dc motoreaglefanschematics
I have been designing a circuit that involves a 5V DC Fan. When I was creating the schematic on EagleCAD, I couldn't find something that resembles a Fan other than a Motor. Should I stick with using a motor, or should I opt to find a library that contains a much more intended symbol for a fan elsewhere?
TIA
There is a set standard package libraries called ref-packages-* look into ref-packages-smd-ipc.lbr. I usually try to search for a part by using package name: in schematics editor press "add" and enter *msop* (with "*" at begining and at the end) into search field.
I can recommend SparkFun and Adafruit libraries - these can be trusted and usually contain most common packages. This page has a set of decent libraries.
As regarding to devices it's usually faster to make your own than to look for them over the internet. If you download something you never know if you can trust them.
If this is the type of fan you are using: http://www.formfactors.org/developer/specs/REV1_2_Public.pdf
-then the output sensor claims it is an open collector or open drain. (Meaning it only pulls down.) It also says "Motherboard will have a pull up to 12V, maximum 13.2V". Written this way I would take this as a recommendation. If the output is truly just an open collector/drain then you should be able to add your own pull-up resistor as needed. For the Arduino input you would have the resistor pulled up to +5 only. (You could add the 5k resistor as shown, or if you know how to enable the internal pull-up on the Arduino port pin use that, in which case you would not need the 5k resistor shown.) With a resistor in place the fan sensor pulls down (to 0v) then releases the pin, so it then climbs back up to what ever voltage the pull-up is connected too.
The hook up should look like this:
simulate this circuit – Schematic created using CircuitLab
But just as a precaution, before connecting the Arduino Speed input pin to Sense, you should measure the voltage on the Sense fan pin while the fan is slowly rotating (with 12v on the fan power input).
The spec lists the Fan's Control input to be a 5v PWM signal. So coming from the Arduino no extra driver circuit is needed.
Also the spec says the pulses from the Sense pin is 2 per revolution, so measure the pulses per second then divide by 2.
Best Answer
You forgetting the third and simplest option - just create your own symbol. You can also add connector footprint for it to be ready for PCB design.
Seriously, I don't recall any more or less complex projects where I did not need at least one custom element.