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9.2.2. To Set the RS-485 Address:
In addition to the supply’s IP address, the multi-drop requires setting an RS-485 address.
It is viewed on the front panel of the power supply by setting it to local mode (see
section 3.1.1) and pressing and holding the REM/LOC button. The address may then be
changed by turning the voltage encoder
The default RS-485 address is 6. It may be set to any value from 0 to 30. The RS-485
address is not related to the IP address. However, it is required that no other power supply
on the multi-drop chain have the same RS-485 address
9.3. Connect and Configure the RS-485 Supplies
The RS-485 linked power supplies, at the tail of the multi-drop chain, are sometimes called the
Slave supplies. They may be individually commanded and queried using the LAN port on the
Master supply
The RS-485 power supplies must be Multi-drop enabled
9.3.1. To Verify the Multi-drop is Enabled:
A. Look for the “MD” symbol at the end of the bar-code in the product label.
B. Or try running the multi-drop chain. Open the LAN web page. On the DC Power page,
click the “Refresh List” control (see section 5.4.1). The addresses of all the multi-drop
enabled RS-485 supplies will be shown in the list
C. Or use the RS-232/485 port with a communication program such as HyperTerminal to
send the “MDAV?” query. if the response is “1”, the multi-drop is enabled in the supply.
Refer to the Technical Manual for details on using the RS-232/485 port
9.3.2. To Set Up an RS-485 Chain:
A. If the supply has the LAN or IEEE option, disable the option by sliding the LAN enable
switch to DOWN. See section 2.2.1 and Figure 3
B. Set the supply into RS-485 mode by setting rear-panel SW1 bit 6 to UP
C. Connect the RS-485 Link Cables from the master’s J3-OUT to the slave’s J3-IN
D. Power-up the supplies
E. Set the supply’s RS-485 address as described in section 9.2.2
F. While you are setting the address, also set the BAUD rate to 19.2K by turning the
current encoder
9.3.3. Optional RS-485 Terminator
For very long RS-485 cable distances, or if many supplies are chained together, a signal
terminator may added to improve signal integrity. The terminator is plugged into the J3-OUT
of the last supply in the chain (see diagram above).
To make a terminator:
A. Crimp a short cable to a RJ-45 connector (or just use the end of a LAN cable)
B. Use two ¼ watt resistors, recommended value is 120 ohms, and solder them:
from pin-3 to pin-6 (TXD+ to TXD–)
from pin-4 to pin-5 (RXD+ to RXD–)
C. Although the RS-485 bus should not be at hazardous voltages, insulate the terminator
properly for your application
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