RS232 to RS485-Optical Isolated-CQDT9015

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  • The RS232 to RS485 converter of CQRobot provides industrial grade isolation with fairly resistant to noise. It is an optically isolated and protection type converter, separating the data lines inside the unit, this prevents noise, high voltage spikes, surges and ground-loops from damaging your computer or the equipment you have connected to the converter that can greatly improve the signal conversion efficiency, and protect the ends of equipment.
  • This converter is port-powered, you should in most cases be able to communicate up to the specified 4000 feet (1200m), however adding a terminal resistor can interfere with this distance because it increases power consumption. If you need it as your case may be, the pin of VCC allows you to connect a 9V external power supply to it. Therefore, you will get the maximum transmission distance: 4000 feet (1200m) (RS-485); 50 feet (15m) (RS-232).
  • This product is with universal DB9M/DB9F adapter plugs(DB-9 Female RS-232 end; DB-9 Male RS-485 connector). The standard DB9 connector is useful when using any type of new and old serial RS485 device. *Its output comes with a terminal block, which is connected with twisted pair or shielded cable, making it quite convenient for either connection or dis-assembly.
  • It has LED lights for indicating RX/TX data flow, very helpful when troubleshooting.
  • The built-in high sensitive receiving circuit to enhance the weak signal amplification. With fast Transient voltage suppression protector (TVS) to protect RS-485 device.
  • The unit is passive, therefore, normally no external power or flow control is required.
  • The circuit is with built in auto transceiver and anti-collision I/O circuit automatically controls data flow direction, these ensure the program written in RS-232 mode can be safely running in RS-485 mode without having to change, it fit for the existing software and hardware interface.


  • The RS485 Port provides data collision protection control DCPC function
  • OPTICAL ISOLATION, effectively avoid signal interference
  • Effectively prevents the destruction of both ends of the electric equipment
  • Adaptive selection of baud rate
  • With TX and RX LED indicators
  • Up to 32 nodes supported
  • RS-232 port protection: 15KV ESD
  • 600W lightning surge protection in RS485 port protects from Electrical Surges and Lightning Strikes
  • Bi-directional transformations of RS232 and RS485 signal



  • Computer
  • DVR monitor
  • Terminal devices
  • Door safe system
  • SCADA(Supervisory control and data acquisition)
  • Building automation
  • Check on work attendance
  • Measuring instruments and monitoring system
  • Other devices with serial interface


  • Interface characteristics: Compatible with EIA/TIA RS-232C, RS485 standard
  • Connector Type:: DB-9 Female RS-232 end; DB-9 Male RS-485 connector
  • Working mode: Asynchronous half duplex
  • Transmission medium: twisted pair (diameter greater than or equal to 0.5MM) or shielded wire
  • Transmission rate: 300-115200 bps (115.2 Kbps)
  • Operating Environment: - 86 ℉ to 158 ℉ (relative humidity of 5% to 95%)
  • Max transmission distance: 1200 meters (RS-485); 15 meters (RS-232)
  • Protection class: 600W surge protection of each line of RS-485 interface
  • Isolation Voltage: 2500 VRMS pulse or 500V DC continuous
  • Two kinds of communication: point-to-point/ two wire half duplex; point to multipoint / two wire half duplex

Note: In order to prevent signals from reflection and interference, it is recommended to place a terminating resistor (parameter 120 ohm 1/4W) in the circuit of terminal, as the case may be.


Connector and Signal


Hardware Installation and use

This product is with universal DB9M/DB9F adapter plugs. Its output comes with a terminal block, which is connected with twisted pair or shielded cable, making it quite convenient for either connection or dis-assembly. T/R+, T/R- stands for receiving / sending A+ B-, GND stands for Ground. VCC stands for Positive Supply voltage. For RS-485 half duplex communication mode, the "T/R+" wire should be connected to the "A+" line, the "T/R-" wire to the "B-" line.

Communication Connection

  • Using the direct connections method, please make sure positive electrode connected to positive electrode and negative connected to negative; Ground generally do not need to be connected, in addition to some ground equipment.
  • If the interference is serious, can use 120 ohm 1/4 watt resistor is connected to the AB line; But it is not need if the signal is normal.

  • Generally no more than 32 terminal limit value with the support of RS485 multi machines communication. For twisted pair, it is better to use 24AWG (0.51mm) gauge to ensure the communication distance.

  • If you need to run RS232 signal over long distance, you may use two pieces of the adapter to make a connection directly, and please make sure the RS232 ports of two devices you connected are standard RS232 port; Because of this converter needs to take power from RS232 port, so standard RS232 port of your equipment is required. It will lead to communication failure if there is insufficient voltage. The solution is connecting an active DT-9016 and the other end connecting a passive CQDT9015.



Communication Failure

  • Check the RS-232 interface wiring is correct or not.
  • Check the RS-485 output interface wiring is correct or not.
  • Check and make sure the wiring terminal is connected well.

Data Missing or Wrong

  • Check the data communications equipment, data format is consistent rate.

Communication Barrier

  • Add a resistor in the last line of the 485 terminal. Add a resistor in the last line of the 485 terminal, or using an active converter to replace.