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Automatic Temperature Controlled Switch

We can make control temperature using this circuit; it will make control temperature automatically. LM35 is the temperature sensor used in this circuit for detection of temperature and also it helps to turn ON/OFF the output devices or appliances.
Once we tune the LM35’s sensitivity level of temperature, the circuit becomes control as an automatic switch. Easily available components can be used for developing this circuit prototype with small PCB boards like line/dot PCBs.

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Circuit

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Construction & Working

Regulator unit and rectifier are the first stage of this circuit. 110V to 220V AC Supply is the input voltage and it is converted into 9V AC by using step-down transformer. After that, it is being rectified into DC voltage using bridge rectifier. Capacitor C1 reacts as filter to remove AC ripples then using 7805 regulator IC regulates provides constant 5V DC Voltage Supply.
LM35 is the temperature sensor used in this circuit and it gives an output voltage linearly proportional to the centigrade temperature. And an operational amplifier LM358 used here to help us to choose the temperature level through the variable resistor, VR1 and output of this Op-Amp is drives the transistor, Q1. In between +5V DC and collector terminal of the transistor Q1, the relay coil has been connected. When output voltage is higher than 2.5V from Op-Amp transistor Q1 turns ON and it connect the relay coil to neutral/ground. Hence, the coil gets power and makes the Normally-Open contact to Normally-Closed one. So, we can control electrical loads or an appliance automatically depends on temperature.

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12v-inverter

12v to 220v inverter DIY circuit

Inverters are made for producing high voltage from low voltage DC sources/batteries. We are here to design an inverter circuit for converting 12V DC source into 220V AC power. Its components are easily available in our electronics markets and so easy to build on PCB boards.

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Operations of this kind of inverters are based on switching pulses and were uses step-up transformers. So, the CD4047 microcontroller acts as a switching pulse oscillator and IRFZ44N (N-channel power MOSFET) acts as it’s switch. Then the 12-0-12 secondary transformer will inversely used as a step-up transformer.

Inverter Circuit Diagram

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Components Required

  1. Micro-controller CD4047
  2. Power MOSFET IRFZ44 = 2.
  3. 12-0-12V secondary transformer 1 amps
  4. Variable Resistor 22KΩ
  5. Resistors 100Ω / 10 watts = 2
  6. capacitor 0.22µF
  7. 12 volt battery
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Construction & Working

This inverter circuit has switch device and step-up transformer. As per the theories, high switch frequency pulse reaches the step up transformer and due to the mutual inductance; output voltage will reach high value.

The microcontroller CD 4047 is configured as an astable multi-vibrator mode with the help of variable resistor RV1 and capacitor C1. By varying the value of RV1, we will collect different range of output pulse at Q and Q’ pins. These all results the variation of output voltage at the step-up transformer.

The IRFZ44 (N-channel power MOSFET) will drain, pins are connected with secondary pins of the transformer and common pin connected with the secondary winding and is connected with battery positive bias. Both MOSFETs source pins are connected to the negative bias of battery. And these are driven by Q and Q’ output from CD4047 micro-controller. If an alternate square pulse drives the MOSFETs switches, the secondary winding may forced to induce alternate magnetic field. This magnetic field induce primary winding of transformer and will produce high alternate voltage.

Note: High AC voltage circuit. Attention for handle with extreme care.

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