temperature indicator

59 temperature indicator 1N414£ 547B The temperature indication of a heat sink on a power transistor in high power circuits can be extremely useful. A simple, inexpensive tem- perature indicator would be ideal for this purpose since accuracy is not an important factor. R1= In the design for the temperature D1 indicator here, the voltage drop across a diode that is held at ambient temperature is used as a reference level. The temperature detection is carried out by a transistor mounted on the heat sink and/or close to the power transistor in question. In the circuit diagram the temperature (or even in, if drilling the heatsink is acceptable) the heatsink as near the heat dissipating element as is practical. It must be remembered however that the maximum expected temperature should not exceed 125°C if you value your transistor. The current consumption of the temperature indicator will be little more than the LED current, about 20 mA, and then only when things are starting to cook!...