ZP485 Converter
Ing. Büro S. Ludescher, CH-Oftringen
Technical data of the RS485 converter ZP485
The ZP485 is a RS232 to RS485 converter which does not require a power supply. The power is dereived from the RS232 signals. It can be plugged directly onto the RS232 connector of the PC. Both, the RS232 and the RS485 connections are made with a 9-Pin D-Shell female connector. It works up to 115 kBaud. The DTR signal must be present all the time to power the receiver. To transmit data, the RTS signal must be set to high level.
Two versions are available, full duplex (ZP485F) or half duplex (ZP485H). The half duplex version additionally controls the receiver using the RTS signal (RTX high = transmit, low = receive).
Auxiliary power:
It depends to the impedance of the RS485 as well as to
the transmit bandwidth, whether an auxiliary power is
needed. On a impedance of 120 Ohm, the power lasts for 10
ms only (18-21 bytes at 19200 Baud). Then it needs a 15
ms pause. On a impedance of > 300 Ohm, no auxiliary
power is required.
The auxiliary power is a Voltage of 5-16 VDC and 25 mA is applied to pin 1(-) and 4(+) of the RS485 connector.
Diagram of the ZP485F: |
Diagram of the ZP485H: |
Transmit trough table
| RS232 Input | RS485 Output | |||
| DTR | RTS | TxD | TX+ | TX- |
| H | L | X | Z | Z |
| H | H | L | H | L |
| H | H | H | L | H |
L = Lo, H = High, X = Don’t care, Z = High Impedance (>3500 Ohm)