Fan module, L9110
A small DC motor with a soft propeller on an L9110S driver board, run straight off two board pins. Aliases: L9110 fan module, mini fan module.
The chip on the board is a whole H bridge, run from the module's own VCC, so the two
inputs are logic pins and there is no transistor to add.
Pins
| Pin | What it does |
|---|---|
INA |
High (with INB low) spins the fan one way. |
INB |
High (with INA low) spins it the other way. |
VCC |
Supply for the chip and the motor, 2.2 V to 6.5 V. |
GND |
Ground. |
The inputs
| INA | INB | Fan |
|---|---|---|
| low | low | brake |
| high | low | forward |
| low | high | reverse |
| high | high | brake |
analogWrite() on one input with the other low sets the speed: the motor brakes in
the low part of each period and drives in the high part, and the propeller averages
the two.
Properties
voltage is the supply that gives full speed, 5 V. inertia is how slowly the
propeller follows a change, 250 ms, an assumption for a light propeller.
While it runs
The propeller turns, and the readout shows the speed in percent of full, negative in reverse.
What the model gets right
The truth table. It is the L9110S's, with no coast: equal inputs brake.
The input levels. Low is under a quarter of VCC and high is over 0.7 of it, so a
3.3 V board on a 5 V module is not a high: 3.3 is under 3.5. Run the module from
3.3 V too, or use a 5 V board.
The supply. Under 2.2 V or over 6.5 V the chip does nothing here.
What it does not model
The motor's current and the sag it puts on a weak supply, and the air.
Common mistakes
Driving it from a 3.3 V board with the module on 5 V. See above.
Leaving one input unwired: the chip cannot tell what it is, and the fan stops.
See it in action
Thermostat fan speeds the fan up as a TMP36 warms. Open it at /templates.