Hello. I have finally found some time to design my own smart thermometer to measure temperature and humidity.
I am overwhelmed about the different options available in the market. Some of the most popular options:

1. AHT20
2. BME280
3. DHT22
4. DHT11
5. HDC1080
6. SHTC3
7. SHT21

and hundreds more!

Please share your knowledge and experience with me about different sensors that you have worked with and help decide which one to choose

 

You need to list your specifications: Working ranges, precision and accuracy. In general you'll pay more for more of all three of those. Waterproof? Some of the many devices may not meet your specs, so the list gets shorter.

Then there are likely other factors related to your planned design and build, things such as supply voltage, communication methods, sensor distance from circuit board, size and footprint, and lots of others.

There are plenty of commercially available devices for getting temperature and humidity. Maybe your reasons for making a DIY version would help narrow the field. Worth thinking about.

 

There is no "best" temperature/humidity sensor. A lot depends on your requirements and your level of expertise.
I would like to suggest a Senirion SHT40 sold by Adafruit.

https://www.adafruit.com/product/4885

 

You need to list your specifications: Working ranges, precision and accuracy. In general you'll pay more for more of all three of those. Waterproof? Some of the many devices may not meet your specs, so the list gets shorter.

Then there are likely other factors related to your planned design and build, things such as supply voltage, communication methods, sensor distance from circuit board, size and footprint, and lots of others.

There are plenty of commercially available devices for getting temperature and humidity. Maybe your reasons for making a DIY version would help narrow the field. Worth thinking about.

Apologies for not listing all those points in my initial post. I will explain the specifications briefly:

Working range - Just a standard temperature working range. I want to be able to measure the coldest winter temperatures (down to -30 °C and hottest summer temperatures up to +40°C.

Accuracy - Ideally as accurate as possible. I'm hoping < 0.5° and < 3% Humidity.
Some sensors such as DHT22 in the datasheet say that the sensor is capable of measuring temperature within 0.5°C accuracy but from different forum posts online I read that this is very far from truth. It is more like +- 2° error

Budget - Up to 50$ for a whole PCB (Since I will be designing my own custom board and also a mechanical case for a device)

Waterproof - Ideally should withstand a light rain ( Lets say I bring my device outdoors to measure temperature and its raining lightly ).

Other factors such as dimensions, voltage, communication - Since I am designing my own custom board, I have a lot flexibility so I do not mind. Ideally, I would like the temperature/humidity sensor to be flush with the mechanical case (I will 3D print it). Some IC's such as HDC1080 are so tiny that is hard for me to imagine how is it going to look like inside a mechanical case since I assume the chip itself must be exposed.

Reason for doing this project - I am aware that I can buy a device that will measure temperature and humidity. But the point of this project is to learn more about hardware/mechanical design as well as programming.

 

There is no "best" temperature/humidity sensor. A lot depends on your requirements and your level of expertise.
I would like to suggest a Senirion SHT40 sold by Adafruit.

https://www.adafruit.com/product/4885

I appreciate the fact that this sensor is very small form factor (My overall device design can be very small with this one). However, I cannot imagine how can I design a PCB and a mechanical design that would be suitable for this type of sensor.
Since the sensor must be exposed to the outside (cannot be enclosed inside a mechanical design). Do I just cut a tiny hole in my mechanical case to ensure fresh air from outside can get in? Would it look something like that?


Is there any way to improve the water resistance to the sensor? Can I cover it with some lacquer or some other chemical without decreasing its ability to measure ? What would happen if I bring it outside and a rain droplet got in the hole