Description:Here we have used LDR module where its positive terminal is connected to the DC +5V and the negative terminal is connected to the ground. The digital out pin of the LDR module is connected to the buzzer’s negative terminal, and the positive terminal of the buzzer is connected to the +5V DC. Now the positive terminal of the red LED is connected to +5V DC supply and the negative to the ground terminal. Here we have denoted the positive terminal by red colour and negative terminal by black colour. This device is powered by an external 12V DC adapter which is later sent to the DC step down module to regulate the voltage to + 5V. This device can also be powered by using a battery. In this set-up, the LDR module is attached to one side of the blood bag and the red LED to the opposite side of the LDR module so that whenever the blood bag gets empty, the light will travel towards the LDR module through the transparent bag and will trigger the buzzer and it will beep accordingly. , Claims:We Claim:
1. This system does not generate radiation

2. This system does not create radio interferences

3. This system is an external system

4. This system does not create health hazards

5. This is a waterproof device

6. Increasing of the limiting voltage may damage the device

7. The device works on a basic principle of LDR trigger

8. This device is compact

9. This device can also be run using a battery

10. This device is very safe to use which does not require any internal activity