ECE 110/120 Honors Lab Section : Heating Coaster for Drinks

Final Report

Heatplate.png

Raimi Shah

Kunjie Zhao

Our project is going to be a coaster for a drink like tea or coffee that will be automatically controlled such that you can set a temperature for the drink to warm up to. We will accomplish this by using resistors that have very high resistance that will be embedded in a conducting coaster. To make sure that the temperature is correct, we will embed a temperature sensor in the cup which will monitor the temperature and increase or decrease the heat as needed.

Feb 15, 2016:

Finished high-level design.

Heatplate (1).png

Feb 22,2016

Put some orders in for various parts. changed the  design slightly to use a heating pad  instead of creating our own heat through a bunch of resistors.  We also placed an order for a temperature sensor that outputs a voltage. we think that this will be useful so that we can control the power supply to the heating pad. From this, we can make the pad a consistent temperature, and hopefully, ensure that it does not burn out or get too hot.

Feb 29, 2016

This week, we were waiting on the parts to come in. In the meantime, we discussed more about specifics of the project. First off, we decided to order a wall power supply to input to our logic so that we can control the power supply when the temperature is too hot or too cold. Also, since the temperature sensor will send an output voltage, we need to connect this to a microcontroller unit so that we can decide if the heating pad should continue to get power. We would also like to implement an LED to show when the heating pad is actually receiving power, and another LED to show when the drink is heated to completion. Made a FSM for the logic.

Mar. 7 , 2016

Finite State Diagram.png

This week, we got our parts and started to try to build the circuit. To do this, we got a LM339 comparator in order to check if the output voltage from the temperature sensor. We checked out the datasheet of the comparator and the temperature sensor to see where the input/output would connect, and we wired the circuit accordingly. Right now, we have the temperature sensor connected to the comparator chip, and we need to make some logic that will help implement our design. Then we tested the heating pad to see how hot it gets (which is not very hot). We may need to change the goal of this project or redesign a bit or get a heating source that can supply more power, thus heat up faster. We are not totally sure how the design logic will work, but we will need to use gates to control input to heating pad.

March 14,

We had quite a few problems this week, we weren't sure what do with the output of the comparator. We knew that the comparator outputs a 1 or a 0, but we werent sure how to make the circuit that allows the heating pad to be heated. Then we learned that it would be very hard to convert digital to analog and then build a circuit off of that. So now we are deciding to use a BJT, relay, or an arduino. Also we learned that we need to extend the temperature sensor, so we will have to sauter it so that we can put it closer to the liquid temperature. We found out that we will have to test the output voltage of the temperature sensor in order to make a reference voltage to be compared. We  were waiting on the power source again so we could not find this reference voltage, but we know how we will create it. Once we find the voltage from the temperature sensor, we can use resistors and a battery to make a reference voltage that we can compare. We will need 2 batteries for this because we need to power the reference and also the heating component.

March  28,

We decided to use Arduino to control input current to the heating elements depends on the voltage that the temperature is outputting. Unfortunately, we are not able to receive our power adapter today, we can not further test our circuit boards and calibrate the voltage output by temperature sensor to a correct temperature scale. We then research into how to program our Arduino so we can directly detect the voltage that the sensor is outputting. through this, we dont have to use the comparator chip to compare the voltages and do the hassle to convert the digital signal to analog.

April 11,

This week we tested our circuit and saw that we were not getting enough current to the heating pad from the arduino. So to fix this, we are trying to use a bjt that can amplify the current that goes to the heating pad. When we set up this circuit, we needed another power source like Vcc from the circuits that we see in class. We calculated how much resistance is needed to get the heating pad 600 mA. This is 475 ohms so we used a 470 ohm resistor. When we hooked up the voltage generator to the circuit, it burned through one of the wires going to ground. We are going  to correct this next time. We think that we have the correct code for the arduino that follows our  finite state machine.  

April 17,18, 

We have created the circuit and it works properly. We are currently using the 5V power source to power our heat plate. The code is finished and we soldered the temperature sensor so that we can connect it to a cup of water. Since we are not getting much current, we will probably need a small paper cup of water to test with, so that it can actually heat it up. We still may need to calibrate the sensor for the arduino. We plan to get a very small cup wit a little bit of water so that we can heat it up and have the temperature sensor control the heating pad. We used the transistor that was in the lab kit beacuse the one that we were using was not getting current and we couldnt look at the datasheet.

April 24,25

This week we finished our project. We connected the circuit to the heating pad and soldered the the temperature sensor so that it could be longer and fit inside the heating pad so that we could get better temperature readings. The problem with our project is that the heating pad does not get hot enough to heat a liquid. But everything works as intended and would work as intended with a better heat source. We also added a red LED to indicate that the heat is on, and a blue LED to indicate that the heat is off.