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Solar Cell Voltage Regulator(BC547B)

2017-08-07 20:58  
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This article describes the Solar Cell Voltage Regulator (BC547B). The principle is very simple, very practical. The circuit components can help you understand better grasp this principle. For example, in this circuit, you can go to find and buy these components: BC547B.

This device is designed to be a simple, inexpensive ‘comparator’, intended for use in a solar cell power supply setup where a quick ‘too low’ or ‘just right’ voltage indicator is needed. The circuit consists only of one 5V regulator, two transistors, twoLEDs, five resistors, two capacitors, and one small battery. Although a 4-V battery is indicated, 4.5 V (3 alkalines in series) or 3.6 V (3 NiCd cells in series) will also work.

The specifications of voltage regulator IC1 are mainly determined by the size and number of the solar cells and the current pull of the equipment connected to the output. Here the low-drop 4805 is suggested but other regulators may work equally well as long as you observe the output voltage of the solar cells. Transistors T1 and T2 are complementary types i.e. one each of the pnp and npn variety.

Figure:1 Solar Cell Voltage Regulator Circuit Diagram

Figure 1 Solar Cell Voltage Regulator Circuit Diagram

Although the ubiquitous BC557B (pnp) and BC547B (npn) are indicated, any small-signal equivalents out of the junk box will probably do. The values of voltage dividers R1/R6 and R3/R4 may need to be adjusted according to the type of transistor and its gain, or according to the desired voltage thresholds. Using the resistor values shown in the schematic,LEDD2 turns on fully when the voltage is just above 5 volts.

LEDD1 turns on when the voltage drops below 4.2 volts or so. Between those two thresholds, there is a sort of no man’s land where bothLEDs are on dimly. A buzzer or other warning device could be connected across the terminals ofLEDD1 to give a more substantial warning if the voltage drops below operating limits. The current consumption of the circuit is about 20 mA at 5 V, and it decreases with the voltage supplied by the solar cells.


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