I drew the schematic of DHT11 sensor by my own understanding, and I wrote a statement explaining how DHT11 works internally. I'm not sure if they are 100% accurate. I hope I can get corrected if anything I state is not correct or accurate.
How DHT11 works: The 5V goes through VCC, data, to the INPUT pin, which is where it sends to data through the MCU(microcontroller) to a computer so that the computer can read the temperature and humidity. There is a 10K resistor between the path of data to pin and VCC, which can pull the current up to VCC so it can read HIGH, There should be a transistor switch between DATA and GND(I just drew the most common switch sign for simplicity), which can pull the current down to the GND so it can read LOW.
The transistor switch is generally opened, not connected to the GND, so it reads HIGH when it's idle. When it needs to start sending data, it gives a"knock"first. It closes the transistor for around 50 μs, which tells the microcontroller it's gonna start sending data. After this, it opens the transistor switch for a short time(reads HIGH for ~28μs) to send 0, opens for a long time(reads HIGH for ~70μs) to send 1. It does this 40 times very fast in 0.04s, to get 8 bits of temperture, 8 bits of humidity, and some checksum so the MCU knows it is correct. Finally it gets the temperture and humidity.
I think the video is wrong about the moisture sensor part.
These white ceramic squares are commonly known as dew sensors (HDS10 element).
They are some sort of polymer that changes (increases) resistance with humidity.
Not capacitive as the author states.
Dew sensors were commonly used in VCR's, where the slightest moisture on the fast rotating video head drum could result in a bunch of tape-salad.
Leo..
Interesting.
You would think that moisture would reduce the resistance.
Some plastics (polymers) absorb moisture. Nylon is an example.
I was surprised to find on a spool of strimmer nylon cutting cord, the advice to soak it in water before using it, to reduce breakages.
Either way, clever materials.
Yes I do remember the VCR moisture problems.
Most of your explanation is wrong.
How it actually works is explained in the datasheet.
Yes! Everything is in the datasheets, but we still have the forum to help those who find it difficult to interpret the information in datasheets, which are often cryptic.
Many moons ago I published an article for a bathroom fan sensor in Elektuur (Elector) magazine. I had to investgate these sensors in depth for that.
This was well before the time that more modern sensors and small microprocessors were available.
I would only use the basic DHT11/22 for learning. There are much better ones out there.
Leo..