Gamma radiation is highly dangerous for the human body, so detecting this type of radioactive rays is important in hospitals, home near to the radioactive power plants. You can also use this device to find out any radioactive substance is present near your home. Here I am sharing a cost effective circuit with a buzzer to detect the radiation. This radiation detector is working based on a BPW34 photo diode and LM311 IC. The circuit diagram, connection and its working is explained below.
BPW34 Photodiode
This BPW34 Photodiode will detect the gamma rays. It is build with flat glass epoxy sense for pointing the light and radiations for efficient measuring. This photo diode is made with large silicon depletion region, this region is enough to capture the sensitive gamma radiations. When the gamma ray detected the diode. producing a small voltage inside the diode. This voltage is amplified by the radiation detector circuit using LM311 IC.
Gamma Radiation Detector Circuit Diagram
Components Required
| Component | Value/Part Number | Quantity |
|---|---|---|
| PV1, PV2, PV3 | BPW34 | 3 |
| R1, R3 | 220kΩ | 2 |
| R2, R11 | 2M2 (2.2MΩ) | 2 |
| R4 | 4.7kΩ | 1 |
| R5 | 1kΩ | 1 |
| R6 | 10Ω | 1 |
| R7, R9, R12 | 33kΩ | 3 |
| R8, R10 | 100kΩ | 2 |
| R13 | 1kΩ | 1 |
| C1, C4 | 100nF | 2 |
| C2, C6 | 10μF | 2 |
| C3, C5 | 100nF (estimated) | 2 |
| Q1, Q2 | BC549C | 2 |
| Q3 | BC547C | 1 |
| U1 | LM311N | 1 |
| LS1 | Buzzer | 1 |
| Power | 9V Battery + Connector | 1 |
Connection and Working of Circuit
This radiation detector circuit requires a 9V battery as a power source. The capacitors C5 and C6 is used to filter the input DC voltage. The main part of the circuit is BPW34 photo diode. The three BPW34 diodes are used to detect the gamma radiation.
When any gamma radiation is falls on the surface of the diode, it will produce a small electrical charge within this diode. This generated electrical charge is very small and weak. The weak charge is then amplified by the two transistors Q1 and Q2. The amplified signal is then fed to the input pin of a LM311 comparator IC.
The IC will compare the incoming signal with a fixed reference voltage established by using the resistors of R9 and R10. When the radiation signal is greater than the reference voltage the comparator output becomes high.
This output voltage will activate another transistor Q3 that will activate the connected buzzer. The buzzer will beep if any gamma radiation is detected.
