LED Panel Emergency Lamp. Home Utility Circuit 21


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You can make an LED Emergency lamp easily using the LED Panel available now. The lamp turns on when the power fails and turns off when the power resumes. When the mains power is available, the 12 V 7.5 Ah battery charges. Since LED panel is used, the emergency light can have a back up time of many hours. You can make 9 Watt or 18 Watt Emergency lamp using the circuit presented here.Its Backup time will be 10 Hours.Its cost will be around Rs. 950. Of these, the battery alone costs Rs.800. If properly maintained, the battery will last more than 4 years.

Designed and developed by D.Mohankumar

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Battery Monitor. Home Utility Circuit 14


Battery-Monitor-1Most of the Surveillance systems and CCTV camera uses rechargeable 9 volt battery. This simple Battery Monitor can be hooked to the 9 V battery so that it indicates the voltage in the battery through visual indications. When the Test switch is pressed, the Bicolour LED lights as Green if the battery voltage is above 9V (fully charged) , it lights Yellow when the voltage is between 7.5V and 9V, ( moderate charge ) and lights Red when the battery voltage is below 7.5 ( needs charging ).
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Battery Charge Indicator. Simple Design 5


BATTERY-CHARGE-INDICATOR-2This is one simple but highly useful circuit for you. Most of us use different types of Rechargeable batteries in Portable devices, Inverter, Emergency lamp etc. If the battery is deeply discharged, sometimes it will not get fully charged later. This is the most common reason for the failure of Emergency lamp. So we need an indicator to show the safe level of battery voltage. It is too simple to make it and needs only three components. Just hook up it in the battery and it will remind you when it needs charge.
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Voltage Monitor for Solar Panel. Design Note 46


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Here is a simple circuit to monitor the voltage level in Solar panels. Usually a volt meter test is done during the installation of solar panel and then after, the panel remains unattended. If the solar panel is not providing sufficient voltage for charging the battery, that will permanently destroy it. A 12 volt Solar panel gives maximum of 22 volts DC in bright sunlight, which drops to around 16 volts when the load is connected. So a voltage level around 16 volts is necessary for charging the 12 volt Lead Acid battery. But the voltage output from the solar panel may reduce due to the accumulation of dust on the panel and corrosion of terminal contacts. These remain unnoticed ,so only when the battery fails ,we note this. This simple circuit solves the problem. If the solar panel  gives above 15 volts with the battery connected, the LED remains off. When the voltage from solar panel drops below 15 volts, LED turns on to indicate low voltage. This usually happens when the sunlight is low, but if the LED remains on in bright sunlight also, it indicates low output from the solar panel. The circuit can also be used as Battery level monitor.
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