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This circuit (Fig 1 and Fig 2) is one I have used extensively with students in the teaching of alternative energy and gives practical experience of a voltage divider (can you spot it?).
It was originally modified from a garden solar light although I have increased the output current by using two BC548B transistors (how do you think I have done this?).
Although there are many ways to achieve the same result (you may wish to investigate and compare circuits), including the use of phototransistors, experience has shown that this circuit is reliable and provides enough energy to power strings of flashing LED’s if so desired.
This circuit will give you the chance to practice using a digital multimeter by checking the voltage of the Photovoltaic Cell (sometimes called solar panel or PV Cell) in various light conditions as well as checking the current levels within the circuit.
You may also wish to replace the 10K resistor with a variable resistor, this will allow you to change the activation light level.
You MUST always use Rechargeable Batteries in this circuit (unless you disconnect the PV Cell). I use Nickel Metal Hydride (NiMH) up to 1300mAh as I have found that anything above this level can result in battery damage in intense sunlight. You may need to experiment with the type of solar panel but I have used a 5V 70mA PV Cell.
It was originally modified from a garden solar light although I have increased the output current by using two BC548B transistors (how do you think I have done this?).
Although there are many ways to achieve the same result (you may wish to investigate and compare circuits), including the use of phototransistors, experience has shown that this circuit is reliable and provides enough energy to power strings of flashing LED’s if so desired.
This circuit will give you the chance to practice using a digital multimeter by checking the voltage of the Photovoltaic Cell (sometimes called solar panel or PV Cell) in various light conditions as well as checking the current levels within the circuit.
You may also wish to replace the 10K resistor with a variable resistor, this will allow you to change the activation light level.
You MUST always use Rechargeable Batteries in this circuit (unless you disconnect the PV Cell). I use Nickel Metal Hydride (NiMH) up to 1300mAh as I have found that anything above this level can result in battery damage in intense sunlight. You may need to experiment with the type of solar panel but I have used a 5V 70mA PV Cell.
In addition to a Prototype board (Breadboard), wire for connections and a power source, you will need the following components to build this circuit:
1 x 10KΩ Fixed Resistor1 x 5V 70mA PV Cell2 x 1.5V (or 1.2V) AA or AAA NiMH Rechargeable Battery with Battery box1 x Miniature LDR2 x BC 548B TransistorsLED's of your choice. I have used two flashing green LED's connected in parallel in this example.
1 x 10KΩ Fixed Resistor1 x 5V 70mA PV Cell2 x 1.5V (or 1.2V) AA or AAA NiMH Rechargeable Battery with Battery box1 x Miniature LDR2 x BC 548B TransistorsLED's of your choice. I have used two flashing green LED's connected in parallel in this example.
Fig 1
Fig 2
The PV cell allows current to flow through the diode when in sunlight. This in turn recharges the battery.
The diode stops any current flowing back from the battery which could damage the PV cell.
The diode stops any current flowing back from the battery which could damage the PV cell.
Solarcharger
Basic Transistor Circuit Software Simulation
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