Ship Automation and PLC Technology

A Mail Thread from 2008, has been posted here. This is to enable students and engineers understand : The needs in in Maintenance Automation or Marine/Ship Automation. I could not take up this task as my engineering designs are only on paper, I used to take up automation projects, a decade back, not anymore. This feedback is also to enable product designers to create a ready configurable solution for Maintenance Personnel..

I would like to suggest that - A Simple Configurable (No Programming Knowledge, Graphical Drag-Drop more like an iPhone app) Automation Solution is required with a Magic Control Box with I/O. Affordable, Limited Functions. Where budget is squeezed and a temporary solution is needed. Even as a emergency standby solution.

delabs

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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

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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.

delabs

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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

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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 .

Here are people who can help you Siemens Solution Partner Contacts

delabs

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....... 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

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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.

delabs

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Temperature Meters with Analog Recorder Output

I would like to know if you offer a monitoring solution that will constantly measure ambient (air) temperature (say, 0 to 150°F), and provide a corresponding DC voltage output of either 100 mV, 1 V, 5 V, or 10 V. Do you make a unit that can be configured to do this?

Mail From JPE - WV - US

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Analog outputs were very popular as they are inputs to Strip Chart Recorders, Later they had an extra use for PC Based Data Acquisition, data Loggers and PLC. Now we have Instruments with digital and wireless outputs too.

Temperature Meters - DP116 - Omega

Economical 3/64 DIN panel meter that has a full size 0.56" green or red LED display, with a built-in analog output and display hold capability. 3 1 /2 Digit Display.

Features Include

• Thermocouple and RTD Input
• Full-Size 0.56" (14.2 mm) LED Display
• Analog Output Standard
• 1 /8 DIN Panel Adaptor Standard

Economical Digital Meters DP18 - Omega

The DP18 series is a complete family of panel meters with input cards for voltage, process and temperature measurement and control. The signal conditioners for voltage will measure ac or dc voltages or true RMS.

Modular Design, Options for Alarms, Analog Output of Communications, 3 1/2-Digit LED Available in Red or Green Displays

delabs

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Winding Insulation Resistance Measurement

I am working in power plant. we have a problem on one of gas generator. the problem is that low winding insulation resistance of generator rotor. it read 800 k ohm where the other generator read greater than 10 M ohm. at full speed, there is no Kv measurement. same time no standing alarm from excitation system. all equipment are indicated okay.

My question is that is the relation between low isolation resistance of generator rotor and Kv measurement?

Mail from - IB SA Arabia

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There is no relation between insulation resistance and any other parameter of you system. Insulation Resistance depends on age, physical damage on windings, humidity, contamination, wear and tear.

Let me know where you are doing the KV measurement. If you are measuring leakage voltage due to insulation breakdown, you have to fix it. The relationship of parameters does not matter. Small leakages can be tackled with grounding, don't compromise on safety and quality.

It is possible you may be touching one of the probes when you measure insulation, that may be the 800K, Even if one finger touches the probe, the circuit is closed via earth and a low 1M measurement can be seen.

The rotor the chassis all need to be grounded, and insulation resistance has to be measured after all power connections or electrical connections are removed. The electrical terminations unit should float for proper measurement, especially when you have doubts.

Tell me about your progress.

delabs

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I did not get a reply later, but i may not have understood the question well. The question also lacks details. In HV breakdown measurements KV is applied, but it has to be done after disconnecting all points. Beyond a limit, HV testing becomes destructive. Leakage Monitoring and Earth Leakage Breakers can be used. Motor/Generator Protection Units too. Even an imbalance in the current or Three phase problems.

It is best to use a Insulation Tester to apply little above Normal Voltage and see leakage, if this is a routine quality check. Better still, have a current sensor on the earth line and use a data logger to keep a tab on the leakage levels, temperature and voltage of all motors and generators. Even sound/vibration sensors will be an advantage. Before these electrical equipment fail many symptoms can be caught by data logging and limit windows. An electronic instrument or Trip Circuit will operate or alert after a fault occurs. Data logging and analysis will warn of a possible Motor or Generator performance degradation. Symptoms Indicate problems, prevention better than cure. Data Recording, Graphs and preemptive measures better than Breakdown Repairs in the Night. Drop in efficiency is an indicator for maintenace, This also prevents mishaps and power wastage.

It is true some insulation faults will show up on vibration and high humidity levels. These have to be simulated. In operation testing has to be done with sensors and recorders for leakage current etc. not insulation resistance.

Learn more about Insulation testing

• Technical Documentation - Megohm meters/Insulation
• Insulation Resistance Theory - doc00030

- delabs

Isolated RS-232 Serial Port Interface to SBC

Subject: Help!
Date: Thursday, December 16, 2010, 4:40 PM
Hello delabs
I have question about one your project . The question is about the project RS232 with Opto-Isolation on schematics.dapj.com. I need this very much . Do i need to use max 232 or something else on uC side , or i connect directly on uc rxd/txd pins .I need this answer so much , im new in this . please help

Best Regards

Mail from SS (CC) - Russia

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This was done when MAX232 was not invented yet. This interfaces with PC well. If you want to make a PC based datalogger with 80C31, then this gives a safe PC to 80C51 SBC Serial Link.

Suppose a Temperature sensor or a Heater Open up. If the High Voltage reaches the A/D and SBC. The PC will be next Victim.

The Affordability and Product Safety Aspects, Including Fire Hazards; made me use this, as any other solution would make product expensive. An Opto-coupler and well designed PCB can give more than 2 KV isolation.

The MAX232 does not have isolation, but look here Isolated RS-232 Transceivers. The MAX232 also generates a Higher Voltage level, like 10V for proper RS232.

The circuit i have made is very old and you can interface any serial uC with PC. No other chip is needed. It is cumbersome to build it and get it working for many. I suggest use one of these chips from Maxim unless you want to Adventure like me.

delabs

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Long Duration Linear Sweep or Ramp Generator

I hope you can help me with a circuit. Its a voltage sweep circuit that will sweep from 0v to10v in a 45 min time period, I'm using it for an input on a signal generator to control the output frequency.

I have tried a constant current source charging a capacitor but it just didn't seem to be solid. If It can be done digitally would be great! I have been struggling to do this and its the last part of the piece for my project.

Mail from CB in NA

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I have once answered a similar question. Ramp Generator Elex Quna.

You need clock pulses driving a counter, which operate a digital potentiometer. Or any D-A convector - or R-2R circuit. Say you need 1-10V in 45 mts. You first figure how fine the ramp needs to be, like resolution of 100mV?

The constant current may not work as the capacitor may leak and it may not be a perfect ramp. The cc ramp is good for 1 second or less.

A staircase ladder ramp is best for you, define every step of ladder as say 10 or 100mV. A clock of 1 Sec is given to a counter, binary counts, and the digital output of counter goes to D/A Convertor.

If you wish to use a PIC, AVR or 8051 uC, then use it to time and control a built in D-A convertor or PWM. This is done in the code or firmware.

• Applications in PIC Designs
• Maxim - Products - Digital potentiometers

So .... clock >> counter >> digital to analog >> Ramp = you got it. You can implement in both software or hardware, it is your choice.

delabs

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