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Frequently Asked Questions - r. e. Smith Serial Communications RS485 RS232 RS422

by Son Eldred (2024-07-30)


Different Unit Loads in transceivers allow more devices on a network, including full, half, quarter, or eighth-unit load circuits. Here again, we start with including the standard library for driving the LCD and declare the D8 pin of the Arduino Nano as an output pin which we will later use to declare the MAX485 Module as a transmitter or Receiver. The SCK pin clocks the serial A/D’s CLK input which causes the A/D’s conversion result to be transferred to the master via the MISO line. While RS422 is comparable to RS485, it is limited to unidirectional data traffic, and is terminated only on the end of the line opposite the transmitter. The other devices (the slaves) respond by giving the requested data to the master, or by taking the action requested in the query. You probably have heard of RS232 which is a serial communication method between computers and devices , but have you heard of the RS485 communication? The RS485 standard addresses the problem of data transmission, where a balanced (differential) transmission line is used in a multi-drop (party line) configuration (or point-to-point if only two devices are on the network). Twisted pair wire with a characteristic impedance of 120 ohms is recommended with 120 ohm termination at each end of the communications line.


One reason is that, large networks accumulate distributed electrical noise which can make communications unreliable. While it goes against conventional wisdom, and can potentially cause a problem with circulating currents by grounding a shielded cable at both ends, this method is very effective at keeping induced lightening noise away from the communications lines. PTZ camera can pan and tilt to the required position and observe and/or follow target movements. Yes, we provide 1 year warranty for the vehicle ptz IP cameras. PTZ is an abbreviation for pan, tilt and zoom and reflects the movement options of the camera. R.E.Smith also provides an extensive line of optical/transformer isolated repeaters and multi-port repeaters as well as a series of fiber optic products which provide very high isolation. While the standard only supports low data rates and short line length (50ft.) it is still widely used and, very useful in many applications. Data rates of up to 10M bps are supported over short distances (40ft.). At the four-thousand foot distance limit, data rates of up to 100K bps are allowable. This was developed in 1962 when the need for forms of transmitting data from modems attached telephone lines to remote communications equipments became apparent.


Converters in general can be used to change the electrical characteristice of one communications standard into another, to take advantage of the best properties of the alternate standard selected. In general it is very important not to run communications wires in the same trough or conduit or in parallel with AC power cables. In general RS485 is designed for multi-drop, "daisy-chain" operation over a single twisted pair cable with a nominal characteristic impedance of 120 Ohms. The RS485 standard only specifies electrical characteristics of the driver and the receiver, it does not specify or recommend any protocol. The driver is limited for short-circuit current and the driver outputs can be placed at a high impedance state through the thermal shutdown circuit. The test setup we used for this project can be found below. The complete working of this project can be found in the video linked below. By using repeaters very large RS-485 networks can be formed. By "isolating" sections of a large network, the accumulated noise on one isolated leg is not so likely to cause a data error that will propagate to another leg of the network. Another potential problem with large networks without isolation, is that severe damage can occur to your entire system, if a high voltage source is connected (accidentally or otherwise) to your communications lines.


In this project, we have only used a baud rate of 9600 which is well under the maximum transfer speed we can achieve with the MAX-485 Module but this speed is suitable for most of the sensor modules out there and we don’t really need all the maximum speeds while working with Arduino and other development boards unless you are using the cable as an ethernet connection and require all the bandwidth and transfer speed you can get. Do play around with transfer speed on your own and give a try to other ethernet cable types too. Compatible with Worldwide LoRaWAN networks: It can be used with different types of LoRaWAN gateways and is compatible with multiple LoRaWAN Network Servers (Helium, TTN, etc). Even though some IC manufacturers offer light loading devices, that can accommodate 256 or even 400 nodes on one RS485 network, you may NOT want to build such a network for a few reasons. In the alternative, ground one end of the shield and connect the other end to ground through a bi-directional transient protector (from a few volts to a few hundred volts depending on the situation).



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