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USB Light. Home Utility Circuit 30

Harvest energy from the USB port of your Laptop or PC to light an LED lamp. It is useful as an Emergency lamp in the event of a power failure or it can help you to use the Key pad in night without disturbing the sleep of others. It is too simple and easy to make it. The USB.2 .0 port available in all laptops and PC gives 5 Volt DC and 200-300 milli ampere current. It is enough to light a High power 1  watt LED. Just plug the light in the USB port and enjoy its light. Cool! it is good enough to read a book also. In the market its costs Rs. 300 and you can make it for just Rs.10.
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Power Failure Alarm. Home Utility Circuit 29

A2This circuit generates an alarm when the Mains power fails. It can be used as a Lift Alert so that the technician can immediately attend the stopped Lift. It is also helpful to know the power failure in labs where many instruments are switched on continuously.
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Car Light. Home Utility Circuit 28

8AThis is a simple 10 Watts LED light you can easily make. It will help you to check the engine, battery terminals or other parts of Car during night. It will act as an efficient high intensity Torch light. It is also useful to check the inverter and its battery usually placed in low light areas. By hooking the clips in the battery, the light will turn on. If you fix a Magnet with it, you can stick the lamp to the vehicle’s body so that your hands will be free to do work. Let us make it. Its cost is Rs.50 only.
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Home Made Power Supply. Home Utility Circuit 27

2AThis Homemade Power supply is useful for the Electronics hobbyists and service persons to test and troubleshoot the circuits. It gives six stage well regulated output power with a current of 800 mA. Its construction is “Open type” as it is home made. You can make it like a professional power supply by fixing inside a box with connectors for tapping the output.
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Relay for LED Emergency Light. Home Utility Circuit 26

1AWhy going for a complex circuit to make an Emergency Light automatic? Now different types of low cost Portable LED Emergency lights are available but these are not automatic in function. A Mobile charger like adapter is supplied along with these for charging. But we have to turn on / off the light manually using the switch. We can easily convert these kinds of Emergency lights into automatic so that when the power fails, the light turns on and when the power resumes, it turns off and enter into charging mode. We need only one relay and a diode for this. The advantage of the relay is that, full current will flow to the LED panel to get maximum brightness.
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Reality in LED Bulbs. Home Utility Circuit. 25

3AWe all use LED Bulbs to save energy. It is available in 3W, 5W,7W,9W,15,18W etc . What this Watt indicates? Is its Power output similar to CFL, Tube light etc or light intensity similar to CFL or Tube light? If you consider the specified watts as the real output, then it is a mistake because the Capacitor power supply used in LED bulbs cannot give the specified output. For example, a 9 Watt LED bulb shows that it is only 3.9 W both in theoretical calculation and in power measurements. Let us hack one LED Bulb to see how it is behaving.
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