Smart Coffer Cup- Audio Reminds for Your Hot Coffee Temprature

    I like to drink coffee in office, it refreshes me  a better state in my working, especially in the winter afternoon. But I always have a problem: the coffee is too hot as i made it , so I have to continue working to wait for it, but when I remember my coffee again,  it usually gets too cold.
   So i want a simple device to monitor the temperature of my coffee and as the temperature belows my set value ,it reminds me: hey,  your coffee  is OK, you can drink it now!
    As a graduate student studying history, I am not good at electronic, i can not understand anything about hardware programming such as Arduino too,  but i believe,  it is simple, and interesting!
    I found some modules, plans to use a simple way to make such a device. The pictures above shows my thoughts of the solution.

    This system uses wireless charging module, so the cup modifications do not affect its normal usage .  After preparing your coffee, just place the cup on the special mat , as the coffee temperature became suitable for drinking, the buzzer will automatically reminds you drinking.
    I use the following modules:
1. Temperature Threshold-Setting Module;
2. Wireless Charger;
3. 5~12V DC power, it is very common used,  i believe there will be one in your home;
4. Buzzer & DC Jack;
5. Thermal Glue that you can get from any local convenience store;
6. Cup and Plastic Blocks;
Ok, with some tools such as knife  and scissor,  Let’s begin~

Step 1: Wireless Receiver+ Temperature Monitor

    I get this temperature monitor module from web, it uses a thermistor to detect the temperature and compared it with the threshold set by a potentiometer, as the temperature Higher&Lower than the threshold, the output varies between 0 and 1. As schematic_1 above.

     Althougth the circuit maybe easy for electronic students , it takes me 2 hours to understand. As the thermistor is NTC, so as the temperature higher than the set value set by the potentiometer, the LED will be ON, and will be OFF as the temperature lower than the set value.

     But it is not want i intended.  I need a buzzer shouting when the temperature is LOW and keep  Silent when temperature is HIGH. So , i make some modifications:
1. Solder off the LED
2. Add a buzzer between the output and Ground.
As schematic_2 above.

    And, in order to meet the current requirements of the buzzer, i modified the resistor between VCC and the output of the LM293 from 10K to 120 ohm.

    Then,  Connect the wireless receiver to the power circuit of the board. Connect the Red wire to  VCC and Black wire to GND.

Step 2: Wireless Charger Connection

    The wireless charger uses 5~12 DC power, connect the power wires to a DC jack . Notice the “+” and “-” pole of the DC jack, connect the Red wire to the “+” pole(the Outer one) , and the Black to the “-” pole(the inner one)

Step 3: Install the Wireless Receiver+ Temperature Monitor Onto the Cup

    First, mount the wireless power receiver on the bottom of the cup , a flat shape as it is, you can easily mount it  at the bottom of the cup. Then mount the temperature monitor board on the side wall of the cup, notice that make the temperature sensor close to the cup , so that it  can detect the internal temperature of the coffee. I uses some thermal glue to make the sensor detects the coffee temperature better. Although this is not accurate, but for my glass cup it was enough.

     If you uses a cup that has a  High-quality insulation , then I suggest that you use the new temperature sensor and put it to the inside of your cup so that it better monitor the coffer temperature,  wish that the sensor does not change your coffee taste.

    Finally, use a tape to fix the whole board to the glass wall. Note that do not cover the potentiometer, because we will need to  adjust this potentiometer to set  the “Reminding temperature” later.

Step 4: Prepare a Shell for the Wireless Charger

　　I uses a plastic black that are widely used in packaging to make the shell. Use a scissor to make it, note that do not make it too large or small, make it suitable for you cup.
　　Also use a scissor to make a “pocket” in the plastic block , and put the wireless charger into it.  Use a tape to to fix it.

Step 5: Adjust T the On-board Potentiometer to Set the “reminding Temperature”.

    The last step is adjusting the potentiometer to set the threshold temperature that begin to remind you drinking. Place the cup on the wireless charger mat, the red LED ”Power”on the board will be on to remind you that the wireless charger&receiver works well. 

    Pour some water that you think its temperature is ok for your drinking into the cup, and adjust the potentiometer to the threshold to make the buzzer just begin to shout/silent . So its further working, when the sensor detects the temperature of the liquid in the cup is higher than the set value , buzzer not ring; When the temperature starts below the set value, the buzzer will begin to
Reminds you the coffer is OK~

    If you think the buzzer too loud and affect you and your colleague, you can change the position of the cover on the buzzer to adjust the loudness.