For my final project, I built a synthesizer. There are 5 arcade buttons, and each button plays a different pitch. There is a droning tone, and the pitch can be changed using a knob. Vibrato is a pulsating change of pitch. This effect is created using an LED and a photocell, and the speed, how fast the pitch changes, can be changed using a knob. Tremolo is a pulsating change of volume. This effect is created using a Voltage Controlled Amplifier and Voltage Control from an Oscillator. Its speed can also be changed using a knob.
Output Frequency = (1/(4*Rt*C))(R2/R1)
This is the main OpAmp Oscillator that generates the sound. Each button completes the circuit with different sets of resistors in series; thus producing different pitch. A photocell is added after the resistors and buttons, and it is enclosed in electrical tape with a pulsating LED; this will create the vibrato effect. A STDP switch is added to bypass the photocell and turn off vibrato. The output of this oscillator then goes into the summing amplifier.
- R1 = 1kΩ
- R2 = 100kΩ
- C = 1uF
- Rt = 47k + 22k + 3.3k = 72.3kΩ
- f = (1/(4*72.3kΩ*1uF))(100kΩ/1kΩ) = 345.78 Hz
- Rt = 47k + 10k + 3.3k = 60.3kΩ
- f = (1/(4*60.3kΩ*1uF))(100kΩ/1kΩ) = 414.59 Hz
- Rt = 47k + 10k = 57kΩ
- f = (1/(4*57kΩ*1uF))(100kΩ/1kΩ) = 438.60 Hz
- Rt = 22k + 22k + 10k = 54kΩ
- f = (1/(4*54kΩ*1uF))(100kΩ/1kΩ) = 462.96 Hz
- Rt = 22k + 22k + 1k = 45kΩ
- f = (1/(4*45kΩ*1uF))(100kΩ/1kΩ) = 555.56 Hz
This is the main OpAmp Oscillator that generates the sound. Each button completes the circuit with different sets of resistors in series; thus producing different pitch. A photocell is added after the resistors and buttons, and it is enclosed in electrical tape with a pulsating LED; this will create the vibrato effect. A STDP switch is added to bypass the photocell and turn off vibrato. The output of this oscillator then goes into the summing amplifier.
Output Frequency = (1/(4*Rt*C))(R2/R1)
Manimum Frequency = (1/(4*10kΩ*100uF))(4.7kΩ/3.3kΩ) = 0.356 Hz
This Oscillator is for vibrato. It makes the LED, which is enclosed in electrical tape with a photocell, pulse. Thus changing the pitch of the sound generated by the main OpAmp Oscillator. The potentiometer changes the frequency of the wave, which changes the speed of LED pulse.
- R1 = 3.3kΩ
- R2 = 4.7kΩ
- C = 100uF
- Rtmax = 10kΩ
- Rtmin = 10Ω
Manimum Frequency = (1/(4*10kΩ*100uF))(4.7kΩ/3.3kΩ) = 0.356 Hz
This Oscillator is for vibrato. It makes the LED, which is enclosed in electrical tape with a photocell, pulse. Thus changing the pitch of the sound generated by the main OpAmp Oscillator. The potentiometer changes the frequency of the wave, which changes the speed of LED pulse.
Output Frequency = 1.44/((R1 + (2*R2))*C)
Minimum Frequency = 1.44/((50kΩ + (2*1kΩ))*0.5uF) = 55.35 Hz
This is a simple 555 timer oscillator that will generated a droning tone. The output frequency can be changed using the potentiometer. The output of the oscillator goes into the summing amplifier
- R1max = 50kΩ
- R1min = 100Ω
- R2 = 1kΩ
- C =0.5uF
Minimum Frequency = 1.44/((50kΩ + (2*1kΩ))*0.5uF) = 55.35 Hz
This is a simple 555 timer oscillator that will generated a droning tone. The output frequency can be changed using the potentiometer. The output of the oscillator goes into the summing amplifier
Vout = (Rf/R1)(Vin1 + Vin2)
Gain = Rf/R1
Maximum Gain = 100kΩ/41141 Hz = 2.43
Minimum Gain = 100Ω/41141 Hz = 0.002
This is the summing amplifier. It takes outputs from both the main OpAmp Oscillator and 555 Timer Oscillator, and amplifies it. The potentiometer is used to turn up/down the volume. The output of the amplifier goes into VCA.
Gain = Rf/R1
- Rfmax = 100kΩ
- Rfmin = 100Ω
- R1 = (330kΩ * 47kΩ)/(330kΩ + 47kΩ) = 41141 Hz
Maximum Gain = 100kΩ/41141 Hz = 2.43
Minimum Gain = 100Ω/41141 Hz = 0.002
This is the summing amplifier. It takes outputs from both the main OpAmp Oscillator and 555 Timer Oscillator, and amplifies it. The potentiometer is used to turn up/down the volume. The output of the amplifier goes into VCA.
Output Frequency = (1/(4*Rt*C))(R2/R1)
Minimum Frequency = (1/(4*5kΩ*100uF))(4.7kΩ/3.3kΩ) = 0.712 Hz
This is the last component in the circuit. It is a VCA that will create the tremolo effect. An OpAmp Oscillator generates square wave and triangle wave which will go into the VCA as a voltage control. A switch is added to swtich between square wave and triangle wave. A potentiometer changes the frequency of the waves; thus changing the speed of tremolo.
- R1 = 3.3kΩ
- R2 = 4.7kΩ
- C = 100uF
- Rtmax = 5kΩ
- Rtmin = 10Ω
Minimum Frequency = (1/(4*5kΩ*100uF))(4.7kΩ/3.3kΩ) = 0.712 Hz
This is the last component in the circuit. It is a VCA that will create the tremolo effect. An OpAmp Oscillator generates square wave and triangle wave which will go into the VCA as a voltage control. A switch is added to swtich between square wave and triangle wave. A potentiometer changes the frequency of the waves; thus changing the speed of tremolo.