Sig- line. The RS485 receiver compares the voltage difference between both lines, instead of the absolute voltage level on a signal line. Sig- lines are twisted.The image below explains why. It is the reason why RS485 is so popular with computers, PLCs, micro controllers and intelligent sensors in scientific and technical applications. Network topology is probably the reason why RS485 is now the favorite of the four mentioned interfaces in data acquisition and control applications. That is why RS485 is currently a widely used communication interface in data acquisition and control applications where multiple nodes communicate with each other. The Solar Charge Controller has an Ethernet RS-485 communication interface as well as a USB cable. The "2-wire" RS-485 connection is shown below. In the picture above, the general network topology of RS485 is shown. In the picture above, noise is generated by magnetic fields from the environment. Shielding-which is a common method to prevent noise in RS232 lines-tries to keep hostile magnetic fields away from the signal lines. The magnetic fields are allowed to pass, but do no harm. We also see that the maximum allowed voltage levels for all interfaces are in the same range, but that the signal level is lower for the faster interfaces.

Because of this, the resulting noise current is many factors lower than with an ordinary straight cable. But You stated you are going to install this at a commercial setting, so it always better to use the worst case environment situations, rs485 cable and use shielded cable. This is, because on the other interfaces the communication channel is shared by multiple receivers and-in the case of RS485-by multiple senders.RS232 has a separate communication line for transmitting and receiving which-with a well written protocol-allows higher effective data rates at the same bit rate than the other interfaces. Because there is a chance of data collosion with this implementation, theory tells us that in this case only 37% of the bandwidth will be effectively used. Noise is easily picked up and limits both the maximum distance and communication speed.With RS485 on the contrary there is no such thing as a common zero as a signal reference. The maximum slew rate also limits the maximum communication speed on the line.For both other interfaces-RS422 and RS485-the slew rate is indefinite. First of all we see that the speed of the differential interfaces RS422 and RS485 is far superior to the single ended versions RS232 and RS423.We also see that there is a maximum slew rate defined for both RS232 and RS423.

Here’s what you’ll need to make your own USB to RS485 cable: - USB cable - DB9 connector - RS485 transceiver - Wire - Solder - Heat shrink tubing The first step is to solder the RS485 transceiver to the DB9 connector. With such an implementation of a RS485 network it is necessary that there is error detection implemented in the higher level protocol to detect the data corruption and resend the information at a later time.There is no need for the senders to explicity turn the RS485 driver on or off. Without termination resistors, signal reflections off the unterminated end of the cable can cause data corruption. See the sections on termination and biasing for more information. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. This means that in a master/slave configuration, a master can talk to multiple slaves, all of the slaves can talk back to the master, and every device on the network can hear every other device.

If distance between router and master inverter 80m, then use extender or repeater. Depending of the information in the sent data, zero or more nodes on the line respond to the master. The RS485 network must be designed as one line with multiple drops, not as a star. For higher speeds and longer lines, the termination resistances are necessary on both ends of the line to eliminate reflections. The combination of the cable impedances and/or termination resistors will load the network and can make communications unreliable. Termination resistors will reduce the amplitude of this reflection back from the ends which will improve the signal quality. With RS485 communication distances of 1200 m are possible.Differential signal lines also allow higher bit rates than possible with non-differential connections. 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. Since data rates on a PC serial port can vary from 300 baud (26mS for 8-bits) up to over 100k baud (0.08mS for 8-bits), the timer will have to either be limited in the baud rates that it can work with, or keep control of the RS-485 network for much longer than it needs.