Process Control (Page 2)

Industrial Automation and Process Control.

Proportional Controllers not only save energy, they can give a controlled finish or treatment to a job. An on-off controller or thermostat limit protection has to be used in series, this is to to stop a Runaway Process.

control system design

There was a real life instance when a Temperature cycling oven maker (environment chamber), faced large liabilities as an 8086 based profile controller and chart recorder just locked up and all the electronic equipment were roasted. Here even a bimetallic thermostat would have saved the day. Nowadays we have a watchdog timer to prevent such uP mishaps, but still use an analog controller in series as an over temperature trip.

Other Reading

The basics of control system design: Part 1 – Moving beyond PID

“This series of six articles will explore the use of six variations of P, I, and D gains: Proportional Control, Proportional-Integral Control, Psueodo-derivative feedback with feed-forwared (PDFF), PID control, PID+ control, and Proportional Derivative Control.”

These are the circuits and boards of a Mini Temperature Transmitter for a Platinum hundred ohms temperature Sensor.

Transmitter RTD

The customer wanted a two wire system, this needs low power opamps which were ten times the price. If this transmitter works at 3mA it could have been two wire. Those parts were in short supply and the budget of customer was low. So i made it with regular opamps but three wire. The customer was satisfied as he got a cost effective solution. But now the situation of markets and products are different.

RTD  Three Wire Transmitter

If you need to transmit the temperature from a high voltage area or toxic environment. You will need to hermetically seal the transmitters, convert the Voltage to frequency, frequency to IR LED flashes or RF. This can be then remotely monitored. Then the transmitter has to be battery-solar operated, low power too. ICL7135 is a simple solution. It has a serial output that can be used to Drive IR Leds. Remotely sense these flashes in a Micro-controller and you have a reading. You may be able to use optic-fibers too. Where volatile liquids are present so that the risks of sparks can be eliminated.

3 Wire Transmitter RTD

More at Process Control Circuits

This is the same Mini RTD Pt-100 Transmitter but in its case. Encapsulated in epoxy, hermetically sealed against harsh industrial environment. This will work well even near fumes of Ammonia with no corrosion. But not near vapors which can be ignited by sparking as terminals are still open. The side view shows zero and full scale ten turn bourns trimpots heads, for calibration. After cal it can be sealed with RTV compound.

Automation and Control is the predecessor of Robotics. A Jump Start, Practical and standard reference for Process Control is at at Omega Technical Reference.Tacho Counter

A Control system is made of Sensors sending acquired data to a Controller which operates Actuators to manage the process in Real Time. Starting from a Bimetal Thermostat to a SCADA, the controller has grown from mechanical — electrical — analog — digital devices to microcontroller-computer based equipment.

Both in Control Systems and Robotics the Collaboration between Robots or Control Units, leads to the development of wireless network of Interactive, Intelligent and Distributed Self Governing Systems. The outcome is Web Process Automation, Web Applications based Solutions in Monitoring, Analyzing and Configuring these Sophisticated Networked Systems.

Read More at my – Industrial Process Control Applications

This is a RTD Pt-100 Transmitter, It can Convert Thermocouple mV or RTD mV to 4-20 mA Current Transmitter. The part numbers on Circuit and silk screen may not match. But the PCB may be usable. The output is a current source and not a current sink. It goes to a 4-20mA Mux with a common ground. The Circuit RTD-Pt-100-Transmitter Circuit.

RTD Transmitter 4-20 mA

This low-cost transmitter was made to send RTD information in a 4-20mA over long distance. The 4-20mA was the input to a Analog-Mux which interfaced to a GE-Fanuc PLC system and a 486 Computer. The Analog Multiplexer Built around CD4051 was was controlled by PLC to get data from numerous channels. This reduced the cost of the System. This is ok when Real-Time Acquisition is not required. The Analog 4-20 to 4-20 Mux-Buffer circuit can be seen at Industrial Process Control Circuits.

This was done as customer budget could not afford dedicated analog input modules for every channel. There were more than 50 Inputs. The thermal inertia of system did not need a real time or fast correction.

The PNGs of PCB is 600dpi 16 color. It is to be scaled appropriately.

ICM7217 is a four digit, presettable up/down counter with an onboard presettable register continuously compared to the counter. The ICM7217 is intended for use in hard-wired applications where thumbwheel switches are used for loading data, and simple SPDT switches are used for chip control.

Digital Timers, Counters and Clocks has some of my designs using chips like this.

This circuit provides multiplexed 7 segment LED display outputs, with common anode or common cathode configurations available. Digit and segment drivers are provided to directly drive displays of up to 0.8 inch character height (common anode) at a 25% duty cycle. The frequency of the onboard multiplex oscillator may be controlled with a single capacitor, or the oscillator may be allowed to free run. Leading zeros can be blanked. The data appearing at the 7 segment and BCD outputs is latched; the content of the counter is transferred into the latches under external control by means of the Store pin.

See an Application of 7217 as a Preset Counter which is used in Process Control

ICM7217 Preset Counter

Features of Chip

  • Four Decade, Presettable Up-Down Counter with Parallel Zero Detect
  • Settable Register with Contents Continuously Compared to Counter
  • Directly Drives Multiplexed 7 Segment Common Anode or Common Cathode LED Displays
  • On-Board Multiplex Scan Oscillator
  • Schmitt Trigger On Count Input
  • TTL Compatible BCD I/O Port, Carry/Borrow, Equal, and Zero Outputs
  • Display Blank Control for Lower Power Operation; Quiescent Power Dissipation <5mW
  • All Terminals Fully Protected Against Static Discharge
  • Single 5V Supply Operation

delabs Notes-

This is another Intersil Masterpiece in days when using uP was complex and uC was not available.A 8085 could be used but with many supporting chips and it consumed power. This was a CMOS innovation low on power and just one ASIC had the fexibility for many digital operations.A ThumbWheel and Display Interface completed a Gadget.

CAN (Controller Area Network) is a serial bus system, which was originally developed for automotive applications in the early 1980’s. The CAN protocol was internationally standardized in 1993 as ISO 11898-1 and comprises the data link layer of the seven layer ISO/OSI reference model.

CAN Controller Area Network in Automation

CANopen is a CAN-based higher layer protocol. It was developed as a standardized embedded network with highly flexible configuration capabilities.

In the year 1992, several companies founded the CAN in Automation (CiA) non-profit group, in order to provide technical, product and marketing information.

CANopen-based dust-filtering systems

CANopen-based dust-filtering systems

Hesch (Germany) has developed an industrial dust-filtering systems. The HE 5750 host-controller provides a CANopen NMT master interface to communicate to the sub-layered valve units operating the dust-filters. The entire system can be controlled by means of the Profibus or Modbus interfaces. The embedded filter control software supports the reduction of emission values and energy costs.

The valve controllers are uses to pulse solenoid valves in industrial dust extraction technology. They are controlled via an embedded CANopen network by means of the HE 5750 host-controller. The NMT slave units are attributed locally and technically to one filter chamber each. This concept adapts to any desired number of filter chambers and valves.

CAN in Automation (CiA)
Kontumazgarten 3 DE-90429 Nuremberg, Germany.

This was one unique custom design i made for a Mining Company for Ore Processing. It was Multi Zone Scanner controller.

Multi Zone Temperature Controller

It might have been for a rotary kiln of a large size. Four temperature sensors were connected to the system with brushes just like in a motor. Even the supply to the trasmitters was on the brushes.

The Instrument had a Analog Multiplexer with a Synchronous Sample and hold, as the analog value was coming via the brushes. It had four relays that would turn off or on every scan cycle, depending on the input values. The kiln system was slow it had inertia, so it did not require a fast acquisition for ‘Real time’ as you may find necessary in small Thermal Systems.

This was built with analog and digital chips, no uC in this design. This was because it was a front end controller, there was a risk of a uC system getting stuck. These days, that problem may not be so worrisome, but i am not so sure.

What if the watchdog goes for a short nap?

You can find part of the designs here – Industrial Process Control Circuits

In 1876, Thomas Alva Edison opened a new laboratory in Menlo Park, New Jersey. Out of the laboratory came arguably the most famous invention of all-a practical incandescent electric lamp. By 1890, Edison had organized his various businesses into the “Edison General Electric Company.”

General Electric Company – GE

General Electric 40W light bulb.

General Electric 40W light bulb.

“Charles Proteus Steinmetz, already a distinguished industrial scientist, was hard at work as GE’s chief consulting engineer. After years of persuasion, Steinmetz convinced the GE leadership that the company would need a research laboratory to maintain its edge in lighting and electricity and also finding new areas to grow.” – Heritage of Research

Charles Proteus Steinmetz

Charles Proteus Steinmetz He made ground-breaking discoveries in the understanding of hysteresis that enabled engineers to better design electric motors for use in industry.