If you ever wanted to connect to device in the same building (e.g. to machinery on production hal) and to you have to go to it to connect your computer. We have a solution for you to resolve this issue, interface converters RS - 232 to RS - 485 first let's talk about some of the key advantages of RS-485 over 232. 485 is a single supply voltage, whereas RS-232 you require a 5 V and +/- 12 V. What RS-485 does, it just needs 5 V because it just swings over to 5 V at the output.

    One of the key advantages also is that RS-485 can drive data a long distance. It can drive things 1200 meters, which RS - 232 is about 15 meters maximum. And the 485 is also very fast. You’re talking about at least 10 megabits for the slow ones. The fastest RS-485 transceivers out there right now are running about 50 megabits. And RS - 2322 right now, the fastest transceivers right now are 1 megabit.

    One other key advantage that most people using 485 is, the better noise immunity. Because of the differential signal, any noise is subjected externally to the cable is basically subjected to both cables. So when you take the difference of the two, noise is actually canceled out. So it’s better noise immunity. So that’s one of the key advantages why people are using 485.

Fig. 1

    Some of the typical applications of RS-485 is point of sale equipment. You probably have used this many times at stores without realizing it. Those little price checkers that are kind of spread out throughout the store, you just bring your merchandise up there and just check the prices. That’s actually using a 485 transceiver in the box. When you scan the bar code, the information actually gets sent on a 485 transceiver through a long cable to a PC somewhere within the store. So this way not all the price checker needs to be uploaded with information. It basically goes to a remote PC that has all the pricing information and it sends the data back to you. And this way it’s easy for – one reason why they do this is that it makes it easy for the stores to update prices. They can easily update one PC, which will take care of all prices to the store. Plus a lot of times the data rates are so slow on these bar code readers because they’re only sending a few kilobits. So you’ll need to really have a high-end PC at each terminal to actually store prices. They just send it to remote PC and basically send it back.

    As shown in fig 1 computer is connected to the converter RS232 - RS485 ATC - 105. Converter is also connected to external power, supporting RS485 port. On the other side we also have converter RS232 - RS485 ATC - 108N, via the RS232 port is connected to cash or other device with RS232 port. Converter needs power supply for both ports RS232 - RS485

    The RS-485 application in heating, ventilation, air-conditioning unit. RS-485 is used in basically connecting the temp sensor or thermostat in the room to the master controller. If you’re sitting in the office right now, and you look to see your thermostat, there’s usually RS-485 transceivers connecting that from there to basically the control unit in the building. What it does is that’s after sensing the temperature in the room and yet when you’re making adjustment to the thermostat, it actually sends the data to the controller, which could be controlling that, the temperature, turning on and off the AC to heat or cool the room up. So that’s how RS-485’s being used.

    One of the main reasons why this standard is used it's because RS-485 is able to send data a long distance. RS-485 can send data 1200 meters on cable. So in your typical office building, you’re probably running hundreds of feet if not thousands of feet just from one end of the building to the next. Also, its robustness. It is a differential signal. So remember, differential, any noise subjected to the cable is canceled out. So you can have a reliable, low-cost solution to a heating, ventilation control unit.