I am a Marine Engineer originally from ....., now residing in Australia. I am looking to modify a system that has 24V DC input to control 24DC solenoid valves and would like to go via solid state relays. The control inputs for the solenoid valves inputs are via 2 Kohm joystick potentiometers having -12V to 0 to +12V having a centre tap. Any thing you can tell me about how I can do this?
Mail from BD of AU
Do you need time proportional control of solenoids, or just on-off. If it is a Analog control from a linear Joystick, it is complex. If it just on-off solenoids on movement of joystick it is simple. use comparators to detect levels from joystick. the output of comparators go to a driver chip. The driver chip turns SSR on-off. Use an SSR which can handle the Solenoid current.
The original is analogue input signal from joysticks into a Siemens S5 PLC and digital output to solenoids. The Analogue modules have inputs from both jthe oysticks and feedback potentiometers. I would like to mimic this if possible and do away with the the PLC altogether and could look at other easier options. Can you provide any advice? How much would something like this cost? Much appreciate your help.
Mail from BD of AU
You could see this article from siemens SIMATIC S5-S7 Migration Support. This is a PLC, means an embedded system, it has a microcontroller and firmware. Users can program it with Visual Design aids like Ladder Logic on a PC Interface. The PLC then will work as a stand-alone unit, to manage a machine or process automation.
You can use another PLC to replace the existing system, Programming a PLC is very easy with the software that comes with it. A custom embedded solution is possible only after understanding the entire process on which this PLC was used. Which is not just the PLC and Electrical Components but the process control logic and learning that goes inside. A custom solution may be expensive if it is just for one machine or process.
Are you going to use it in a OEM kind of application for manufacturing of some industrial systems? Then a custom solution is feasible, as the cost is amortized over the many control units that are made. If it is repair and maintenance then just use the SIMATIC upgrade instructions above. Siemens Australia & New Zealand
....... We are only looking to drive a winch on our ship which is basically controlled by a set of 22 solenoid valves in differnet configurations. The S5 PLC we have is 22 years old and don't really see the point of migrating to S7 at the cost for what we need to be able to do as the ship is so old already. At any one time only maybe 3 or 4 are energised so basically quite simple so I can't see why we need a PLC at all. I'm sure that if I gave you all the information you could tell me how to do it in a matter of minutes. .... .... ..... as knowledgeable as you are with these systems but believe we don't need a PLC at all. Any help you can give me in setting up a system to control 6 sets of solenoid valves from 2 joysticks.
In one mode each joystick operates 3 individual solenoid valves each In another 1 joystick operates all the valve while the 2nd joystick is disabled. Other 16 solenoids are mostly operated by individual On / Off switches. Must be quite obviously simple to do this for you, so any help will be much appreciated.
Mail from BD of AU
Much as i would like, i would not like to take up such work now.
I think a person who can make a cost effective solution is jotech.no. This firm in australia may make a nice solution airborn.com.au
Contact me for anything you need to know, i would still insist that a PLC is better. We cant take any chances with ships, it is a risk, make a robust solution.