Last month Paul shared his Raspberry Pi based Temperature Monitor which he had prototyped on a breadboard. Now he has taken it to the next level using the KiKad PCB Design tool to layout a board. The documenting of his design decisions is what makes this build interesting.
He wanted to use OSH Park which charges by the square inch. After finding out that 3 boards would cost him $26 he was determined to get his board cost down. Pushing the components together and shrinking the board a little helped but not by much. Swapping out the unnecessary 8 channel ADC for a 4 channel ADC freed up a little more room. However, Paul still was not happy with the cost. So he swapped most of the through-hole parts out with surface mount components and after a good nights sleep changed the design yet again using modern temperature sensors. After all this his total cost was $2.90 cents for 3 boards.
It just goes to show that a few hours of planning can keep your wallet fat. See all the details here.