Are "3V6" and specific resistors required?

[AdamRaichu]

(I know this isn't strictly an issue, but I couldn't figure out a better way to ask.)

Your example circuit has a part I don't recognize (labeled 3V6) and resistors with specific ohm values. Are these specific parts/resistors required, or is there a circuit that works with only wires and 10kilohm resistors?

[todd-herbert]

Your example circuit has a part I don't recognize (labeled 3V6)

That part is a 3.6V "Zener diode", something like a 1N4729. Its job here is to lower the 5V output from the Arduino to near the 3.3V level required by the USB data lines.

Wired like this, it acts a bit like a "spillway" in a pond or dam.

Any extra voltage above 3.6V will be "spilled away" to ground by the Zener diode. The 68Ω resistors are there to limit the current; to make sure we don't overwhelm it. (Imagine: heavy rain filling the pond faster than the spillway can handle)

Are these specific parts/resistors required

As for the resistors: the precise values aren't super important. 100Ω would probably work in place of 68Ω, for example.

or is there a circuit that works with only wires and 10kilohm resistors?

This Zener diode circuit is the most commonly used, however it is theoretically possible to use a different circuit, made only from resistors. This isn't really practical using only 10kΩ though. Do you have any other resistor values available?

[AdamRaichu]

First, thank you for taking the time to give such a detailed response!

Its job here is to lower the 5V output from the Arduino to near the 3.3V level required by the USB data lines.

Does it matter that I'm using the the power from the usb port on the motherboard to power the arduino (through a motor shield)?

Do you have any other resistor values available?

I don't think so. 😬 Would it be practical to use the PWM pins instead (to output a weaker signal)? (Or to try to simulate resistance by using a bunch of extra cables or something?) I fully accept that these options may not work.

Forgive me for my lack of knowledge in circuitry.