A 20-Sensor Starter Kit for Arduino/Raspberry Pi

Check on Amazon I received one of these.

Sensors are cheap individually, but buying them one by one means shipping costs or transport end up costing more than the parts themselves.

This kit packs 20 different sensors in DIP format, ready for use with Arduino or Raspberry Pi.

Whether anyone actually uses all 20 is another question — and some of them I couldn't even identify, so I looked up every single one.

Actually, the manufacturer's site has detailed explanations for all of them. In English.
http://osoyoo.com/?p=403

Hall Effect Sensor Module

A magnetic field sensor. In English it's called a "Hall Magnetic Field Sensor."
Sounds pretty cool. A bit sci-fi.

Rather than measuring magnetic field strength, it outputs a simple digital HIGH/LOW result.

Pins left to right (the − side): GND, VCC+5V, Digital Input PIN.

DS18B20 Temperature Sensor

At first glance it's impossible to tell this apart from the Hall effect sensor, but they're completely different.

This is a programmable 1-Wire sensor. When using it with Arduino, load the OneWire library:
OneWire Library

Write 0x44 over 1-Wire to trigger a temperature measurement, then read back the result with 0xBE.
See the DS18B20 datasheet for details.

Pins left to right (the − side): GND, VCC+5V, Digital Input PIN.

Good practice for getting familiar with 1-Wire. And speaking of 1-Wire, there's a well-known 3D printer brand that uses it to protect their cartridges... but that's a topic for another day.

3-Color Full-Color SMD LED Module

Not actually a sensor — it's a full-color (RGB) LED.
You could just buy a plain RGB LED, but this module has the color labels printed on each pin, which is convenient.

Write a PWM analog value of 0–255 to each non-GND pin to light it up in the corresponding color.

Infrared Tracking Sensor

The manufacturer's page describes it as detecting infrared light, but in practice it reacts to the presence or absence of an obstacle in front of it.
The module emits IR light itself and detects the reflection from an obstacle — hence "detects infrared light."

Outputs a digital HIGH/LOW result.
Pins left to right: GND, VCC, Digital PIN.

There's a trimmer pot, so you may be able to adjust the sensitivity threshold.

Infrared Obstacle Detection Sensor Module

Also detects obstacles with infrared. So what's the difference from the tracking sensor above?
My guess is this one is designed to detect objects at a greater distance. Probably.

It has 4 pins but the rightmost one is unused.
Outputs a digital HIGH/LOW result.
Pins left to right: GND, VCC, Digital PIN.

Since it has a standard IR LED and IR receiver on board, using the rightmost pin (EN) might enable sending and receiving remote control signals — but I haven't tested it.
The trimmer pot's function is also unclear.

This is getting long, so the rest will follow in a later post.
15 sensors still to go.