## Temperature Meter

Various temperature based project is already published in www.electronicsproject.org. Now here is very simple project “Temperature Meter” build from very few components and can be understand even by beginners. The project temperature meter indicate three stages of temperature i.e. hot, warm and cold.

### Circuit description

The entire circuit of temperature meter is build around window discriminator IC TCA965 followed by thermistor and few another components. Thermistor is a special type of resistor whose resistance varies according to change in temperature. Thermistor TH1 is used here as temperature sensor. Resistor R1 with thermistor TH1 is used as potential divider and the value of resistor R1 is so chosen that voltage at junction is half. Variable resistor VR1 with VR2 is used to control the level of temperature indicated by LEDs. The three different LEDs is connected to the output pin 14, 13 and 2 through resistor R3, R4 and R5 respectively in order to indicate the status of temperature. LED1, LED2, LED3 indicate hot, warm, and cold respectively.

### PARTS LIST

#### Resistors (all ¼-watt, ± 5% Carbon)

R1 = 47 KΩ

R2 = 100 KΩ

R3 ,R4, R5 = 4.7 KΩ

VR1, VR2 = 10 KΩ (linear pot.)

#### Capacitors

C1 = 10 µF/16V (electrolytic)

IC1 = TCA965

LED1 = Red

LED2 = Yellow

LED3 = Green

#### Miscellaneous

SW1 = On/Off Switch

## 5 thoughts on “Temperature Meter”

1. a says:

I didnt find the value of R4 can you please give it?

1. R3 , R4 , R5 all 4.7 kOhms or according to the size and current limit of the LED you are using.

1. vikashojha says:

I didnt find the IC Tca 965 in nagpur?

1. The IC TCA 965 is a simple window discriminator IC which compares the input voltage to a defined voltage window (Through VR1 and VR2) and gives digital output.

Please look into datasheet to find similar or replacement IC.

I am not sure about it’s availability in your city.

But you might be able to find the exact or replacament IC through the US supplier here: http://bit.ly/Y8L1Ue

2. nibir nibir says:

please tell me alternative IC for TCA965.