TEE BLOG

May 17, 2012
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Op amp comparator tutorial and clapper circuit

Comparators are a very handy circuit block that everyone should know. The basic idea is that you have a reference voltage, and as your input goes above or below that voltage, the output of the comparator goes high or low. In the video I give an example clapper circuit that toggles an LED on and off based on the volume of sound in the room. You can extend the concept to use comparators to toggle any device you want whenever a voltage exceeds a certain threshold.

May 17, 2012
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Exploding electronic components!

May 13, 2012
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Multivibrartors [swf]

In this animated object, learners examine three different types of multivibrators: astable, monostable, and bistable. A brief quiz completes the activity.

May 12, 2012
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Capacitive touch sensing with a single ADC pin

Capacitive sense buttons and pads are awesome, but many of the available systems are either propitiatory or require a dedicated IC. Toumas decided to code his own based on a closed source Atmel example where a single ADC pin is used for capacitive sensing. He reverse engineered it, and documented his results:

I’ve been thinking of a project that needs a little bit more elegant user interface than your usual push buttons. Partly inspired by a video blog on Dave Jones’ EEVblog, I decided to look into capacitive touch buttons. The big issue unfortunately for me was that you usually need a separate chip for capacitive touch sensing. With some tricks, you can however use a normal microcontroller to do the job. Even using only a single pin and resistor.

I’ve got a full writeup of the experimentation on my website, including my understanding of the theory of operation and code (and a video of the board in action, the three buttons controlling the three colors of an RGB LED):

A lot of these techniques are riddled with patents, so watch out if you plan to sell your hardware.
http://tuomasnylund.fi/drupal6/content/ … le-adc-pin

May 12, 2012
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Programming dsPIC MCU in C

Learn how to write a program on your own, how to debug it, and how to use it to start up a microcontroller. The book provides numerous practical examples with necessary connection schematics explaining the operation of temperature sensors, A/D and D/A converters, LCD and LED displays, relays, communication modules etc. It is constantly updated with fresh examples. All program codes are commented in details to make it easier for beginners to start programming. Instruction set, operators, control structures, and other elements of the C programming language are thoroughly explained as well. And that’s not all, the book also includes a useful appendix on the mikroC for dsPIC development environment, instructions on how to install it and how to use it to its full potential.

Title: Programming dsPIC (Digital Signal Controllers) in C
Authors: Zoran Milivojević, Djordje Šaponjić

LINK : http://www.mikroe.com/eng/products/view/266/programming-dspic-mcu-in-c/

May 10, 2012
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Altium Designer – High Speed Design Tutorial

The best high speed design tutorial for PCB layout in Altium Designer what I have found. It’s worth to have a look.

High-Speed Digital Board Design with Altium Designer by Istvan Nagy, Electronics Design Engineer, Blue Chip Technology. (download pdf here)

Picture: A page from the tutorial

The original file can be dowloaded here.

May 8, 2012
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Rotary Encoders

Rotary encoders are very versatile input devices for microcontroller projects. They are like potentiometers expect of digital nature and unlike analogue potentiometers they never wear down. Rotary encoders not only provide 360 degrees of rotational freedom they also allow digital positioning information to be gained without the use of analogue to digital converters (ADCs). When using rotational encoders in projects it’s possible to use the same encoder to represent a number of different input types, however this requires some form of feedback display to let the user know what information he is inputting and the ‘position’ of the encoder. The project is based around a 24 position rotary encoder, 16 LEDs arranged in a circle around the encoder, an A6276 16 LED serial driver IC and the PIC182550 microcontroller. A rotary encoder has 3 pins usually called A, B and C. The C pin (which is normally the centre pin) should be grounded and both A and B should be connected to the microcontroller with individual pull-up resistors on each input. In this project I used RB4 and RB5 on the PIC to connect the encoder; this has 2 advantages, firstly you can use the PORTB internal weak pull-up (which means you do not need external resistors) and also the PIC provides an ‘interrupt-on-change’ which can be used to monitor the encoder.

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