How does your Thermostat work?
Hey friends, Happy Christmas and advanced New Year wishes!
Hope you were able to take a break and relax.
Let’s look at how thermostats work in your house this week. It’s winter time and I’m guessing there is a thermostat running in most of your homes. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for food, etc. Let's jump in!
How it works: 15-second answer
A thermostat uses a thermistor sensor to measure the temperature. As room temperature changes, the thermistor's resistance shifts, allowing the microcontroller to correlate it with pre-calibrated temperature values. If the room is too cold, the heater activates; if it's too hot, the air conditioner turns on. The thermostat functions as a straightforward on-off switch.
How do digital thermometers work?
We’re discussing the most commonly used digital thermostats. It heats or cools the room if the desired set temperature is higher or lower than the room temperature, respectively.
Misconception: There is more heat provided in a given time if the room temperature has to go from 15C to 40C as opposed to going from 15C to 25C.
This is wrong! We get the same amount of heat in a given minute from the heater. The heater just runs longer to push the room temperature from 15C to 40C than it takes to go to 25C. That’s all. So there is no complex controller logic behind how the thermostat works. It’s a simple on-off switch.
On the inside:
This is how it looks on the inside. If it looks scary to you as it did to me, all you need to know is that the highlighted component on the right in Figure 1 is a thermistor. It’s a sensor that detects the temperature of your room.
Figure 1: Thermistor inside a thermostat (TOP); Thermistor zoomed in (DOWN)
The thermistor’s resistance increases if the temperature is lower and decreases if the temperature increases as seen in Figure 2. The thermostat finds the room temperature by correlating the resistance value to the thermistor's temperature which is pre-calibrated and loaded onto the microcontroller board.
Figure 2: Thermistor’s resistance changing with temperature in a thermostat. The exact numerical values can change from one to another.
You can set the desired temperature using the control panel display.
Now, if the thermostat detects that the room temperature is lower than the temperature we set on the panel, the control board sends a command to turn on the heater to heat the room. If the room is hotter than we want it to be, a command to turn on the air conditioner is sent. This is how a thermostat works!
Fun fact: The term 'thermistor' is derived from the term THERMally sensitive ResISTOR.
Question of the week
We’re using a thermistor whose resistance increases if the temperature decreases. This is called an NTC thermistor. Why are we not using a thermistor whose resistance increases if the temperature also increases? The latter is called a PTC thermistor.
Receive cool a gift for the new year if you answer the question correctly by replying to this email 🙂
Gadget of the week
Figure 3: Ray-Ban Meta Smart Glasses
Ray-Ban Meta Smart Glasses: These glasses have a 12MP camera, open-ear audio, and live streaming capabilities for Instagram and Facebook. It has an advanced conversational assistant that you can engage with by using “Hey Meta”. Also, you can share the photos with your friends using the “Send a photo” voice command.
Thank you for reading!
Have an amazing rest of the week, and take care!
Until next to next Wednesday,
Chendur
