Making My First Digital Thermometer for Less Than $30

[amielaroux]

amielaroux submitted a new Showcase Item:

Making My First Digital Thermometer for Less Than $30

So the summer holidays are here, and I am not the kind of person to just lay around and do nothing so I thought I would share with you all my first project called:

"Making My First Digital Thermometer for Less Than $30"

Ok so doing a quick Google search they are pretty cheap, but from what you will get out of it will be the sweet taste of satisfaction of creating something.

These directions will show you how to make a simple digital thermometer for less than $30 using a few electronics and three (3) ICs.
Digital Thermometer could be used:

• It can be used for measuring child’s food temperature.
• It can be used for measuring temperature in laboratory experiments.
• You can use it in measuring body temperature.

The following are the parts required:

• ICs: CA3162, CA3161 & LM35.
• 10k resistor(potentiometer)
• 50k resistor (potentiometer)
• 0.27µF capacitor
• 2N3906 transistor
• 2N3906 transistor
• 2N3906 transistor
• Seven segment LED display - I liked to buy mine online as there were a wider range of choice

Places to buy this stuff from:

Newark - http://www.newark.com/
Premier Farnell element 14 - http://uk.farnell.com/

I found that a lot of these tools were also available at home too, so the price would probably be a lot cheaper in the end.

Tools that you will need:

• Soldering iron - http://www.homebase.co.uk/webapp/wc...ay?langId=110&storeId=10151&partNumber=337237
• Solder
• Side cutters (you can use anything to cut the remaining capacitor and resistors legs)
• Solder sucker (to remove excess solder in case of a mistake )
• Screwdriver (for adjusting the potentiometers)
• DIL sockets

Step 2: The Circuit

Circuit diagram

View attachment 16824​

Mount ICs: CA3162, CA3161 and LM35 on DIL socket and connect the other components in their right positions. You can etch your own PCB or build it on a breadboard using connecting wires. Everything in the circuit diagram is in their exact positions, so you can build it into a circuit board straight away.

Step 3: Soldering the components


This is a straight forward step of soldering the components together. Start with the resistors and the capacitor, then the transistors followed power terminals and potentiometers then the IC and seven segment LEDs display last. Keep in mind to use DIL sockets to mount the actual IC, and if you don't use DIL...

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