78l05 Positive 5 volts regulator can provide 100 ma max , if you overload it with excessive load then ,inbuilt over load (thermal overload protection ) kicks in and lowers the current flowing through it
This lower side of 7805 can be used as temperature sensor.
Step 1: The Only Part Needed!
Step 2: Follow This Circuit
R1 and R2 are internal resistance you will only need external filtering and decoupling capacitors to do it effectively
input voltage should be higher than 5 volts ( you all know that )
Step 3: Is It Useful ?
but considering its simplicity (only 7805) and required parts you can do it right now !
Step 4: Watch How to Do It
Stay cool and watch the tutorial.