delabs Circuits

Showing posts with label STC1000-Controller. Show all posts
Showing posts with label STC1000-Controller. Show all posts

Friday, May 01, 2009

RTD Pt-100 Signal Conditioning Module

This is the RTD Signal Amplifier part of Temperature Controller or Indicator. The card also contains a relay on-off control circuit.

The Circuits are -

The PCB Boards -

Wednesday, April 01, 2009

Proportional Module for Process Controller

When you need a proportional control output, either 4-20mA or Time Proportional On-Off, This module is used. It does a slow PWM control, the cycle time for SSR or Thyristor Banks can be closer to Mains Frequency. The 4-20mA can be used to drive motors for turning valves for fuel or fluid heat control.

Schematics of Module

Board of Module

Thermocouple and Current Input Module

This input module converts J, K Thermocouple and 4-20 mA Inputs to 0-2V Full Scale. These can be used for any voltage/current inputs too. The RTD module can be modified more easily for Voltage inputs. The control output can be On-Off or 4-20 mA/Proportional with another card. The 4-20mA I/O STC1000I is not complete in documentation.

This is a Input Signal Conditioning Card for the Temperature controller. The voltage levels from sensors are either too low or need to be translated in level and span. Then for greater accuracy some linearization methods have to be used for a more precise reading. This also increases the cost. The circuits here do no cover the linearization see others in this and my related pages.

The step or segment linearization can be done by transistor, diode or CMOS switches to accomplish varying attenuation/gain for stages of the curve or voltage levels. In Microcontroller systems it can be done by lookup tables or math.

In some older digital systems without a MCU, the A to D drives the address of an Eprom Array to get a Digital Data for Display, as a linearized Reading. This Corrected Data was in turn made into analog using a D/A and then on to a Chart Recorder. This was a Logic only System of the early days. Microprocessor systems was expensive, power consuming and use to frighten people by getting lost in loops or a short nap.(they have fixed that, make sure you code properly).

Input Module - J and K Thermocouple with 4-20 mA

Input Module - J and K Thermocouple with 4-20 mA

PCB Boards of the Module

Tuesday, March 10, 2009

Temperature Controller Main Card

This contains the Main card with a Power Supply and Relay Control. On this card is connected the Display ICL7107 - Temperature controller.

The Thermocouple and Control Modules can be plugged into this card, these change the type of control and type of inputs. This way this can be made into any parameter controller with any type of input and output. But it is all set in production, not configurable at site.

So even if you make a 4-20mA output Flow Controller with this, the Main card and Display card remains the same. Only the Modules change. No Connectors are used, to make it vibration resistant.

The PCB Layout is here

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