Process Control (Page 2)

Industrial Automation and Process Control.

This is a prototype of a Preset Counter. It is built with ICM7217. The cabinet is ABS Plastic DIN 96-96. The Panel is Engraved on Acrylic.

I don’t remember for which application it was used. It has three thumbwheel settings, when the proximity switch counts upto the set-value, the corresponding relay turns ON, with a State Indicating LED on front panel.

Three Point Preset Counter

These can be configured sequentially or to work synchronously, this depends on what customer wants. Both modes may give the same result. In sequential operation, Some of these counters-timers may need to wait for an external trigger or feedback from a limit switch or another process like pressure alarm. Then more Input options may have to be provided.

Basic Electronic Digital Circuits

Counters, timers, analog-process and its interconnectivity makes up the various process loops or chain-reactions in Machine control. The various types of sensors for measurement and feedback of analog and event parameters, monitor the mechanical system and communicate the data to the process instruments.

The below circuit is a reference, i used the old intersil hot ideas book. There was no internet then. Databooks were valuable reference material. In the below timer circuit replace the clock with a schmitt trigger signal conditioning, it becomes a event counter or preset counter with thumbwheel input. See photograph above.

ICM7217 Timer and Counter

The Actuators like Drives, Solenoids, Pumps, Valves and Heaters act in accordance to the commands of the control system. This regulates and manages the process or machine to deliver consistent and repeatable yield of the end product.

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.

I will give a simple example for the purpose of understanding and assimilation of the concept. Consider the Toaster a Vital Home Appliance, Build a Embedded Internet Interface into the toaster. Then make it Wireless Networking capable. The gadget can also get connected thru Mains Carrier Communication.

Now you build a Webware service, create API’s, Ready Gadgets and Wizards. So he can create-use the API from any Computer or PDA. He can Sub-Lease his custom API Service with Internet capable Gadgets.

Make this a Web Toaster – When i made this post, the iGoogle was the reason behind it.

Make this a Web Toaster

When the Javascript of this is linked to the API of the Control Webapp that you created, This gadget can monitor and control the Quality of the Toast from anywhere in the world ;-).

Digital Timer for Internet – Live Widget

But Then, the service should be easy for just anyone to use, the coding is never done by the user of the service. He creates an account, hires the API, creates his own Gadgets and Apps with wizards. Then he gets to download the firmware for the Embedded Internet ASIC you Provide and the Product he manufactures goes with that circuit. See a Screenshot below

programmable-digital-timer

The end customer buys an Internet capable Toaster with a CD demo on how to access his free webservice. With this service, he can get all the web gadgets and tools to control his Home Appliance Arsenal.

Idea – 19:36 25-Feb-08, Nature – Open Source, – Ideas of delabs

More Reading –

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.