Ok the object is to display the temp in C & F on a 3 digit 7 segment display using the following.
Arduino Uno
Ds18b20 - digital One wire temp sensor
(2) 74HC_HCT595 - shift register
1k resistor network (shown under the LED)
3 digit 7 segment common cathode LED display
SPST NO MC switch
A few other odds & ends (see pic)
Total noob here so all input or better ways to do this is welcome!
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Hi Meden,
Unless you are using your other Arduino pins for something else, you definately don't need the shift register to drive the transistors. A 270R resistor from base to three output pins on the Arduin will work just fine.
You don't need the other shift register either, unless your LEDs are high current, you can just use eight outputs from the Arduino through the series resistors, as long as you are not taking more than 40mA per segment.
For example software for driving 4 digits in this way, download the sketches from http://www.arduinoevilgenius.com and look at project 30.
Hi,
10 butons - 7 pins (buttons in 4 x 3 array - there is an Arduino library for key matrix)
Actuator and servo - 2 pins
LED segments - 8 pins
LED common transistors - 3 pins
Makes 20 pins 
Only 18 available on the Arduino - you can use the Analog Ins as outputs too.
So maybe keep the shift register for the segments.
The more hardware, the more chance of something failing. Once the software is right, it stays right!
