Schmitt Trigger Synthesizer

Published

Introduction: Schmitt Trigger Synthesizer

A Simple Synthesizer using a Schmitt trigger

For this circuit, you may need to connect the audio jack to a guitar amp. A regular stereo out may not have enough gain to hear the signal.


A Schmitt trigger is a type of threshold circuit with positive feedback. The circuit is named "trigger" because the output retains its value until the input changes sufficiently to trigger a change. A Schmitt trigger is a bistable multivibrator; in its inverting configuration it can be used as an oscillator. The integrated circuit chip we are using is called a hex Schmitt trigger because it has six inverters on one chip. For this exercise, you can use 74C14 or CD40106, they are both Hex Schmitt Triggers.

Single inverter

  • pin 14 goes to voltage source
  • pin 7 goes to ground
  • R1 = 10k (resistor between pin 1 and pin 2)
  • C1 = .1uF (capacitor between pin 1 and ground)
  • The hot tip of the audio jack connects to pin 2, which is the OUTput signal
  • The sleeve of the audio jack connects to ground

Step 1: ​Set Up One Oscillator, and Connect It So We Can Hear It

Step 2: Replace the Resistor With a Photoresistor

Step 3: Replace the Resistor With a Potentiometer

Step 4: Multimeter: Measure the Resistance of the Photoresistor and Potentiometer

Write down the range of resistance for your potentiometer and photoresistor.

Two inverters

  • pin 14 goes to voltage source
  • pin 7 goes to ground
  • R1 = 10k (resistor between pin 1 and pin 2)
  • R2 = 10k (resistor between pin 3 and pin 4)
  • C1 = .1uF (capacitor between pin 1 and ground)
  • C2 = .1uF (capacitor between pin 3 and ground)
  • R3 = 10k (resistor between pin 2 and OUT)
  • R4 = 10k (resistor between pin 4 and OUT)
  • The hot tip of the audio jack connects to OUT
  • The sleeve of the audio jack connects to ground

Step 5: ​Use Two Inverters

To connect multple inverters to the same audio output, send each signal through a 10k resistor which all terminate at the hot tip of the audio jack. To play with the signal, could substitute R1 and/or R2 for variable resistors like a potentiometer or photoresistor.

Step 6: Use Three Inverters

Step 7: Use Three Inverters

This time use a 10k resistor for inverter #1, a potentiometer for inverter #2, and a photoresistor for inverter #3.

Step 8:

Share

    Recommendations

    • Make it Move Contest

      Make it Move Contest
    • Clocks Contest

      Clocks Contest
    • Oil Contest

      Oil Contest
    user

    We have a be nice policy.
    Please be positive and constructive.

    Tips

    Questions

    Comments