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  • Here are 2 heat sensor circuits, first one is build with the 4060 IC, the second one is simpler than the one before and has fewer components. It is an ideal add on circuit to monitor heat in CD players, Amplifiers etc. It senses heat from electronic devices and gives a warning alarm.

    Heat Sensor Schematic with the 4060 IC

    heat sensor with 4060 IC

    Heat Sensor Schematic with the transistor

    heat sensor with transistor

    The heat sensing element is the NTC Thermister and its resistance drops when the temperature increases. Resistance of Thermister is set by VR and if the temperature is below the preset level, transistor T1 will be out of conduction and keeps the buzzer and LED off. When the temperature near the Thermister increases, T1 conducts and buzzer beeps.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    12 Responses to "Heat Sensor Circuit"

    1. osama mohammed says: on December 10, 2010 at 3:58 am

      is the capacitor 0.22Farad?


    3. Sir good day.. Sir its functional if i will use a NTC 4.7k BIG in size and BLACK in color?In my place all enterprise only sell a big type thermistor that use for TV?

    4. This circuit DOES NOT WORK. Do not build it.

    5. I think

      1. The circuit may work but it will be very difficult to adjust the 10K pot to suit the change in resistance of the 4K7 NTC thermistor

      2. An active piezo-buzzer is connected directly to pin 5 of CD4060. Not a good practice!

    6. The CD 4060 is a DIGITAL CHIP. Pin 12 needs a DIGITAL SIGNAL to start and stop the chip. This involves a voltage from 0v to near rail voltage. How is a thermistor going to provide this voltage??????

      The chip will deliver 10mA. What piezo buzzer works on 10mA??????
      Just another circuit from D Mohankumar that does not work.

    7. Karthik Hebbar says: on June 26, 2015 at 9:58 am

      Tried it out and its working for me!@Colin Mitchell, Yes the IC is digital,but the thermistor need not provide rail voltage. it should just ground the pin 12 to reset it.
      A HXD 12v piezobuzzer is working for me.
      Kudos @D Mohankumar!!

    8. Colin Mitchell Colin Mitchell says: on June 26, 2015 at 10:23 am

      You don’t know what you are talking about.
      How is the thermistor going to provide a swing of about 66% rail voltage?
      Show me the part number of the piezo buzzer

    9. Colin Mitchell Colin Mitchell says: on June 26, 2015 at 10:30 am

      Corrections to above reply

      The thermistor will work with the CD4060.
      Show me the part number of the piezo buzzer

    10. Karthik Hebbar says: on June 26, 2015 at 4:51 pm

      The specs of HXD piezo buzzer I bought,

      Rated Voltage: 1.5~24VDC
      Operation Voltage: 1.3~28VDC
      Rated Current: ≤ 42mA
      Sound Output: ≥ 85DB
      Resonant Freq: 2300± 300HZ
      Operating Temp: -20º C~+45º C
      Storage Temp: -20º C~+60º C
      Weight: 2g

    11. Colin Mitchell Colin Mitchell says: on June 26, 2015 at 5:12 pm

      Don’t forget, the chip can only deliver about 10mA

    12. Karthik Hebbar says: on June 26, 2015 at 8:51 pm

      yes!! I have seen piezo buzzers operating at even 5mA as long as the voltage is sufficient.
      I have the working circuit with me now!!

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