Coffee Temperature Indicator Circuit

Ever burnt your tongue because of coffee too hot?

This Coffee Temperature Indicator Circuit show how to make small circuit and which tells how hot coffee is!

It uses sensor to check temperature and then LED light up to say if coffee is good to drink or not.

So now we can enjoy coffee always at perfect hot.

Circuit Working:

Parts List:

Why measure coffee temperature?

Coffee taste depend on two big things how strong it is and how hot it is.

Finding right strength is easy but right temperature is little hard.

Most people like coffee hot to around 80°C.

This small circuit help stop people from burning their tongue.

Not everyone have got thermometer in mouth!

This coffee circuit use 2 LEDs, one comparator, one sensor which changes heat to voltage and one voltage controller.

How it work:

If coffee is not hot enough then circuit say 0 and transistor T1 no gives power.

Then T2 turn ON and red LED blink that means coffee is too cold.

But when coffee gets hot enough then green LED blink and that means coffee is ready to drink!

IC2 chip measure temperature and changes it into voltage.

To do this chip goes inside coffee or in small box like a probe.

For every 1°C rise voltage goes up 10 mV.

So for 80°C voltage is 800 mV.

We have used P1 a small knob to set this 800 mV on IC3 chip.

When IC3 gets 800 mV on plus side then it sends logic 1 and T1 turn ON.

T2 now turns OFF and red LED stops and green LED turns ON.

This mean coffee is now perfect hot and tasty!

Formula and Calculations:

LM35 is a small sensor chip which gives voltage that match with how hot it is in Celsius.

How LM35 work:

It make voltage goes up when temperature goes up and is very simple!

This is the rule:

Temp in Celsius (TC) = Vout / 10

where:

TC is temperature in Celsius

Vout is voltage from LM35 in millivolts, mV

Example:

If LM35 give 500 mV then:

TC = 500 / 10 = 50°C

So temperature is 50 degree Celsius.

This way we can know how hot coffee or anything is using LM35 sensor!

How to Build:

To build a Coffee Temperature Indicator Circuit follow the below steps for connections and assembling:

• IC3 741 op-amp should connect to LM35 temperature sensor IC2.
• To know which pin goes where check datasheet of these parts.
• Use voltage regulator 78L05 to give circuit steady power.
• Connect LM35 like this negative pin to ground and positive pin to power
• To set temperature level for comparison connect potentiometer P1 to IC3 741.
• LM35 sensor IC2 must go to 741 op-amp IC3.
• Also use proper resistors and capacitors to make signal clean and better.
• Connect red and green LEDs to show coffee temperature.
• Use T1 and T2 transistors to turn LEDs ON of OFF based on output from comparator IC3.
• Build the full circuit on a breadboard and follow circuit diagram carefully.
• Check all wires and connections and ensure there are no short circuit or loose wire.
• To test temperature put LM35 sensor inside coffee.
• If not possible put it in something safe like empty pen case and be sure it is dry.
• Turn circuit ON and watch the LEDs like red LED ON means coffee is not hot enough and green LED ON means coffee is perfect hot for drinking.

Note:

• This is just basic guide and actual design may change based on which parts we are using
• Always check datasheets of components and connect properly.
• If anyone is new to electronics then it is good to ask someone who know better for help.

Conclusion:

With this Coffee Temperature Indicator Circuit there is no need to taste and test our coffee every time.

It helps know when coffee is ready so we get best flavor each time.

References:

LM35