Multifunction Digital Thermometer

Step 2 Start Building

For this step, use the attached schematic (word or AutoCAD) to build the circuit. I always find it helpful to first build it on a solderless breadboard. This makes it easy to fix any problems that arise before you want to pull your hair out :)

Before you start soldering it is probably best to first cut the breadboard to the final size and arrange all of the larger parts on the board (as seen in the 2nd image below). Don't forget to allow room for the buttons above the board and a power button off to the side.

It should be noted that in the schematic that R5 is a comparison resistor for the thermistor, and it might be included in your thermistor, so you should check your data sheet for how to implement your specific thermistor.

Comments

[007chrisac6]

Can i get an exact parts list? Im buying from Sparkfun. For example, I wanted to know the exact thermistor i need. Is it a10k thermistor or a LM series temperature sensor?

[gunterhausfrau]

another noob question. The comparison resistor, if I have a 10k thermistor would that imply at 10k comparison resistor? I have the datasheet, but I guess I'm being dim. Thanks for the information.

[J_Hodgie]

If the thermistor is 10k at room temp, then yes. You want to choose the comparison resistor so that it roughly equals the average of the varying resistor (it creates a 'voltage divider', if you want to look up how it works). This is because the voltage at the measurement point is in the middle of the measurement range, allowing the most sensitivity.

[klim142002]

Out of curiosity, what is the range on your variable resistor? I don't have that equilizer and I have some pots laying around.

[J_Hodgie]

It ranges from 1 kOhm to 11 MOhm