Dodge temp sensor

[longpole001]

not heard of this with the IN4148 method , how close to the temp source would the diode need to be , get any real temp variation ?

[mark_s]

not heard of this with the IN4148 method , how close to the temp source would the diode need to be , get any real temp variation ?

Just like any thermometer or sensor. It will measure the ambient temperature. If you wanted to monitor a power transistor it would have to make contact or be very close. Best way to see it in action is solder a 4.7k in series with a 1N4148, 1N914 or a 1N4001 connect it to 5 volts and measure the voltage across the diode. You can see the voltage change by pinching the diode or take a fan cool it down. The draw back to the diode method, is the voltage change is not linear. It was common to use a look up table to correct the non linearity. I don't remember how it was calculated, should be easy to find?

[Art]

It sound like a good approach.. I haven’t heard of it.
I don’t mind using a lookup table of three bytes
Basically I only want a rough range: Cool, Warm, Hot.
So I would only need a few constant values to compare.