How to Make temperature tolerance checking system

You went to make a temperature tolerance checking system circuit using IC LM3914, NE555, temperature sensor LM35 to make a circuit. The circuit used temperature-tolerance limit checking. Most of the instruments and machines used in industries and research laboratories have a temperature-tolerance limit and here we can use this circuit for temperature tolerance limit checking.

≡ Component and working details:

  • Resistors: In this circuit, we use 150 ohms, 470 ohms,1k,1.5k, 2.2k, 10k, 30k, 47k resistors and 1k,4.7k,330k VR.
  • Capacitor: Capacitor two-terminal electrical component and it used to store electrostatic energy in an electric field. In this circuit we use 0.1uf, 1uf, 10n,10uf
  • Transistor: In this circuit, we use a BC548 transistor. It’s a general-purpose BJT NPN Transistor. BC548 transistor has 3 pins 1-Collector, 2-Base, 3-Emitter. Current flows in the collector, the biasing of the transistor are controls by the Base, Current Drains out through the emitter.
  • NE555(Timer IC): In this circuit, we use two NE555 IC. In this IC is available 8 pins . 1 pin used to ground, 2 pin is a trigger, 3 is used to an output pin, 4 is the reset pin, control voltage pin is 5, 6 is the threshold pin, 7 is the discharge pin and 8 number pin is used to +Vcc. NE555 IC power supplies ranging from +5V to +18V.
  • Temperature sensor LM35: In this circuit, we can use the LM35 IC as a temperature sensor. LM35 outputs an analog signal which is proportional to the instantaneous temperature. The most important advantage of LM35 over thermistor is it does not require any external calibration.
  • IC LM3914: In this circuit using LM3914 IC. It can drive LEDs like a display. It can be expandable up to 100 displays. This IC has 18 pins. Pin 1,10,11,12,13,14,15,16,17,18 is LED operated pins. Pin 2 is ground, Pin 3 is Vcc, Pin 4 is RLO, Pin 5 is signal, Pin 6 is RHI, Pin 7 is Ref out, Pin 8 Ref Adj, Pin 9 is Mode. this IC supply voltage ranges from 3V-18V.
  • LED: A light-emitting diode(LED) semiconductor light.


≡ Circuit And PCB:


temperature tolerance checking system
Temperature tolerance checking system Circuit
Temperature tolerance checking system
Temperature tolerance checking system PLC

≡ How to work this circuit :

This circuit used for the temperature tolerance checking system. This circuit used temperature sensor LM35, this sensor checks the temperature and throw signal in IC LM3914. LM3914 IC has checked the temperature range and show the output in LEDs. When the temperature range becomes high then the IC LM3914 Pin10 throws a signal in the IC NE555. Two NE555 ICs have used, the first NE555 configured as a monostable multivibrator, LED10 glows maximum tolerance limit. As a result, output pin3 of NE555IC goes high to enable and throw a signal in the second NE555 IC and NE555 generates a frequency at its pin 3 that drives the transistor . The transistor in turn drives an 8-ohm loudspeaker to produce audible sound. Again, When the temperature is normal range then the loudspeaker is off.

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Md Shoriful Islam
group leader mechatronicslab

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