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Difference between RS232 and RS485
RS232 and RS485 both are the standard protocols of serial communication used to send and receive data. It is developed by the EIA (Electronic Industries Association) / TIA (Telecommunication Industries Association).
The main purpose of a serial interface is to provide a single path for data transmission wirelessly over a cable. A serial interface is a very good option for communications over any distance greater than several feet.
There are certain points at which RS232 differs from RS485, such as
- Communication Distance
- Immunity against electrical noise and ground
- Numbers of devices
- Data transmission speed
Specifications of RS232 and RS485:
| Specifications | RS232 | RS485 |
| Voltage System | Voltage-Level based | Differential |
| Total Driver and Receiver in one line | 1 Driver, 1 Receiver | 32 Drivers, 32 Receivers (Only one driver active at a time) |
| Line Configuration | Single-ended | Differential |
| Mode of Operation | Simplex of Full Duplex | Simplex of Half Duplex |
| Maximum Cable Length | 15 Mt or 50 Feet | 1200 Mt or 3000 Feet |
| Maximum Data Transmission Rate | 1 Mbits/s | 10 Mbits/s |
| Typical Voltage Level | ±5V to ±15V | ±1.5V to ±6V |
| Receiver Input Resistance | 3 to 7 kΩ | 12 kΩ |
| Receiver Sensitivity | ±3V | ±200mV |
Communication Distance
We can communicate a sender and a receiver over a maximum distance of 15 meters in RS232. However, cable length can be extended but with a slower data communication speed.
For RS485, the communication distance between sender and receiver is remarkably longer up to 1200 meters. That is far better than the RS232 and the could be the main reason to pick RS485 over RS232.
Immunity against Electrical Noise and Ground
RS232 operates on a single-ended line technique that performs well while using with a minimal ground potential. However, in electrically noisy environments with different potential levels, RS232 is too fragile and allows data corruption.
RS485 offers higher noise immunity as it operates on a differential-voltage system, which allows it a longer data transfer distance. Lower voltage use of RS485 offers a higher data speed.
Numbers of Devices
RS232 has only two devices in a network, one is a sender and the other is a receiver.
RS485 is designed for a multi-point system and it can connect up to 32 devices to a single transmitter.
Data Transmission Speed
RS232 can transmit data with a speed of 1 Mbit/s over a distance of 15 meters. While RS485 has a data transmission speed of up to 10 Mbit/s up to a distance of 15 Meter. Although it can transmit data up to 1200 Meter with a speed of 100 Kbit/s.
DB-9 PinOut Diagram
Applications
- Programmable Logic Controllers (PLC)
- Computer Numerically Controlled (CNC) Machine Tools
- Robotics Applications
- Embedded Control Computers
- Medical Instruments
- Power Measuring Instruments
- Printers and Scanners
Summary
RS232 has an advantage when short-distance and low-speed are required. It is a simple and low-cost interface. When you want a simple communication interface between two devices only, Two pins full-duplex communication can be easily established using RS232.
RS485 provides a higher speed over a longer distance, so it is used generally in a network with multiple devices up to 32 devices in a single network over a longer distance.
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