This was a personal request from my boss to his bike, he notice that an empty space in the dash and ask me to see if I could add an temperature and voltmeter indicator, as I check the space I realize it was the size off an standard 2x16 Alphanumeric lcd and it could be easily fit. In the first approach I used an themistor and found out it was a bit unstable and not very accurate, for my second attempt i wanted a chip solution and the easy way was the DS1721. After having all components selected I draw the schematic and pcb, and it is simple circuit based on a pic16f819, the working principle is very basic for measuring the temperature it reads the data via i2c bus and for the voltage it reads an analog input connected to a voltage divisor
After assemble the circuit, I started the software and realize that the 5v form the regulator were good for analog reference and didn't assemble the TL431, all was working fine until the connection off the lcd backligth, I hadn't consider the current consumption and as result the magic smoke from the regulator and transistor, to solve this I had to connect a dedicated regulator for the backligth.
