Temperature measurement for clock

The reason why I added a thermometer to the clock was because I had an LM335 lying around, which I bought at a website that doesn't exist anymore. It was relatively easy to connect (as you can see from the schematic). The resistor is pretty lenient, as the whole system needs to be calibrated on the PIC microcontroller that is attached. Unfortunately this also means that the system is very sensitive to the voltage that is applied: I currently have 6V attached to the system, which is not enough to properly prime the 7805 I use for power (a minimum of 6.6V is needed) which means that attaching a higher voltage source (like a 9V adapter) causes the temperature display to behave erratically. This can, of course, be easily avoided by just having enough power. Still, it is likely that for each different 7805 it has to be adjusted separately. This can be done externally by hooking up a 10K potentiometer to the ADJ pin of the LM335, however, since this was a one-off implementation I decided to just leave it the way it is.