Battery Chargers. Design Note 32


IMAGEPresenting here three circuits to make efficient Battery chargers. The 12 volt Lead Acid Car battery requires high current for fast charging. If we provide high current, the battery will charge within 1-2 hours fully. Usually a Lead Acid battery takes high current initially, which drops to 500 mA or less after 10-20 minutes. As a rule, it is advisable to charge the battery with a current that is 10 times lesser than the battery capacity. The Car battery is 32 Amps or 45 Amps so it requires 3.2 Ampere and 4.5 Ampere current respectively. So the charger should provide 14 volts with a current of 5 Amperes.

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Automatic Lamp


Here is a possible solution to prevent the wastage of energy if you forget to switch off the bathroom or terrace lamp. Once it is switched on, it stays on for 22 minutes and then automatically turns off. The lamp will turn on only if the switch is turned off and turned on again.Save Energy. It is precious.

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Long range uPD6121 IR Transmitter


Here is a long range Digital IR transmitter. It is a precision IR transmitter suitable for TSOP 1738 IR receiver module. Unlike other IR transmitters, this circuit is highly reliable and gives fail proof operation.

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Personal Alarm


If you feel threatened or need an urgent support in a crowd, use this alarm to catch the attention of others. It generates a loud siren simulating that of the Fire brigade which is enough to get support from others. A single press on the switch can activate the siren for 2 minutes and then it automatically stops. It is too small enough to keep in the pocket or hand bag.

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Bread board Regulated Power Supply


You can use this multi voltage power supply for the bread board projects. Most of the circuits require regulated power supply for errorless operation. This power supply can give regulated 12V, 9V, 6V and 5 V. Charger point for battery charging and Test point for LED and Buzzer are also included.

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Trick to detect Electronic Smog


Electrons are invisible to human eye then how can we see the electronic smog existing in our home. Is there any method to see them? Impossible, the only method is to capture the energy from it to activate a circuit for giving a visual indication. When you sit in front of a computer or television, you are being bombarded by harmful waves quietly emanating from it. Even if you turn off the device, your biomagnetic field is still bombarded 24 hours a day, 7 days a week by the EM radiations from power cables, electric and electronic instruments etc. These radiations of different frequencies exist in our environment as Electronic Smog. Extremely low frequencies waves (ELF) exist wherever electricity flows and radiate it from every electrical item in your environment. Let us try this circuit to give a visual indication of the electronic smog.

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Unusual LED Indicator


Here is an Unusual LED indicator for the Battery. It turns on fully when the battery voltage is above 13 volts and starts to blink faintly when the voltage drops below 12 volts .Finally the LED turns off  when the voltage drops below 10 volts. Its design is unusual because the LED driver transistor is connected in an unusual way.

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