Temperature measurement using diode 1N4148

Here is temperature measurement using diode 1N4148 and LM741 easy to make and use. Out to Voltmeter. Low cost too !

When I wants the circuit takes the temperature to are simple. I uses Diode 1N4148 be formed check the temperature. By when feed voltage change it. It is have current flow be stable. When the temperature that Diode, change make Voltage. At it modifies with VR1 and VR2 fine decorate for show that is correct most fining decorates. The important I uses the temperature certainly compare with accurate temple. By compare with reserve 0 the degree Celsius per 0 Volt. For the certainty advises that, should use Digital Voltage Meter. Show well almost forget the important point should. Give power supply Regulator high-quality , such as IC 7815 and IC 7915 etc. Try usable this circuit sees, regard good base of the circuit takes the temperature sir.


Note: In addition to this circuit You can see below circuit  : The dfferential Temperature Relay Switch or Balance temperature switch. They uses both diode 1N4148 as sensor heat or temperature as well. and using IC-op-amp -741 too.

The dfferential Temperature Relay Switch or Balance temperature switch

This is Circuit Dfferential Temperature Relay Switch .
Use IC 741 for control relay ad Diode D1,D2 for sencer Temperature . VR1 for adjusable voltage.
How it works
Usually we have seen in this type of equipment, consisting of thermistor or temperature sensor in variations. Around this time, found sensor which will that is new it that new, will be old it is old, Actually, because is known, and then some, I will explain it to someone who knows only
Temperature sensor with a semiconductor devices.
-It is actually, all the semiconductor resistance within. Which decreased when heated, will be very or least it is up to the agents used in the doping process. This includes a semiconductor, resistor, integrated circuit, transistor, etc..
-A diode is a semiconductor device at inexpensive, as compared to other devices, then select is temperature sensor in this circuit.

Dfferential temperature Relay switch using IC-741

As show in this figure below, we set to have a very high gain with the op-amp IC open loop style. Using changing of signal is little at input. To bias the transistor Q1 to drive a small relay. And will bring contacts of the relay, to turn – turn the external device another. May have to turn off the relay coil is connected with heat. Or to go off – open the solenoid.
Tuning of the circuit.
– In the process tuning diode must be placed close to the body with the same temperature. Adjust VR1 to close most the points of balanced circuit. By the op-amp is not working.
– Then test it by putting fingers catch diode D1, Voltage drop across D1 is reduced, makes voltage at pin 3 is over. Relay will working.
– If in case you want to really use. On coil thermal diode D1 is controlled, the higher the heat is cut off from the circuit. Make the temperature, in that case do not add up. (Be reduced gradually) Wait until the heating coil and a diode D2 At control the temperature exceeds at set of diodes D1 control.
Experience can not control the heat to maintain At temperature at a given. Just makes temperature of the coil valuable very similar. Which preset temperature may be increased indefinitely. Up to the maximum coil temperature heat can produce up. And also mechanic used through the high the current, makes shorter the lifespan.


  1. Arend September 6, 2014
  2. chayapon September 6, 2014

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