Music Synthesis using the 555 Timer IC Chip

Chris Whiting & Keddy Malcolm

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555 Timer Pin Layout 555 Timer Configuration 555 Timer – Other Applications Malcolm Results Whiting Results Conclusion Sources

2

TRIG

OUT rises, and interval starts, when this input falls below 1/3 VCC.

6

THR

The interval ends when the voltage at THR is greater than at 2/3 Vcc.

4

RESET

A timing interval may be reset by driving this input to GND, but the timing does not begin again until RESET rises above approximately 0.7 volts.

5

CTRL

"Control" access to the internal voltage divider (by default, 2/3 VCC).

7

DIS

Open collector output; may discharge a capacitor between intervals. In phase with output.

3

OUT

This output is driven to approximately 1.7V below +Vcc or GND.

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Square wave output, how? Capacitor Charge Time: T1 = 0.693(R1+R2)C1 Capacitor Discharge Time: T2 = 0.693(R2)C1 The output frequency is determined by the following equation:

Simple astable configuration

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Duty Cycle of waveform – Pulse Width/Period The Duty cycle is determined by the following equation:

Duty Cycle Relationship to output frequency Large R2 wrt R1 Control capacitor reduces noise

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Two modes of operation:  Monostable Mode – Output Single Pulse  Astable Mode – Output Continuous Pulses  Bistable Mode – Output acts as Basic Flip-Flop

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Linear Ramp Pulse Width Modulator Frequency Divider

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Linear Ramp

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Pulse Width Modulator

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Frequency Divider

Switch Placement

Week One: • Change resistors to get frequencies correct • Mistakes in wiring

Week Two: • Problems with wiring • Balance between volume and waveform output • Component Precision

Theory 261.625 293.664 329.627 349.228 391.995 440 493.883 523.251

Actual High Time Low Time Duty Cycle RB 260.7 1.86ms 1.76ms 51.38% 26.7k 290.7 1.64ms 1.66ms 49.70% 23.9k 335 1.42ms 1.42ms 50.00% 20.49k 351.2 1.41ms 1.41ms 50.00% 19.6k 390.6 1.27ms 1.28ms 49.80% 17.6k 431 1.14ms 1.12ms 50.44% 15.9k 494 1.02ms 1.01ms 50.25% 13.8k 530.8 968us 948us 50.52% 12.86k

RA .995k

• Rise time: 1.86 ms • Fall time: 1.76 ms • Duty Cycle: 51.38%

• High Time: 1.64ms • Low Time : 1.66ms • Duty Cycle: 49.7%

• High Time: 1.42ms • Low Time: 1.42ms • Duty Cycle: 50%

• High Time: 1.41ms • Low Time: 1.41ms • Duty Cycle: 50%

• High Time: 1.27ms • Low Time: 1.28ms • Duty Cycle: 49.80%

• High Time 1.14ms • Low Time 1.12ms • Duty Cycle: 50.80%

• High Time: 1.02ms • Low Time: 1.01ms • Duty Cycle: 50.44%

• High Time: 968us • Low time: 948 us • Duty Cycle: 50.25%

Theory Calculated frequency 261.625 264Hz 270.54Hz 293.664 295Hz 303.55 Hz 329.627 343Hz 354.93 Hz 349.228 358Hz 372.66 Hz 391.995 397Hz 416.67 Hz 440 439Hz 462.01 Hz 493.883 503Hz 528.73 Hz 523.251 539Hz 580.81 Hz

current 16.7mA 17.3mA 17.4mA 17.5mA 17.6mA 17.9mA 18mA 18.2mA

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Frequencies and duty cycle very accurate in first stage Frequencies loose accuracy in the second stage Excellent sine wave poor volume quality

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Used potentiometers in the lab to more accurately obtain desired output frequencies

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R2 value determines output frequency. Duty Cycle unaffected because R2 >> R1 Various switches with potentiometers are used to act as selectors for the output frequency by turning each switch on or off.

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555 Timer Square Wave Output Sine Wave A square wave is the sum of multiple sine waves at odd multiples of the square wave’s frequency (odd order harmonics)

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Extract the fundamental frequency of the square wave by filtering the higher order sine waves. Low-pass filter with 600 Hz cutoff frequency and an inverting op-amp connected in series.

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Theoretical & Experimental results for 555 timer circuit square wave output

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Different resistances attributed to:  Potentiometers, inaccurate capacitors, 555 timer

18.52% Difference?!

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Theoretical & Experimental results for 555 timer and filter combination sine wave output

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Different resistances attributed to:  Potentiometers, inaccurate capacitors, 555 timer

20.08% Difference?!

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Square wave to Sine Wave conversion Duty Cycle = 50.0% 0.2% error on average

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Square wave to Sine Wave conversion Duty Cycle = 50.0% 0.2% error on average

524.091Hz

523.063Hz

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555 Timer Pin Layout 555 Timer Configuration 555 Timer – Other Applications Malcolm Results Whiting Results

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http://blog.makezine.com/2008/01/29/howto-guitar-hero-autowh/ http://www.ecelab.com/circuit-astable555.htm http://www.cc.gatech.edu/classes/AY2011/cs 3651_spring/docs/LM555.pdf http://home.cogeco.ca/~rpaisley4/LM555.ht ml