Hello guys,
Me and my friends are doing an Arduino project, we ordered all the components, but we missed the resistors, and we realized that some stuff would burn if we don't use them. However we cannot determine which resistors to order, there are many values.
Here are the components we got, that might need resistors:
US1881 hall effect sensor (3.5 - 24 V)
RGB - SMD (WS2812) (5V)
We would really appreciate it if you help us decide which Ohm/Watt resistors should we use for each one of the components above.
Thanks you very much
Hello and welcome.
In order to stand a chance of answering your question please provide a schematic showing how you are proposing to wire up the components you have and where you think the resistors should go. Hand drawn and photographed is fine.
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While you are at it, please also read General guidance and
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You are more likely to get helpful answers if you provide the information requested.
You might also like to read Ohm's Law and Kirchhoff's circuit laws
These laws are fundamental to all electrical circuits and if you learn them a lot of the mysteries of electricity will become clear. In many cases applying both laws to a circuit will provide whatever answer you are looking for.
Thank you.
Pro tip: order a set of something like 20x 30 values. 1/4W is good for almost all applications, especially when working with low voltages the need for higher wattage is extremely rare.
This will often leave you with values you never use, but much better chance to have the value you need (or something close, or can be constructed from 2 or 3 resistors) when building and testing a new circuit. Then you can always order the correct value and add it to your collection.
The Hall effect device is an open collector switch so needs a pull-up resistor to function. That can be the internal pull-up resistor (enabled by pinMode(INPUT_PULLUP)) on each digital pin or a 10K external pull-up.
It is recommended, for WS2812 strips, to have a 470 Ohm resistor between the output pin and the data in of the strip.
I agree with wvmarle that buying a cheap assortment would be a good investment.
groundFungus:
I agree with wvmarle that buying a cheap assortment would be a good investment.
Preferably one that comes with a compartment box. At the very least, one compartment per decade, preferably two. 
270 LED current limit
330, 470, WS2812B data line series resistor if 1st LED is far from the Arduino. I have not used for distances of 3-4 feet and not had issues.
1K LED current limit
2.2K I2C pullup or LED current limit
3.3K I2C pullup
4.7K I2C pullup
10K button/switch pullup
I find that is all I have been using the last 9-10 years across almost all Arduino projects.