The requirement and use of electrical energy is increasing rapidly with technology development and population growth. By using renewable and non-renewable sources, electrical energy is generated. Multiple advantages of solar energy are the key factors behind the usage of solar charge controller for various purposes in industrial applications. Solar charge controller is used for storing the electrical power in batteries which is generated with the help of solar panels and further it can be fed into loads.
A solar charge controller is basically a current or a voltage controller to charge the battery and to protect the cells from overcharging. It directs the current and voltage comes from the solar panels to charge the battery. Generally, 12V panels are put out in the approximate value of 16 to 20V, so in the overcharging condition the electric cells will be damaged if no regulation is provided. For getting completely charged, electric storage devices require14 to 14.5V. The solar charge controller circuits are available in all features, sizes and costs ranges from 4.5A to 60-80A.
Here in this article we are going to discuss about solar charge controller using comparators and as advancement to that solar charge controller circuit with microcontroller is also explained.
Solar Power Charge Controller Circuit using Comparators
The solar charge controller project is designed to store electrical energy in batteries which is obtained by converting the solar energy into electrical energy with the help of photo-voltaic cells during the daytime and to utilize this stored solar energy during night time. For monitoring the voltage and load current of solar panels a set of op-amps are used as comparators as shown in the block diagram.
Different types of light emitting diodes are used to indicate the following conditions: under voltage, overload and deep discharge conditions. To cut off the load in overload and low battery conditions MOSFET is used as a power semiconductor switch. If the battery is fully charged, then the solar energy is transferred to the dummy load with the help of a transistor. This project can be further developed by using microcontroller. So here we are explaining about the solar charge controller circuit using microcontroller
Solar Charge Controller Circuit using Microcontroller
Solar charge controller plays a prominent role in the solar powered lighting systems based on the system overall performance. Solar powered lighting systems are made available in urban and rural areas. These include solar street lights, solar home lighting systems and solar power packs. All these systems make use of four major components, namely photo-voltaic cells, solar charge controller, rechargeable battery and load.
Solar Charge Controller Circuit using Microcontroller Consists of Following Features:
- Automatic dusk to dawn operation of the load
- Overcharging condition
- Deep discharge condition
- Low current consumption
- Displays the status on LCD
The solar charge controller circuit diagram comprises of the following hardware components: AT89C2051 microcontroller, serial ADC0831, voltage regulator 7805, MOSFET, LCD display, and few discrete components such as solar panel, rechargeable battery, dusk to dawn sensor, charge control and load control.
Hardware Components Used
AT89C2051 Microcontroller: Microcontroller acts as the heart of the whole circuit.It has following specifications such as high performance and low voltage, and it has the following features: 2KB of flash, two 16 bit counters/ timers, 15I/O lines, a full duplex serial port, a five vector two level interrupt architecture, on chip oscillator, analog comparator and clock circuitry. A 12MHz crystal oscillator is used to provide the basic clock frequency. All the I/O pins get reset if reset pin goes high. For the manual reset operation switch S2 is used.
Serial ADC0831: Analog to digital converter and microcontroller are used for monitoring the battery voltage. It is an 8 bit successive approximation ADC converter with a serial I/O and very low conversion time of 32micro Sec. It is made available in an 8 bit PDIP package and interfaced to the microcontroller with the help of three wires.
Voltage Regulator 7805: It is an integrated circuit used to maintain the output voltage at a constant value. Many of the circuits have fluctuations and will not produce a fixed voltage in that case voltage regulator is preferred. It provides a regulated power supply of +5v to the entire circuit.
Dusk-to-Dawn Sensor: Generally in solar lighting system or solar street lights, during dusk time the light switches should be ON and switched off during the dawn time. During the dawn time the load is disconnected from the battery and battery is recharged with the help of current from the solar panel. A simple dusk to dawn sensor is built using a potential divider formed around Zener diode Z1, resistor R8 and R9 and transistor T1 to know the solar panel voltage by microcontroller. By the status of this sensor microcontroller decides whether the battery should be in charging or discharging mode or whether the load is to be connected to or disconnected from the battery.
Solar Panels: In this project solar panels are used to charge a battery and a range of wattage from 10 to 40 watts. Higher wattage panels are also recommended, but modifications have to be done to the charge controller circuit.
Rechargeable Battery: A 12V lead-acid battery is used to store the electrical energy comes from the solar panels. The capacity of current in ampere-hour ranges from 5Ah to 100Ah
LCD Module: LCD Display is used to display the battery voltage and system status. In this project a 4-bit LCD is used to save the microcontroller port pins. In 4-bit mode LCD is interfaced to the microcontroller by using 7 pins.
Circuit Working of Solar Charge Controller
- Microcontroller is powered up with 5V regulated DC supply from the battery. Ones the microcontroller is powered ON, it continuously monitors the battery voltage with the help of ADC. A potential divider connected at the pin 2 of the ADC with resistor arrangement, scale down the voltage from 0V-20V to 0V-05V. Then these values are accordingly displayed on LCD display.
- This circuit is implemented with a parallel regulation technique which allows the charging current to flow into the battery and once the battery is fully charged it stops charging. By making this charging as pulsed, wasting of current as heat is reduced to keep the battery topped-up.
- Microcontroller continuously gets the input signals from dusk to dawn sensor and based on this input, it switches the load or charging relay. When this sensor gives the input to microcontroller upon solar voltage presence, then microcontroller drives the LCD to display the message as charging. Once battery is fully charged (reaches to 14V), then microcontroller interrupts the charging by energizing the relay through the MOSFET. At this time, microcontroller starts 5 minute timer and displays the message as Battery Full.
- After the timer elapsed, the relay reconnects the battery to solar panel. By this way solar charging current is pulsed as long as the solar voltage is present.
- Whenever the solar panel voltage falls below the zener diode voltage of the dusk-to-dawn sensor, then microcontroller receives it and activates the load through MOSFET and accordingly displays the message as Load ON. Similarly, when the voltage falls below the 10V of the dusk-to-dawn sensor then microcontroller turns OFF the load through this MOSFET.
By this way solar charging system charges the battery as well as protects the battery and loads from over and under voltages. Hope this article gives a brief about the advanced solar charge controller circuit using microcontroller. For more information regarding the solar charger controllers and their detailed working you can contact us by posting your queries in the comments section below.
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