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FABLAB Delhi

FABLAB Delhi. Dhananjay V. Gadre. List of Projects. Flickering Candle Electronic Batteryless dice Led Pen Electronic Birthday Blowout Candles Audio Spectrum Analyzer Twilight Switch. Flickering LED candle. Flickering Candle. An LED can be used to mimic candle light.

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FABLAB Delhi

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  1. FABLAB Delhi Dhananjay V. Gadre

  2. List of Projects • Flickering Candle • Electronic Batteryless dice • Led Pen • Electronic Birthday Blowout Candles • Audio Spectrum Analyzer • Twilight Switch

  3. Flickering LED candle

  4. Flickering Candle • An LED can be used to mimic candle light. • The trick to mimicking a candle lies in recreating the way a candle flickers. • The candle flame sways randomly (or so it seems) and sometimes the intensity of the flame seems to vary with air currents. • While using an LED to behave like a candle, it may not be possible to make the ‘flame’ sway, but what can certainly be achieved is the random variation of intensity

  5. Concept – Theory of Operation • For randomization, a particular type of pseudorandom generators known as linear feedback shift registers (LFSRs) have been used.

  6. Concept – Theory of Operation (contd…) • An LFSR is a shift register the input to which is the exclusive-or (XOR) of some of the bits of the register itself. • The bit positions that are used for the XOR operation to yield the input bit are called taps.

  7. Implementation • The pseudo-random number generator and the intensity control of the LED have been implemented using AVR ATiny13 microcontroller. • The circuit has been split into two boards: the controller board and the LED holder board. • The LED holder board is placed on top of the controller board so as to minimize the footprint of the circuit board. This way it occupies less space and can easily be packaged in a tube to give a feel of a candle.

  8. The Project Hardware

  9. Electronic Batteryless dice

  10. Electronic Batteryless dice • There has been a lot of interest in muscle powered electronic devices. • The muscle powered voltage generator is based on Faraday's law, consisting of a tube with cylindrical magnets. It is also called Faraday generator. • Instead of a traditional dice, it is nice and cool to use an electronic dice that is powered from faraday generator. • Moreover, since the faraday generator produces power only when it is shaken, it mimics the shake of real dice.

  11. Concept – Theory of Operation • Faraday Generator produces AC output voltage. So, it is rectified and then filtered by a capacitor. • The capacitor voltage is then regulated and used to power the electronic circuit required for the dice. • The dice is mimicked by seven 3mm LEDs arranged in the traditional pattern of dots on the dice.

  12. Concept – Theory of Operation (contd…) • The pulsed output from the generator is also fed to the microcontroller to determine whether the tube is being shaken or not.

  13. Implementation

  14. The Project Hardware

  15. LED pen

  16. LED pen • You might have seen advertisements by battery manufacturers in which images are drawn in the air and captured by a long exposure camera • Now imagine, instead of a flashlight, you have a multicolor LED pen with which to draw these pictures and image? • This is exactly what this project achieves. • Such images and pictures are called light doodles.

  17. LED doodles

  18. Concept – Theory of Operation • The LED used is a RGB LED. • By the use of PWM on each color component, It can be used to generate multiple colors. • Sixteen colors have been selected in this project. • There is an on-off switch to change the state of the LED and a potentiometer to change the color of the LED. • The output of the potentiometer is fed to the ADC input channel of the microcontroller.

  19. Implementation

  20. The Project Hardware

  21. Electronic Birthday Blowout Candles

  22. Electronic Birthday Blowout Candles • The Electronic Birthday Blowout Candles emulate the conventional candles (arranged on a birthday cake) • LEDs have been used as small candles. • They flicker randomly to give the appearance of real candles. • Moreover, they also go off in a random fashion when someone blows air on them. • When all the LEDs have been extinguished, a tone of “Happy Birthday to you” is played.

  23. Concept – Theory of Operation • 20 LEDs have been connected in a multiplexed fashion. • Their intensity is varied to give a flickering effect. • The sensor part consists of a thermistor in series with a resistor. • The thermistor is also in thermal contact with a high power resistor(1/2W) which raises its temperature above room temperature.

  24. Concept – Theory of Operation (contd…) • When user blows on it, the thermistor gets cooled which increases its resistance. • This is detected by the microcontroller and random number of LEDs are extinguished. • The controller used is ATmega8.

  25. The Project Hardware

  26. Audio Spectrum Analyzer

  27. Audio Spectrum Analyzer • Spectrum Analyzer made is based on 5 FIR filters implemented in ATmega88 microcontoller. • The audio range from 200 Hz – 9600 Hz has been broken down into 5 subbands. 200 – 600 Hz 600 – 1200 Hz 1200 – 2400 Hz 2400 – 4800 Hz 4800 – 9600 Hz

  28. Twilight Switch

  29. What is the Twilight Switch? • An AVR implementation of a fully autonomous sensor-less switch for outdoor artificial lighting that operates at twilight time • Project addresses the twin concerns of road safety and energy conservation • After one-time configuration, automatically calculates and operates a relay/switch at twilight times.

  30. Concept – Theory of Operation • The current locations geographical coordinates and local time are required. These are configured one-time. • A clock is maintained with the AVR’s 16 bit timer and crystal oscillator. • Twilight time is calculated with precise formulae – a modified form of the Sunrise Equation. • A switch is operated to turn on lighting at end of twilight time and turn it off at beginning of twilight time.

  31. Implementation • The Twilight switch code, consisting of precise twilight time calculations, UART configuration interface and onboard timekeeping, fits on an Atmega8 • A configuration and display terminal (via UART), also on Atmega8, with LCD and keypad interface, eliminates the need of a PC for configuration. • A working prototype is in operation at CEDT, New Delhi

  32. The Project Hardware The Configuration Terminal Backup Battery Twilight Switch Configuration Keypad

  33. Review of Salient Features • Calculations happen once a day; ‘tick’ is recorded every 8 seconds and switch is operated twice a day. The kit stays in power-save mode rest of the time. • The formulae are accurate to within  2 minutes for any geographical location and time of the year. Maximum error at poles. • Crystal used for timekeeping gives a drift of 1 sec/day because of temperature effects. We are investigating use of a temperature-controlled RTC that gives a max error of 2min/year. • A transistor driver/relay may be used to operate a lamp drawing power from a higher voltage source.

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