Hello,
I�m an engineer working to develop an underwater machine.
I have quite a bit of experience in software engineering but saying I’m a newbie in IO boards is an understatement…
What I need to do in my project is to control :
� 6-8 on/off switches
� 4/6 proportional controls
� read values from another 6-8 sensors
I need to communicate with this board at a max of 300 meters (1000 feet), and someone suggested that I should look into RS-485.
The speed of refreshing isn�t that important, specially because I am initially just looking for a board to learn to program and to run tests on.
Could you suggest what kind of board you think I should use?
Also, do you think that RS-485 is a reasonably communication protocol seeing that modern laptops often do not have a serial port?
I have done something similar to what you are doing many years ago, both ROV and subsea tooling systems. For the tooling system we successfully used the old Zworld controllers (BL1200 and XP8600 etc) that had a bus to connect them all.
I need a bit more information about the type of signals you want to interface to the controller to be able to offer a bit more help.
Is the proportional output PWM, analog or something else?
What is the switches you want to control? Input or outputs and what voltages?
For the sensors, what type of input? Analog, 4-20mA etc?
You could consider using one of the core modules along with a custom designed PCB for the IO. This is quite easy if you have the skills to do this or have someone who can do this for you. This is generally how I use the Zworld core modules to design my systems.
RS485 is ideal and you can use one of the USB to Serial interfaces to do this on a PC without a serial port. Have done it successfully myself. If you have the cores in your cable you could consider RS422 which is 4 wire and this will give you a duplex interface much like RS232. The advantage is no messing around with turnaround delays and half duplex on RS485.
Another option is to consider CAN bus. You can make a really nice modular subsea control system with that. You would need a serial or USB to CAN interface for the PC but there are a number of these. Interfacing CAN to the Zworld Core Modules is easy with either the Microchip MCP2515 or the Philips SJA1000.