JOE GROELE
Project Outline The goal of this project was to build a plasma speaker that will amplify an electric guitar sound. Build an audio oscillator circuit using an ordinary speaker Test speaker performance compared to equations on data sheet Replace speaker with auto ignition coil to create a plasma arc Replace audio oscillator with an Audio Power Amplifier
Hypothesis I hypothesize that an Audio Power Amplifier will be capable of magnifying the output of an electric guitar through a plasma arc. The values of the measured frequency and duty cycle will match the equations on the data sheet for the oscillator circuit if built correctly.
Materials Solder Soldering iron Wire Wire strippers Wire Cutters Multimeter Oscilloscope Electronic tuner Perf board Auto spark ignition Connector terminal Power connector Guitar input jack Eight pin DIP socket 0.01 µf capacitor 0.1 µf capacitor 10 ohm resistor 330 ohm resistor 100 ohm resistor 1 K ohm resistor 10 K ohm potentiometer IRF510 MOSFET transistor P2N2222 transistor ICM7555 CMOS timer LM386 audio power amplifier
Constructing the Audio Oscillator Circuit Create the audio oscillator using the ICM7555 CMOS timer following the product data sheet Add amplifying transistors from example circuit Example circuit from: http://geocities.com/capecanaveral/lab/5322/fbt2.htm
Audio Oscillator Circuit Diagram 9 V POT1 10K 1K 330 S POT1 10K NMOS 1K 2 7 8 4 NPN IC M 7 5 5 5 10 3 100 6 1 2N2222 IRF510 C 0.1 or 0.01 GND
Testing the Audio Oscillator Circuit Connect speaker to the output Attach a 9 Volt battery Frequency and duty cycle are changed by adjusting the two potentiometers and the value of the capacitor Take measurements of frequency and duty cycle using an oscilloscope and an electronic tuner Compare to calculated values
Frequency and Duty Cycle Connect oscilloscope and take measurements, T 1 and T 2 Use ohm meter to measure R A and R B Adjust potentiometers and repeat measurements T1 T2 Measured: F = 1 T 2 D = T T 1 2 Calculated: 1.38 F = ( RA + 2RB ) C D = R R A A + R + 2R B B
Creating a Plasma Speaker Replace speaker with auto ignition coil Connect wires from the primary coil to the circuit board Attach wires to the secondary high voltage coil Adjust spacing between wires to create a small gap - 2 to 5mm worked best When the circuit is energized, the air between the electrodes is ionized and becomes a plasma A new spark is created with every oscillation of the circuit Your ear hears this as a musical tone The frequency or note of the tone can be adjusted using the potentiometers
Creating the Plasma Powered Guitar Amp A second copy of the circuit was constructed, replacing the oscillator chip with a low voltage audio power amplifier The gain of the amplifier was increased to 200, which gives a square shaped wave form The spark also produces a sound, but now the frequency corresponds to the note being played on the guitar C6 = 1046.5 Hz C5 = 523.25 Hz
Audio Oscillator Diagram With Coil 9 V POT1 10K R A 1K 330 T Auto Ignition Coil POT1 10K NMOS R B 1K 2 7 8 4 IC M 7 5 5 5 6 1 3 100 NPN 2N2222 10 IRF510 C 0.1 or 0.01 GND
The FaceMelter3000 1 2 V C 10, 450V.. GND G? 330 T Auto Ignition Coil C PHONEJ tip 10uF NMOS J? 3 + 1 6 8 5 LM386 NPN 10 2-100 2N2222 IRF510 4 7 GND
Data and Calcula+ons RA,k ohms RB, k ohms C, nf T1, div T2, div Scale, seconds/ div Calculated Frequency, Hz Calculated Duty Cycle, % Measured Frequency, Hz Measured Duty Cycle, % Note 1 11.52 11.19 116.7 3.3 5.1 0.0005 348.8 66.99% 392.2 64.71% 2 8.41 11.19 116.7 2.9 4.7 0.0005 384.1 63.66% 425.5 61.70% 3 4.12 11.19 116.7 2.2 4 0.0005 446.2 57.77% 500.0 55.00% 4 1.003 11.19 116.7 4.3 9 0.0002 505.7 52.14% 555.6 47.78% 5 11.52 7.62 116.7 7 10 0.0002 441.9 71.52% 500.0 70.00% 6 7.86 7.62 116.7 5.5 8.6 0.0002 511.9 67.01% 581.4 63.95% 7 4.88 7.62 116.7 4.5 7.6 0.0002 587.7 62.13% 657.9 59.21% 8 1.003 7.62 116.7 3 6.1 0.0002 728.0 53.09% 819.7 49.18% 9 11.52 4.39 116.7 5.8 7.5 0.0002 582.5 78.37% 666.7 77.33% 10 8.35 4.39 116.7 4.5 6.2 0.0002 690.3 74.37% 806.5 72.58% 11 4.4 4.39 116.7 6.2 9.8 0.0001 897.2 66.69% 1020.4 63.27% 12 1.003 4.39 116.7 3.9 7.3 0.0001 1208.7 55.13% 1369.9 53.42% 13 11.52 1.003 116.7 9 9.8 0.0001 874.3 92.58% 1020.4 91.84% 14 7.44 1.003 116.7 6 6.9 0.0001 1251.9 89.38% 1449.3 86.96% 15 4.19 1.003 116.7 7.2 8.9 0.00005 1908.5 83.81% 2247.2 80.90% 16 1.003 1.003 116.7 2.9 4.4 0.00005 3929.9 66.67% 4545.5 65.91% 1 11.51 11.18 13.16 4.4 6.9 0.00005 3096.1 66.99% 2898.6 63.77% 2 8.87 11.18 13.16 3.9 6.1 0.00005 3357.8 64.20% 3278.7 63.93% 3 4.48 11.18 13.16 3 5.3 0.00005 3907.0 58.35% 3773.6 56.60% 4 1.003 11.18 13.16 2.2 4.7 0.00005 4488.4 52.15% 4255.3 46.81% 5 11.52 7.58 13.16 3.7 5.2 0.00005 3930.4 71.59% 3846.2 71.15% 6 7.88 7.58 13.16 3 4.7 0.00005 4551.4 67.10% 4255.3 63.83% 7 5.08 7.58 13.16 6 10 0.00002 5181.0 62.55% 5000.0 60.00% 8 1.004 7.58 13.16 4 8.1 0.00002 6487.5 53.11% 6172.8 49.38% 9 11.51 3.79 13.16 7.2 9.2 0.00002 5493.1 80.15% 5434.8 78.26% 10 7.87 3.79 13.16 5.6 7.5 0.00002 6787.3 75.47% 6666.7 74.67% 11 4.55 3.79 13.16 4 6 0.00002 8644.9 68.76% 8333.3 66.67% 12 1.003 3.79 13.16 2.2 4.3 0.00002 12217.5 55.84% 11627.9 51.16% 13 11.51 1.004 13.16 6 6.7 0.00002 7757.3 92.57% 7462.7 89.55% 14 8.08 1.004 13.16 8.8 9.8 0.00001 10394.8 90.05% 10204.1 89.80% 15 4.25 1.004 13.16 5 6.1 0.00001 16756.7 83.96% 16393.4 81.97% 16 1.003 1.004 13.16 4 6.1 0.000005 34826.7 66.66% 32786.9 65.57% 17 11.49 10.53 116.7 3.7 5.9 0.0005 363.3 67.65% 339.0 62.71% F4 18 6.42 6.14 116.7 5.2 8.3 0.0002 632.4 67.17% 602.4 62.65% D#5 19 3.28 2.16 116.7 4.3 6.7 0.0001 1555.9 71.58% 1492.5 64.18% G6 20 2.557 2.047 116.7 3.9 5.9 0.0001 1778.0 69.22% 1694.9 66.10% A6 21 1.113 1.014 116.7 3.4 5.5 0.00005 3764.8 67.72% 3636.4 61.82% A#7 22 9.08 9.68 950.4 3.1 5.2 0.005 51.1 65.96% 38.5 59.62% D#1 23 7.87 7.86 950.4 2.7 4.3 0.005 61.6 66.68% 46.5 62.79% F#1 24 1.465 3.96 950.4 4.3 8.2 0.001 154.7 57.81% 122.0 52.44% B2 25 1.807 2.87 950.4 3.8 6.7 0.001 192.4 61.97% 149.3 56.72% D#3
40000.0 Comparison of Measured and Calculated Frequency 35000.0 30000.0 Measured Frequency, Hz 25000.0 20000.0 15000.0 10000.0 5000.0 0.0 0.0 5000.0 10000.0 15000.0 20000.0 25000.0 30000.0 35000.0 40000.0 Calculated Frequency, Hz
4000.0 3500.0 Comparison of Measured and Calculated Frequency A#7 3000.0 Measured Frequency, Hz 2500.0 2000.0 1500.0 1000.0 G6 A6 Scale notes' frequencies measured using an electric tuner. 500.0 D#5 F4 D#3 D#1 B2 F#1 0.0 0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0 3500.0 4000.0 Calculated Frequency, Hz
Comparison of Measured and Calculated Duty Cycles 90.00% 80.00% Measured Duty Cycle, % 70.00% 60.00% 50.00% 40.00% 50.00% 55.00% 60.00% 65.00% 70.00% 75.00% 80.00% 85.00% 90.00% 95.00% Calculated Duty Cycle, %
Conclusions Measured values of frequency and duty cycle were only two significant figures, resulting in less accuracy The electronic tuner was more accurate than the oscilloscope because the tuner, like an ear, can hear smaller differences in frequency verified by comparing the pitch to a piano The plasma guitar amplifier produced a satisfactory sound, but the volume and sustain could be dramatically improved