1A-Basic Circuit-Coffee Cooler

By zacmau / September 10, 2014 / Graded Projects / No Comments

Group Members: Sara Johnson, Ashley Lai, Zac Mau
Roles: Sara Johnson as tutor/scribe, Zac Mau as designer/scribe, Ashley Lai as integrator

Introduction

While coffee is brewed near boiling temperatures, the optimal temperature to enjoy a hot drink is 70℃. At this lowered heat, your taste bud can register the full range of flavor profiles and avoid dangerous burns.

To allow premium brewing while avoiding a long wait for your caffeine, we have created the Coffee Cooler. A paper coffee cup is inserted into the cup compartment with the lid removed, and if a temperature above 70℃ is registered, the mounted fan turns on, cooling the drink.

We have create a one-in-one-out system that is activated by the liquid’s temperature and outputs physical air circulation from the fan. The heat is registered by a thermistor, which electrically triggers a magnetized coil by increasing current flow. The switch allows an external battery to power the fan and cool the drink to the desired temperature.

Technical Notes

The temperature of the water is measured by at 10K thermistor through the coffee cup, which accurately transmits the drinker’s temperature because of the paper’s low specific heat capacity. Upon contact with the hot drink, the thermistor decreases in resistance of the thermistor decreases its resistance linearly byR = -kTbecause of its negative temperature coefficient . Reducing the resistance increases the current flow to a 5V relay, magnetizing the control coil and physically moving the relay’s internal switch. The switch completes the second circuit, allowing a 3.7V LiPO battery to power a brushless 40mm fan.

PIECES

tactile on-off switch

5V relay HASCO KLT1C6DC5

10K thermister

9V batteries

3.7V LiPO 1600mAh

dc brushless fan FFB0412SHN

ideal for cooling:

5-7v: solid wind, audible

need at least 4.2 volts

3v – turns off

specs: