Tuesday, October 9, 2012
Monday, October 8, 2012
Symple Solar Tracking System
Generally, solar panels are stationary and do not follow the movement of the sun. Here is a solar tracker system that tracks the sun’s movement across the sky and tries to maintain the solar panel perpendicular to the sun’s rays, ensuring that the maximum amount of sunlight is incident on the panel throughout the day. The solar tracker starts following the sun right from dawn, throughout the day till evening, and starts all over again from the dawn next day.
Fig. 1 shows the circuit of the solar tracking system. The solar tracker comprises comparator IC LM339, H-bridge motor driver IC L293D (IC2) and a few discrete components. Light-dependent resistors LDR1 through LDR4 are used as sensors to detect the panel’s position relative to the sun. These provide the signal to motor driver IC2 to move the solar panel in the sun’s direction. LDR1 and LDR2 are fixed at the edges of the solar panel along the X axis, and connected to comparators A1 and A2, respectively. Presets VR1 and VR2 are set to get low comparator output at pins 2 and 1 of comparators A1 and A2, respectively, so as to stop motor M1 when the sun’s rays are perpendicular to the solar panel.
When LDR2 receives more light than LDR1, it offers lower resistance than LDR1, providing a high input to comparators A1 and A2 at pins 4 and 7, respectively. As a result, output pin 1 of comparator A2 goes high to rotate motor M1 in one direction (say, anti-clockwise) and turn the solar panel.
When LDR1 receives more light than LDR2, it offers lower resistance than LDR2, giving a low input to comparators A1 and A2 at pins 4 and 7, respectively. As the voltage at pin 5 of comparator A1 is now higher than the voltage at its pin 4, its output pin 2 goes high. As a result, motor M1 rotates in the opposite direction (say, clock-wise) and the solar panel turns.
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| fig1 |
Fig. 1 shows the circuit of the solar tracking system. The solar tracker comprises comparator IC LM339, H-bridge motor driver IC L293D (IC2) and a few discrete components. Light-dependent resistors LDR1 through LDR4 are used as sensors to detect the panel’s position relative to the sun. These provide the signal to motor driver IC2 to move the solar panel in the sun’s direction. LDR1 and LDR2 are fixed at the edges of the solar panel along the X axis, and connected to comparators A1 and A2, respectively. Presets VR1 and VR2 are set to get low comparator output at pins 2 and 1 of comparators A1 and A2, respectively, so as to stop motor M1 when the sun’s rays are perpendicular to the solar panel.
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| fig2 |
When LDR2 receives more light than LDR1, it offers lower resistance than LDR1, providing a high input to comparators A1 and A2 at pins 4 and 7, respectively. As a result, output pin 1 of comparator A2 goes high to rotate motor M1 in one direction (say, anti-clockwise) and turn the solar panel.
When LDR1 receives more light than LDR2, it offers lower resistance than LDR2, giving a low input to comparators A1 and A2 at pins 4 and 7, respectively. As the voltage at pin 5 of comparator A1 is now higher than the voltage at its pin 4, its output pin 2 goes high. As a result, motor M1 rotates in the opposite direction (say, clock-wise) and the solar panel turns.
Similarly, LDR3 and LDR4 track the sun along Y axis. Fig. 2 shows the proposed assembly for the solar tracking system.
Thursday, September 27, 2012
USB Powered Lamp
This white LED lamp lets you use your PC or laptop at night without disturbing others’ sleep. It produces a soft white light just enough to see the keyboard in darkness as well as when the ambient light is poor during daytime. The circuit is powered by regulated 5V DC available from the USB socket of the PC.
LDR1 acts as a light-dependent switch to turn on the lamp (LED2 through LED7) when the ambient light in the room drops below the preset level. Transistors T1 and T2 (BC547) are used to switch on the lamp. The base of transistor T1 is connected to the voltage divider comprising LDR1 and preset VR1.
When light in the room is sufficient, the resistance of LDR1 is low. This results in a high voltage at the base of T1, driving it into saturation. When transistor T1 conducts, transistor T2 is cut off. This disconnects the power supply to all the white LEDs (LED2 through LED7). LED1 (green LED) glows as it is forward-biased, indicating the standby mode.
When it is dark, or the ambient light in the room is lesser than the pre-determined level set by VR1, transistor T1 is cut off and T2 conducts. All the white LEDs glow with sufficient brightness as these are connected to the power supply through series dropper resistors R2 through R7. These resistors are used to limit the current through white LEDs to a safe level.
LDR1 acts as a light-dependent switch to turn on the lamp (LED2 through LED7) when the ambient light in the room drops below the preset level. Transistors T1 and T2 (BC547) are used to switch on the lamp. The base of transistor T1 is connected to the voltage divider comprising LDR1 and preset VR1.
When light in the room is sufficient, the resistance of LDR1 is low. This results in a high voltage at the base of T1, driving it into saturation. When transistor T1 conducts, transistor T2 is cut off. This disconnects the power supply to all the white LEDs (LED2 through LED7). LED1 (green LED) glows as it is forward-biased, indicating the standby mode.
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