Simple Ultrasonic Wave Generator

Ultrasonic sound wave can be generated using electronic circuit. This simple electronic circuit can generate an ultrasonic wave with frequency range of 12 to 50 kHz. Its very easy and quick to make this circuit. This circuit uses NE555 IC timer to drive a speaker. SPKR1 can be piezzo tweeter, etc. If you use a moving coil tweeter, then it is recommended to add a decoupling capacitor around 1uF-2.2uF/16V to block the DC voltage. For adding a circuit safety, you’d better insert a 1k resistor between R2 and the positive supply line, since the pin 7 of 555I C will be internally shorted to ground at the discharging cycle. It’s not clearly shown in the schematic diagram, but C1 should be a small 1.8 nF non-polar capacitor. Here is the schematic diagram of this circuit: