Technology does not stand still. This electronic thermometer circuit that display by LED 20 level and The peripheral Bells Alarms. When the temperature reaches the preset value. On a daily basis. We have to work a lot. If someone would have noticed and remind us always. To the dangers of heat would be good, no less. This project was an assistant we would recommend is The Electronic Thermometer LED display and versatile control sure enough.
The idea starting from when measure temperature And display the various temperatures with LED. If we are away from the circuit. If the temperatures as high as is harmful. Or need to report that. Go to settings. It has to be part of the alarm circuit is connected to the circuit. The purpose of this project was to these already.
The working printciple
In circuit figure 1 is a guard (sensor) acts always check the temperature is Thermometer (TH1) Which is a resistor that changes value based on temperature. Thermistors are a number TD5-C310D is the NTC. Resistance changes with temperature in all three degrees higher. At room temperature (25 degrees Celsius), so the resistor 10K ohm.
The start of the power supply circuit, from AC-power 220V through a fuse (F1) of 500mA come to a transformer T1 to reduce a voltage is 9 volts. There is C3 act cut a noise signal. And capacitor C4 is filter to smooth signal.
Then so send signal to IC3 to Maintain a constant DC voltage at 9 volts. To supply to the Electronic Thermometer circuit.
The main principle is at the IC1 and IC2 number are LM3914, which is the meter IC has the output of10 pins, by the input ?? 5 of both IC connected together. To get voltage of TH1 temperature sensor, which is connected in series with R4. To lead voltage drop across R4 is supplied to pin 5 of IC1 and IC2 by TH1 on the more resistance. Voltage drop across R4 will be less valuable. and when TH1 with less resistance. Voltage drop across R4 is added. If this is the control voltage of the LED lights to indicate the temperature.
Changing voltage at pin 5 will be in the range 1 to 6 volt. Properties of the thermistor used in this circuit. We define a temperature in the range of 0 to 60 degrees Celsius. So every 3 degrees Celsius temperature, will has the voltage changes in the pin 5 about 0.25 volt. And has one The LED lit up.
When the TH1 is heated, the voltage at pin 5 will increase up, Sequence of LED will light up. For example: The voltage from pin 5 is equal to 3 volts to the LED brightness has 8 LEDs. But if get voltage is 3.5V Light 10 pieces, etc.
Figure 1 The Complete circuits of The Electronic Thermometer LED display and versatile control.
In Figure 1, we show that IC2 results in 3 to 30 degrees Celsius during the LED1 to LED10 and the temperature 33 to 60 degrees Celsius display the LED11 to LED20 IC1, respectively. For example, if the temperature of the air at a temperature of 27 degree Celsius, it will have to LED9 LED1 light, and VR1 can be adjusted to match the temperature measured by the thermometer. By changing the voltage of the pin in the middle of it. When rotated at pin 6 of IC1.
As usual at the output pin of IC1 or IC2 is connected to the cathode polarity of LED relative to the ground. Are high enough to not cause LED brightness. When the IC has comparing voltage internal until that pin lit up. If we connect the output pin to activate it, it makes the transistors Q1 to Q1 run (on). has current flow from the positive voltage through Q1 go to provide to a relay. Makes relay contacts are connected. When connected bring a signal generator, an audio alert when temperature rises to the point where we set up it.
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