Many Electronic circuit projects in simple ways of learning

Temperature detector circuit with buzzer alarm

You are boiling hot water. How it alarms when 40 degrees Celsius. You should build the simple temperature detector circuit diagram with a buzzer alarm. It can check a changing of temperature. It is so real easy project.

Also, you can apply them to various temperature detectors. For example
Heat – cold water and many others. Follow imagine yourselves.

How does it work
Figure 1 shows the circuit diagram. In circuit has main components.

First of all, R1 limits the current to about 1 mA to IC1(LM335Z).

temperature detector circuit
Figure 1 temperature detector circuit diagram

Then, VR1 adjusts an output voltage to pin 2 (inverting) of IC2.

While, the R2, VR2, R3 are the reference voltage to the comparator at pin 3 (non-inverting). Both resistors R2 and R3 are a voltage divider. And the VR2 adjusts the voltage or the sensitivity of the temperature detector.

The voltage across VR2 is in a range of about 2.8 to 3.3V. Which it is comparable to the temperature range of about 268 to 337 degrees Kelvin, or -5 To 64 degrees Celsius.

You can set the temperature according to want. Since the temperature sensors IC1 can apply from -40 to +100 degrees Celsius.

For VR3 adjust the offset voltage of the input to IC2 (TL071C). To get the output voltage at pin 6 is 0 volts. When input voltage at pin 2 and pin 3 is the same value.

We come back to see it works.

When IC1 detects a temperature less than the VR1 setting. It makes the input voltage at pin 3 more than the voltage at pin 2.

Thus, the output voltage out of pin 6 to be high, to close about 9 volts. This causes Q1 to switch off and buzzer will sound off.

If the temperature starts into higher than the preset value. The voltage is at pin 2 will be more than at pin3.

Thus, the voltage at pin 6 is lower or around 1.3 volts. This causes Q1 to works and buzzer emit loudly.

‘Keep reading: Temperature controlled on off relay circuit using LM393’ »

How to build this projects
We assemble all components on a universal PCB as Figure 2. Since it is fast and saving our money. Also, you can apply this to design a good PCB layout.

But this a little project, you can do it.


Figure 2—the components layout on the universal PCB.

The component lists
Resistors size ¼W +5%
R4—470 ohm
VR1—10K POT trimmers
VR2—1K POT trimmers.
VR3—100K POT trimmers.
The semiconductor
Buzzer 9V
Battery 9V with terminal
The universal PCB

‘Keep reading: Automatic Fan Controller circuit’ »

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This Post Has 4 Comments

  1. will this project on bread board

  2. It’s a pity that such a poor English makes this website almost useless

    1. Hello Garouda Hanouman,
      Thanks for your feedback. I will rewrite all article.
      I hope you come back to visit my site again.

  3. does TL071C(or TL081C,TL082C etc.) work under 273,3 degrees Kelvin? This information important an another circuit for me.

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