1. First of all, you should know that, ESP-01 has only 2 GPIO pins and no ADC pins. So we can only use digital output sensors.
2. LM35 (Temperature Sensor), LDR (Light sensor), Pulse sensor etc are all analog sensor. They require ADC pins, which is not easily accessible in ESP-01.
3. Also note that DHT-11 (Temperature and Humidity sensor) is a digital sensor. So we can use, it to measure temperature.
4. Some other digital sensors I found are: HC-SR04 (Ultrasonic Distance sensor), HC-SR501 (PIR Motion Sensor) etc.
5. In-order to use Analog sensor, you should buy higher version of ESP-01 (Eg: ESP-12F)
6. When referring to the ESP ADC pin you will often hear these different terms interchangeably:
ADC (Analog-to-digital Converter)
Analog Pin 0
All these terms refer to the same pin in the ESP8266.
6. In ESP-01, you can access the ADC, by making a precision soldering. Read this article.
7. ESP chips have been developing at a great pace.
These tips/notes may be of use to somebody, who is getting their hands dirty in IOT.
PS: I come from a computer science background. So if you find any mistakes or want to add additional content to this article, please feel free to post a comment.
Have a nice day 😉 .