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Most coffee cup warmer projects on the internet are usually very hackish in design and don't put out enough heat to keep your coffee cup warm above anything higher than 30C.

Please do not be discouraged by the photos, I don't usually care about aesthetics of things that work. :)

In this Instructable you will learn how to build the next better thing. Mine keeps my cup warm at about 80C.

Things you will need:

  • Kanthal A1 26AWG resistance wire (you can obtain it on Amazon, just make sure it's 26AWG)
  • 2 heat resistant glass plates, or anything else that will not melt, break or conduct electricity
  • 9V power supply that is capable of providing 2 amps of power
  • Duct tape
  • Electrical tape
  • Wire cutters?

KEEP IN MIND: THIS CANNOT BE POWERED FROM USB, UNLESS YOU FEEL LIKE SCREWING UP YOUR USB PORTS AND VERY POSSIBLY YOUR COMPUTER IN THE PROCESS. YOU HAVE BEEN WARNED!

Step 1: Making the Heating Element

Cut a piece of resistance wire that is exactly 48 cm (1.57 ft) long. Mold it the same way as shown in the photo. Do make sure however that the leads are on the side and are at least 6 cm (2.36") long.

We're shooting for a 5.4 ohm heating element, which gives us exactly 15W of power at 9V, and since it's pulling 1.67 amps - we need a supply capable of 2A (to be on the safe side).

Step 2: Connecting the Coil to the Power Supply

Strip insulation off of positive and negative lead coming out of your power supply. Twist the positive and negative wires onto either of element's leads. Polarity does not matter in this case. Now cut a piece of electrical tape and insulate each connection well.

Step 3: Put It All Together

Sandwich the heating element between the 2 plates, and make sure negative and positive leads are not touching each other (don't worry if the element is touching anywhere in between EXCEPT for the final leads). Now secure both plates together with duct tape so they don't fall off - you're done!

<p>Really cool idea! Thanks for sharing! </p>
<p>Thank you! It is worth noting that all the coffee cup warmer projects out there are not capable of more than 300 mA of power output, which at 5V is in the puny mW range. :P</p>

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