A metal detector is an electronic device that detects the presence of metal nearby. It works by using electromagnetic fields to sense metal objects—either on or below the ground or hidden inside other materials.
Components Used:
- 9012 Transistor *2
- 9018 Transistor *1
- 470 Ohm
- 2k Ohm
- 200k Ohm
- Red LED *1
- 222 Capacitor
- 104 Capacitor
- 100uf Capacitor
- Buzzer
- 3.7v Battery
- Switch
- Potentiometer
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Circuit Diagram:
9012 Transistor:
The 9012 transistor is a complementary PNP transistor to the 9014 NPN transistor. It’s used in similar low-power, general-purpose applications like switching and amplification in electronic circuits, especially in push-pull amplifier configurations when paired with the 9014.
🔍 9012 Transistor: Technical Specifications
| Parameter | Value |
|---|---|
| Type | PNP |
| Collector-Emitter Voltage (Vce) | -40V |
| Collector-Base Voltage (Vcb) | -50V |
| Emitter-Base Voltage (Veb) | -5V |
| Collector Current (Ic) | -800 mA |
| Power Dissipation (Ptot) | 625 mW |
| DC Current Gain (hFE) | 64 – 400 |
| Transition Frequency (fT) | 250 MHz |
| Package Type | TO-92 |
📦 Pin Configuration (TO-92 package)
Looking at the flat side of the TO-92 package with the pins facing down:
- Emitter (E) – Left
- Base (B) – Middle
- Collector (C) – Right
⚙️ Operating Regions (for PNP)
- Cut-off (OFF): Base voltage is more positive than emitter → no current flows.
- Active (Amplification): Base is slightly negative relative to emitter → collector current is proportional to base current.
- Saturation (ON/Switching): Base is much more negative than emitter → maximum current flows.
🛠️ Typical Uses
Hobby electronics.
Audio amplifiers (often with 9014)
Switching small loads
Complementary circuits (push-pull stages)
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