About This Item
Overview
Details
OVERVIEWModel BB-485PTBR converts unbalanced RS-232 signals to balanced, full or half-duplex RS-485 signals. RS-485 is an enhanced version of the RS-422 Standard allowing multiple drivers and receivers on a two-wire system. The RS-232 port has a female DB9 connector with pins 2(RD), 3(TD), and 5(SG) supported. Pins 7(RTS) and 8(CTS) are tied together. Also pins 6(DSR), 1(CD), and 4(DTR) are tied together, but not passed through the converter. The RS-485 port has an 8-position pluggable terminal block connector.
BAUD RATE
Model BB-485PTBR supports baud rates from 300 to 115.2K. In order to change the baud rate, a resistor and possibly a capacitor must be changed. By looking up the selected baud rate on Table 1 the resistor and capacitor value can be determined. Remove R3 and C7 from the printed circuit board. Place new components in the R2 and C6 locations. See Figure 1 and 2 for resistor and capacitor locations.
BIASING RESISTORS
The biasing resistors R5 and R7 can also be altered. Model BB-485PTBR comes standard with 4.7K biasing resistors. To change the value of biasing resistors, remove R5 and R7 and replace with new value in locations R4 and R6. See Figures 1 and 2 for resistor locations.
TERMINATION RESISTOR
The termination resistor is located at R8. A termination resistor can be placed in the R8 location and a jumper wire placed from the terminal location to RD(B). B+B SmartWorx recommends a 100-120 Ohm resistor for termination. See Figure 2 for termination resistor location.
CONSTANT RECEIVER ENABLE
The BB-485PTBR is factory-set with the receiver disabled during transmission. It can be set for constant receiver enable. When R9 is removed, the receiver is in constant receive mode (four-wire). When R9 is in the circuit it is in half-duplex mode (two-wire). See Figure 1 for jumper location.
DATA LINE POLARITY
The polarity of the two RS-485 lines must be correct. With no data being sent, the RS-232 line should be negative and the RS-485 ìAî terminal should be negative with respect to the ìBî terminal. If your equipment uses a ì+î and ì-ì naming scheme, in most cases, the ìAî line will be connected to the ì-ì and the ìBî line will be connected to the ì+î.
Documentation
Features
- Converts RS-232 signals to RS-485 signals
- Extends data communication up to 1219 meters (4000 ft)
- Multi-drop capability - up to 32 receivers per driver
- Pluggable terminal block for easy wiring
- Data rate: up to 115.2 kbps
- Quick, easy inline installation
- 12 VDC power supply required (not included, sold separately)
