Saturday, March 29, 2008

Digital Count-Up Timer Gadget

Here is is Digital Timer Learning Gadget. The buttons make a sound and Light up internal LED lamps. Power On-Off control, Digital Timer; Start, Reset Scroll and Select are the controls. This will simulate the operation of a microcontroller based digital timer.

Project Page programmable-digital-timer

Press The Power on-off for a soft start, this is to prevent the inrush current from stressing the javascript components. Then it goes to a display test. The Start button can run or stop timer by toggling. The reset will Bring timer to 0000, format is min-sec.

Set by pressing select to get a marker over orange digit, Use Scroll to set number. Press Start to start timer, Start to be off to set again. The buzzer will turn on when Time elapsed matches time set. and the alarm relay trips. And a Flashing Annunciator signals end of process. Now Reset will start process again and stop flashing LED.
Digital Count-Up Timer Gadget

To use this like a regular instrument, you need a small portable hand-held computer with browser. Fix that in a Cabinet by filing or grinding it to size and wire the relays and supply. :-)

Thursday, March 27, 2008

Learn Digital Logic Gates Operation

The Gate is a digital component that is used to compute an output for certain inputs, the inputs and outputs have two states high-1 and low- 0. Let us assume high is 5V and low is 0V (like in CMOS). On a high level the LED will light up and on a low level the LED is off. Now let us see what Logic means. digital-tutors - project page.

This page requires images and javascript to be enabled to try out the demo of the gates below.

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Digital Logic Gates

Gates are what make many of ICs, the two popular families are the 40xx CMOS and the 74xx TTL . Now 40xx come in 74HCT40xx flavors which approach the quality of an ideal gate. Entire circuits with Gates can also be also be burnt into PLDs, FPGAs and CPLDs just like you burn your CDROM. Gates can also be implemented in assembly language which a microcontroller like 8051 will understand and execute.

Hardware gate circuit will operate in real time, nano seconds delay will be there due to propagation delay, gate capacitance and FET switching times etc. Software or microcontroller gates code working will depend on both propagation delay and the CPU clock speed.

Gates can be combined to make combinational or sequential logic circuits. combinational circuits are a complex network of gates interconnected to evaluate a pattern of output for patterns of input. Sequential circuits use memory elements hence output patterns depend both on input patterns and the memory of history of events. An example of combinational logic circuit is a seven segment display decoder CD4511 and and example for a sequential logic circuit is CD4029 up-down counter.

The CD40xx CMOS family can work at even 3V-9V-12V DC and consume low power. The speed is not as fast as 74xx TTL family. It is good for simple portable battery powered circuits. The 74HCTxx series is good for low power and high speed but will work at 5V. When you have problems interfacing CMOS and TTL use 74HCTxx family.

Tuesday, March 25, 2008

DC Circuits - University of Guelph

DC Circuits - University of Guelph
  • Schematic Diagrams
  • Complicated Circuits
  • Ohm's Law
  • Kirchhoff's Current Law
  • Kirchhoff's Voltage Law
  • Resistors in Series
  • Resistors in Parallel
Physics Tutorial Menu - Unit Conversions

Tuesday, March 04, 2008

Megger or Insulation Tester

Decades ago, when a customer found that my Tera Ohm Meter expensive, He suggested the specs for this low cost scaled-down model. This was found useful for people sub-contracting Telecom Equipment Manufacturing.

Insulation Tester

Test and Measurement Instruments

Monday, March 03, 2008

Heater for Heating Chambers

This was a Heater which was custom built for a CRT manufacturer, It is comprised of many Tubular finned heaters. And probably a big fan that worked at high temperatures. This was used in a Heating Chamber which aged or tested CRT monitors. It had a temperature controller, a remote indicator.

CRT Chamber Heater

Industrial Automation & Process Control

Multi Zone Temperature Controller

This is a Multi Zone Temperature Control panel used in Plastic Extrusion Moulding. We made many of these and it helped us learn cable management techniques. The panel is a standard way it was built and some of the merits were the selection of panel components and wiring expertise.

Multi Zone Temperature Controller


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