Accessories

Model 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 bps to 115.2 Kbps. 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.

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.

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.

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).

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 "A" terminal should be negative with respect to the "B" terminal. If your equipment uses a "+" and "-" naming scheme, in most cases, the "A" line will be connected to the "-" and the "B" line will be connected to the "+".

The 485SD9RJ is a port-powered, half-duplex RS-232 to RS-485 converter with send data control. The unit converts TD and RD RS-232 lines to balanced RS-485 signals and supports two-wire RS-485 communications only. The converter is powered from the RS-232 handshake lines, RTS, CTS and DTR, DSR, CD. The handshake lines are looped back on each other and can be in either state. No handshake change is necessary so no software is required to control the lines. The RS-485 driver is enabled with each bit of data. The RS-485 receiver is disabled when the driver is enabled and is enabled when the driver is disabled. This prevents data from being echoed back into the RS-232 device. The RS-232 side has a DB-9 female connector. The RS-485 side has a six-position RJ11 connector.

The 485TBLED converts unbalanced, full-duplex RS-232 signals to balanced, full or half-duplex RS-422 or RS-485 signals. RS-485 is an enhanced version of the RS-422 Standard. It allows multiple drivers and receivers on a two-wire or four-wire system.

The RS-232 port, configured as a DCE port, has a female DB25 connector with pins 2 (TD input), 3 (RD output), and 7 (Signal Ground) supported. Pins 4 (RTS) and 5 (CTS) are tied together, and pins 6 (DSR), 8 (CD), and 20 (DTR) are also tied together. Pins 1 (Frame Ground) and 7 (Signal Ground) are connected straight through to the RS-485 terminal blocks. The RS-485 terminal blocks support Transmit Data (A-) and (B+), Receive Data (A-) and (B+), Frame Ground, Signal Ground, and +12 VDC input. See Schematic.

These compact USB to Asynchronous Serial RS-232 and
RS-485 mini-converters allow you to add a serial port to your USB only PC. They are perfect connecting to a remote device to gather data or upload a program. USB 2.0 compatibility makes installing them on your PC easy. Versions are available with DB9 connectors and Terminal Blocks for quick wiring. We support RS-232, RS-485
(2-Wire) and RS-485 (4-Wire) protocols. Need 5 Volt and 3.3 Volt TTL? We even have a converter for that. Our driver software supports operating systems up to Windows 7 with 32 and 64 bit support.