Vibration Bug

This article shows a vibration bug. The vibration speaker is activated when the bug is placed in water. The device also works as a touch switch.

I learned from those articles:

https://www.instructables.com/Transistor-Vibrator-Kit/

https://www.instructables.com/MOSFET-Touch-Lamp/

Supplies

Components: general purpose bipolar junction (BJT) NPN/PNP transistors - 5, 1 kohm low power resistor - 1, 10 kohm low power resistor - 1, 100 ohm (or 10 ohms) high power resistor - 1, matrix board, vibration speaker - 3.

Tools: wire stripper.

Optional components: solder, Schottky/silicon diode (do not use low power diodes).

Optional tools: soldering iron, multimeter.

Step 1: Design the Circuit

The vibration speaker is modeled as 500 ohms. Various speakers have different resistor values.

Calculate the maximum vibration speaker current:

Ivbs = (Vs - Vsat) / (Rspeaker + Ro)

= (9 V - 0.2 V) / (500 ohms + 100 ohms) = 8.8 V / 600 ohms

= 14.66666666 mA

Keep in mind that you might need to use a 10-ohm Ro resistor value instead of 100 ohms to increase the current value.

Step 2: Simulations

I used the old PSpice simulation software, student edition version 9.1.

The maximum vibration speaker current is almost similar to the predicted value.

Step 3: Make the Circuit

I created the circuit on a piece of cardboard. Using a matrix board is a better method due to risk of water damaging your cardboard circuit.

Step 4: Attach to Board

I used blu tack to attach the 9V battery, circuit, and leads to the wooden board.

Step 5: Testing

Testing shows my sculpture is working.