The project posted here is a 3000W inverter with the facility like inbuilt charger, over and under voltage control, temperature control, microcontroller based etc. We all know that inverter is a device that change DC power into AC power (just opposite of rectifier). General purpose inverter (low or medium power inverter) used in our house converts 12V DC voltage to 220V AC. But the circuit posted here convert 24V DC (two 12V battery connected in series) to 220V AC.
Circuit Description of Microcontroller Based 3000W Inverter with inbuilt charger
For better description the circuit of Microcontroller Based 3000W Inverter with inbuilt charger is divide into two main sections.
- The inverter sections
- Microcontroller section
Inverter Section: Figure 1 shows the main circuit diagram of inverter circuit. This section converts 24V DC to 220V AC and also charge the battery connected. This circuit is further into five different sub sections.
- Astable Multivibrator
- Inverting Circuit
- Automatic Change Over Unit
- Charge Regulator
Astable Multivibrator: Astable multivibrator is a device which oscillate continuously in a quasi-stable state without any external excitation. The circuit of stable multivibrator is designed using a CMOS IC CD4047. The output frequency of this multivibrator is depends upon time constant and is always 1800 out of phase with each other. Variable resistor VR6 is used to adjust the output frequent at which it oscillates. For the design published here variable resistor VR6 is so adjusted that the output will be 50Hz pulse width modulated signal. The two outputs from pin 10 and pin 11 is used to control the two individual MOSFET networks for inverting process.
Inverting Circuit: The inverting circuit is designed using series of MOSFET IRF150. This series is arranged in two parts as shown in figure 1. Both the arrangements are open and close alternately at regular interval of time because two individual output of IC4 (CD4047) is connected to the gates of individual arrangement. The Drain of both arrangement is connected to the upper and lower limb of centre tap transformer X1 as shown in figure 1. When one arrangement is switch on other will be switch off and vice-versa, thus alternating voltage is produce. This section determines the power of inverter. According to the above arrangement the output power is about 3000W.
Automatic Changeover Unit: The automatic changeover unit is designed using 5 individual relays (RL1 through RL5) as shown in figure 1. Transformer X2 with bridge rectifier is used to power the relay circuit. All the input of these relay is connected to the output of bridge rectifier BR2 thus, when mains input is available at the input port all these relay (RL1 to RL5) start to energize. The energized electromagnetic pull the metal base connected with N/C to N/O. Relay RL1 control input and output of inverter. Relay RL1 provide LIVE line where neutral is provided by relay RL3 and RL4. Relay RL2 provide charging voltage when mains is available.
Charge Regulator: Charge regulator circuit is designed using op-amp LM393 which basically compare the battery voltage. When voltage of battery is fully charged i.e. reaches up to 26.5V to 27.5V, the output of become high as a result transistor start to conduct and piezo buzzer start to beep. This beep sound indicates that the battery is fully charged.
Microcontroller Section: Microcontroller Section is built around AT89C2051 is shown in figure 2 which is basically used as indicator circuit and temperature control unit i.e. used to display under or over voltage and also operate fan when temperature rises above preset level i.e. 500C.
Temperature monitoring and controlling section is designed using a thermistor. When the temperature of unit exceeds preset level, voltage of thermistor exceed then voltage available at non-inverting input thus output of comparator IC LM393 (IC2:B) become low as a result switch on the 12V DC fan and also make pin P1.2 high (indicates temperature is high).
When the battery voltage decreased to 18V DC the comparator output (IC2:A) becomes low as a result Piezo buzzer PZ1 start to beep which indicate battery is low and need charge.
SOFTWARE: The software is written in C programming language and compiled using keil software. You can directly download and use software from below.
PARTS LIST OF MIROCONTROLLER BASED 3000W INVERTER WITH INBUILT CHARGER
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1, R2 = 330Ω
R3, R4 = 2.2 KΩ
R5 – R7 = 3.3 KΩ
R8 – R16 = 1 KΩ
VR1 – VR5 = 10 KΩ
VR6 = 50 KΩ
|C1, C2 = 33pF
C3 = 0.1 µF
|IC1 = AT89C2051
IC2, IC6 = LM393
IC3, IC5 = 7805
IC4 = CD4047
T1 – T3 = 2N5086
T4 – T11 = IRF150
D1, D2 = 1N4004
D3, D4 = MURB1620CTR
D5 – D9 = 1N4001
BR1 = 1200V, 50A Bridge Rectifier
BR2 = 50V, 6A Bridge Rectifier
LED1 – LED4 = 5mm Any Color LED
RT1 = PTC Nickel Thermistor
|TR1 = Primary and Secondary Center Tap Transformer
TR2 = 220V primary to 15V, 500mA secondary step up transformer
RL1 – RL5 = 12V Relay
SW1, SW2 = ON/OFF Switch
PZ1, PZ2 = Piezo Buzzer
FAN1 = 12V DC Fan
X1 = 12MHz