Solar Cell Circuits

Photocell power supply (MAX630)

This circuit delivers either 4.8 or 7.2 V regulated at 15 mA with a 3-V input from a bank of photocells. R1 should be 453 k? for a 7.2-V output and 274 k? for a 4.8-Vdc output. Regulator efficiency is around 70%. This should be considered when selecting suitable solar cells. ..

Digital Clock with Solar Regulator

The basic clock circuit (top schematic below) is similar to the binary clock (on another page) and uses 7 ICs to produce the 20 digital bits for 12 hour time, plus AM and PM. A standard watch crystal oscillator (32,768) is used as the time base and is divided down to 1/2 half second by the 4020 binary counter. One half of a 4013 data latch is used to divide the 1/2 second signal by 2 and produce a one second pulse that drives the seconds counter (74HC390 colored purple). The minutes are advanced by decoding 60 seconds (40 + 20) and then resetting the seconds counter to 0 and at the same time advancing the minutes counter. The same procedure is used to advance the hours. The second half of the 4013 latch is used to indicate AM or PM and is toggled by decoding 13 hours and resetting the hours to 0 and then advancing the hours to "one"...

Solar motor driver for small robots

Since you can only use motors and coils with this circuit robots built with this circuit are mainly mechanical such as my artistic butterflies. One other common use is a little thing called a symet which can roam around and not get stuck using only one motor. The solar cell starts charging the capacitor and the voltage rises. As soon as the capacitor reaches around 2.7v the 1381 turns pin 1 high and turns the 3904 ON. When the 3904 turns on it brings the base of the 3906 low which turns it ON. With the 3906 ON current is supplied to the base of the 3904 which keeps it ON. Now current can flow through the motor and it turns. When the voltage gets down to .7v the transistors turn OFF and the process is repeated...

Solar powered robot

Make your own solar powered robot at home using things you probably already have. Transistors, resistor, capacitor, solar battery and flashing LED are available at any electronic store, if you don't already have them. Solar cells out of calculators work as well, you might want to use more than one since they are really small. If you do, connect the positive wire from each solar battery together. A small motor should be used like the ones in walkmans. Solder everything together and watch it come alive. Put it under a light and let it charge, it should take couple seconds for each burst of energy. Works best in sunlight...

12V / 4A Solar cell regulator

When the panel isn't generating, the entire circuit is off and there is absolutely no current drain from the battery. When the sun gets up and panel starts producing at least 10 Volt, the LED lights and the two small transistors switch on. This powers the regulator circuit. As long as the battery voltage stays below 14V, the operational amplifier (which is a very low power device) will keep the MOSFET off, so nothing special will happen and the panel current will go through the Schottky diode to the battery...

Solar voltage regulator

The circuit presented here uses linear shunt regulation. Simply spoken, it burns off all excess energy from the panel, keeping output voltage constant. At times when the solar panel output is equal or greater than the load, and the battery is fully charged, the load gets its power from the panel, while the battery rests at full charge. Five years battery lifetime are entirely normal with this system, while the same batteries last only two to three years when used with pulsing regulators! The second responsibility of the regulator is watching over the battery voltage, and dropping off the load when the battery gets discharged too much. Lead batteries are severely damaged by deep discharges, so it's far preferable to drop off the load, then to have the battery die in a bad weather spell. ..

Solar Garden LED Lighting

The circuit consists of two stages. The first stage is a "switch" or cut-off device. It detects a voltage above 0.7v from the solar panel and the resistance between its collector-emitter terminals reduces to a very small value. The 10k resistor allows the voltage on the solar panel to rise above 0.7v during bright sunlight, while the 100k discharges the 100p when the voltage is very low and the capacitor holds a charge to keep the transistor turned on when the voltage is "high". When the resistance between the collector-emitter terminals of the first transistor is low, it is turned ON, and the second transistor does not get enough voltage on its base for it to operate as an oscillator...

Solar Charger II

This is another kit in our self-sufficiency range. We also have a 12v fluoro inverter kit for those who need to operate 20watt to 40watt fluorescent lamps from a 12v supply. We will be introducing a number of kits for those who have opted to live with 12v energy. With nearly everything electronic capable of operating from a 12v supply, there is no reason why anyone opting to live with a low voltage supply cannot enjoy all the electronic pleasures of those who live in the city. Some products are not yet available for 12v operation but inverters are available from 100watts to 4kw. ..

5v Regulated Solar Power Supply Circuit

This project uses the 1.2v rechargeable battery and solar panel from a Solar Garden Light. These lights can be bought for less than $5.00 in most $2.00 shops or similar shops that sell general household items. We are also using the housing for this project as we could not buy the case, battery and panel for $5.00 in an electronics shop. It is incredible that a solar panel, rechargeable battery and plastic housing can be bought for less than $5.00! We have already described the operation of the Solar Circuit, but unfortunately it cannot be used to generate a voltage higher than about 4v, so a new design had to be created. ..

Solar Charger circuit

Few years back, I had been working on a project for solar auto lighting. The light will turn on when the the solar panel voltage drop below a set point indicating that it is dark. The detection is done by using D2 in the schematic. The zener diode value will be adjusted so that the transition between the switch depends on the amount of light the panel receive. Relay K1 is used to switch the load and the battery. If the battery power fall below a set threshold, the relay will cut the supply to the load. Relay K2 is used to control the charging of the circuit. When a Set point is reach the charging will be cut off. A Comparator is used for the voltage comparison...

PIC16F84 Solar Charger

The previous version of this device used pulse width modulation (pwm) to control the power from the five solar panels to charge the battery bank. Under full sun conditions the MOSFETS got a bit warm and the whole unit radiated a lot of RFI. This design uses a set of relays - one for each panel. If the controller decides the battery voltage is too low, it engages another relay; if its too high, it drops one out. This tends to 'float' the voltage at about 14 volts as long as sufficient sunlight is available. ..

Self-Powered Solar Data Logger

My project is a self-powered solar data logger. Put out in the sunlight, it will measure the light level and log this to memory to be later downloaded to a computer. The system is powered by a small solar panel and battery. The solar logger I built uses a photodiode to measure the solar insolation level. It converts the analog signal from the photodiode to a digital value that is stored in flash memory. Every time the system logs a data point, it also logs the time and date so that the data can be analyzed in the future. The logged data is available for a user to download to a computer for analysis. While the system is logging, real time data is displayed on a small LCD screen as well as information about the battery voltage, the length of time the system has been logging and the length of time it can continue to log before running out of memory. ..

Solar Battery Regulator/Controller

In the actual device the transistors are bolted to the aluminium case. The schematic diagram shown here represents how the circuit would be built if all components were on-board. Separate paths for load current and voltage sensing allow the battery voltage to be measured accurately even under loads of several amps. The LM4041 provides an accurate low-power voltage reference for the sensing circuit. This 1.225V reference is used directly for the conventional lead-acid setting and via two alternative dividers for the sealed lead acid and lithium voltages. Using a 1% version for the voltage reference and 1% resistors in these dividers keeps us from going too far above the magic 4.1V limit on standard lithium cells without having a pesky trimmer, or worse, a set of trimmers...

Solar Powered Mailbox with PIC16F628

The purpose of this project is to develop a self sufficient Mailbox (real one) that will be powered only by the sun and that will display the number of the house, but only in accordance with the battery level. The system must work autonomously when there is or not enough light to charge the battery. The Mailbox is powered by a 5V/80mA Polysilicon solar cell. The sun energy is used to charge a 3 AA NiMH battery. At night, when there is no light, the PIC is driving the 3 Digit according with a sequence which is defined in its program given in Annex...

The design goals of this circuit were efficiency, simplicity, reliability and the use of field replaceable parts. A medium power solar system can be built with the SCC3, a 12V (nominal) solar panel that is rated from 100 milliamps to 20 amps, and a lead acid or other rechargeable battery that is rated from 500 milliamp hours to 400 amp hours of capacity...