Prometheus Style TV Remote

I want to use a musical instrument to turn on my TV like the Engineers in the movie Prometheus started their control system

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There is a great scene in the movie Prometheus where David starts the Engineer's control system using a pipe by playing a specific sequence of notes. A TV is a sad excuse for a spaceship, but it does take me places and show me things. The goal for this project is to set up a system that uses a microphone to collect sounds, an arduino to process the signal, and an IR LED to send commands to the TV. Hopefully we can learn about high and low pass filtering, getting an AC signal into the arduino, various ways of determining tones (zero crossings, auto-correlation, etc), and sending IR signals.

The main building blocks of this device are:

An analog section that correctly biases a microphone, uses a bandpass filter to limit the range of frequencies, amplifies the signal to almost 5V P2P, then adds a +2.5V offset to get the range of the signal 0-5V. If possible, it would be nice if we could use a single sided power supply to power the op amp rather than using two supplies.

An Arduino for its A/D convertor, data processing, and digital outputs. Ideally we will try a few techniques to detect tones from the instrument. The one technique I think will be the winner is the Discrete Fourier Transform, but it will be good to check FFT (if it fits onto the Arduino I don't know), counting zero crossings, and autocorrelation as well.

Finally, an IR LED section to send the correct signals to the TV. Naturally, you can't send a signal without knowing the signal first, so we will also need to read signals from the remote controller that turns the TV on now.

The hope is that after it all works, the basic design can be adjusted for other tone based projects. One idea is a Simon type game with tones rather than colored lights. Another is a game where Oompaloompas are controlled through some course with tones.

  • Ran out of time short term

    Mirrorsails04/26/2014 at 12:31 0 comments

    My job and schedule have gotten in the way of finishing this project before the end of April.  Funny thing is after the first week in May I'll have lots of spare time.  It will get finished, but I don't want to rush the experience just for the contest.

    I'm hoping to find a piece of light gray slate tile of the correct size and draw the cave painting of the man pointing at the stars.  The painting will be done in charcoal pencil.  Then somehow I need to drill holes through and put LEDs in as the stars.  For each correct note played on the recorder (I had no space pipe laying around) another LED would light.

    I also need to bight the bullet and order some parts.  I got hung up on exactly which op amp would be ideal, rather than which one would work.  I need a dual op amp for the two stage active filter, and I'm thinking of the humble 741 for the stability of the V/2 signal.

    Thanks to everyone for their support so far.

  • Single Supply Op Amps

    Mirrorsails03/22/2014 at 22:01 0 comments

    I had one of the learning experiences last night where you set out to learn one piece of the puzzle, and the answers to that one piece cascade into solving other problems as well. It started with not knowing how to bias an op amp with a single sided supply, and ended up showing me that you can create bandpass filters on op amps with single sided supplies that have output signals at V/2. So I can get everything in one shot!

    While searching I came across an application note from Texas Instruments, A Single-Supply Op-Amp Circuit Collection. Of all the pages and app notes I read, that one was the best I found at not only explaining single sided supplies, but showing how they were applied. On page 17 is a multiple feedback configuration of a bandpass filter.  I seem to have forgotten that it's possible to use the feedback from the op amp to filter.  Originally I was planning on a low pass filter followed by a high pass filter.

    Another cool thing I came across was Erik Cheever's Single Supply Op Amp Design. I know it's been a long time since I was in school, and as an ME I may not have been as interested in electronics back then, but I never quite got why I might want to use an inverting op amp rather than a non inverting one. This page explained that in an inverting configuration, there is no current going to ground. So it makes a better choice when you are using a single sided source because that current can wind up changing your reference voltage. It was like a light-bulb went off.

    Finally, I can across two online calculators that let you design filters. The first was WEBENCH from TI and the other was Analog Filter Wizard from Analog Devices. They show a lot more depth to the choices between configurations. Who knew there was roll off and ripple to worry about? It also looks like I might need more than one op amp, although I want to stick with one if I can.

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