Simple Solar LED Light Circuit

The following easy solar light circuit is made for charging a battery pack for the duration of day time or so long as the solar panel is producing electricity, as well as for lighting up a coupled LED as the panel is not operative.

In one of my former write-up that discussed a straightforward solar garden led light circuit, we applied just one transistor for the switching functioning,

One particular issue with the earlier design is actually, will not offer a controlled charging for the battery, eventhough it not necessarily is likely to be totally crucial considering that the battery will never be charged to its 100 % potential, this particular feature may need much better.

An additional related problem with the earlier circuit is it has the reduced power specialization which will eliminate it from applying high power batteries and LEDs.

The below circuit successfully handles equally the above couple of challenges, through a relay and a emitter-follower-transistor stage.

While in ideal sun light, the relay receives ample power with the panel and continues to be switched ON using its N/O contacts turned on.

This lets the battery to acquire the charging voltage via a transistor emitter follower voltage regulator.

The emitter follower layout is designed with a TIP122, a resistor and a zener diode. The resistor offers the essential biasing for the transistor to run, as the zener diode number clamps the emitter voltage so as to ensure that it is controlled at just under the zener voltage value.

The zener value is as a result suitably decided to fit the charging voltage of the attached battery.

Emplyoing a 6V battery, the zener voltage could possibly be determined as 7.5V, pertaining to 12V battery the zener voltage may very well be close to 15V etc.

The emitter follower furthermore ensures that the battery will never get overcharged over a issued charging restriction.

While in night time, if a substantive decrease in sunlight is recognized, the relay is inhibited from the demanded minimal retaining voltage, triggering it to switch from its N/O to N/C contact.

The above mentioned changeover quickly changes the battery across charging mode to the LED mode, lighting the LED from the battery voltage.

Bill of materials to get a 6V/4AH solar light circuit employing a 1 watt LED

Solar Panel = 12V, 800mA
Relay = 6V/300mA
Rx = 10 ohm/2 watt
zener diode = 7.5V, 1/2 watt