Once I purchased a China make AC-DC LED emergency lamp for Rs.70. I wonder ,how they are selling the device cheaply. Due to curiosity, I opened the case of thelamp. So simple circuit that cost only Rs.20, a small 6 volt battery and LEDs. This is the reason why they are selling the device at low cost. Reliability? Sometimes it will last years, otherwise few days. That depends on the use and conditions. Most of the China make devices use tranformerless power supply which can damage when spikes appear in the mains lines. Any way, simplicity and low cost can be considered. I have drawn the diagram and constructed one sample. It is still working. Let us see the circuit.

DC Mobile Charger. Utility Gadgets .11

You can use this simple Mobile charger using 6 volt Emergency lamp battery. Take an out from the Emergency lamp battery using a Mono jack socket and plug in this charger into it using a Jack. On the other end, connect it to the mobile phone using a suitable jack. Full safe, no damage due to power line spikes, lightning etc. It also drains the emergency lamp battery which is good for its life because it is sleeping most days without use. You can also use the same circuit for 12 volt car battery .

Regulated charger with Backup. Utility Gadgets.10

Here is a Battery backup circuit with regulated charger. The circuit immediately takes the 12 Volt load in the event of a mains failure. The circuit also has a constant voltage and current regulation section and a battery full indicator. This kind of circuit is used in UPS and Inverter. The circuit is designed for 12 volt battery but it can be used for 6 volt battery also with slight modification

An Inverter circuit converts DC to high volt AC for driving high power devices. The principle of simple emergency lamp circuit and the heavy load inverter circuit is the same. The DC voltage is converted into AC using an oscillator circuit. A driver transformer then step up this low voltage AC to 230 volt AC. The output waveform from the oscillator depends on the type of circuit. In simple inverter, it is square wave but in microprocessor based types, it may be quasi sine wave or pure sine wave. Pure sine wave AC is similar to the AC available in the mains power supply so all the instruments usually running in Mains power can be connected in Pure sine wave inverter. The appliances connected to Square wave and quasi sine wave may not work well as seen in the humming of fan, flickering of tubes etc. This circuit is meant for explaining the method of Â an inverter.

Here is a Boost charger to start vehicle if the battery is down. Just connect the charger to the battery terminals (in the connected position) and start the vehicle. It will immediately charge the battery and the vehicle will start. Once the vehicle is started, the current from Dynamo will charge further. You can then disconnect the charger. It is an ideal charger to keep in the vehicle to avoid confusion due to vehicle breakdown related to battery problems. It delivers 15 volt DC and 10 Amps current for the boost charging. Partially discharged battery takes very long time from 24 to 48 hours to attain full charge. A boost charging will speed up the charging process and trigger the chemical reaction within the battery. So if the inverter or car battery is not accepting charge, it is ideal to boost charge for 1 hour and then charging with low current as usual.

A very good Tip to start a breakdown vehicle due to battery failure is added. See how it works.

High Current Charger with Cut Off. Utility Gadgets.7

Many of my readers require a High current battery charger with battery protection facility. So I am posting this circuit for charging 12 volt Lead Acid battery using Mains power. The same circuit can be connected to Solar panel also. The circuit has features like
1. High current charging
2. Voltage regulation
3. Current regulation
4. Full charge cut off
5. Battery protection
6. LED status indicators