-wire, or four-wire, is first priority.
As for needing a second motor connected, the video shows a single motor node and single controller. The empty RJ-45 connector on the motor node is for daisy-chain connection to additional motor node(s). A second motor node would certainly aid identifying which of the two parts are defective.
Since RS485 supports multi-point networking, each node is required to have a unique address.
Now the question becomes “how is the node ID set on each motor (DIP switches or EEPROM?) and has this particular motor lost its ID setting, or have an incorrect ID?”
Much time can be wasted studying the protocol only to find the problem extraneous. Also, it is not of much use to look at the controller, without the motor connected. How can one learn if the motor node is trying to reply with an error code, or garbage data?
More information about the specific application can provide additional clues and better guide troubleshooting.
RF+ Tech
Navigation
[0] Message Index
[*] Previous page
Go to full version