Temperature Sensor

257

02:30:57

As the temperature rises, the transistor’s beta rises resulting in a fall in voltage. Likewise, when the temperature drops, the transistor’s beta drops as well causing the voltage to rise. The voltage rises/drops by about 220-230mV per 10A/A change in beta.

published 7 years ago

hurz

7 years ago

If you connect the base resistor to the top rail and not at collector you get a better result, cuz from collector you get negative feedback. Increase of temp will decrease collector voltage and does reduce the base current. Then keep an eye on power dissipation, at 9V with 1kOhm the transistor burns 20mW worst case, so better reduce supply voltage to decrease current collector. So its less self heating. http://everycircuit.com/circuit/6016819881312256

jason9

7 years ago

I thought about that, but thought that it would be too beta sensitive, but I suppose that that’s actually the whole point of the circuit. I’ll make the change now.

hurz

7 years ago

Beta sensitivity is what converts temperatur into collector current. With negative feedback you supress this effect you do want. 👍

fancycontrollers

7 years ago

Way to go hurz 👍

hurz

7 years ago

Fancynacy, I dont think jason9 likes your spam on his circuit, so please stop that and try to do your first working circuit instead.

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