Hello Arduino Community,
I am building my first bigger Arduino project at the Moment. Unfortunately I am not that much experienced with microcontrollers and so on.
My current project is to build a control panel with the Arduino that can control a certain number of devices. The interface for communication in this case is RS-485. I am using the SN75176BP from Texas instruments for this operation and already got everything working on a breadboard. I can send and receive commands over the rs485 bus, by changing the Enable pins of the IC to high or low depeding on if i want to transmit or receive with the arduino control panel.
The device only answers when it is asked to.
Please see the circuit i build for that here:https://dl.dropbox.com/u/5970471/transceive_rs485.jpg
Unfortunately i am not quite sure, if the circuit i build, is reliable. Thats because i have seen a lot of circuits with many resistors and transistors on the internet that doesnt really look quite as simple as mine. To be honest i do not really know what the 120 Ohm resistor between A and B does....
My goal ist to achieve a stable communication between the control panel and the controlled device at a baudrate up to 115200 and up to 800m distance.
I would appreciate very much, if you could give me your oppinion on this and describe in detail what i could improve here.
Thanks in advance and best regards,