I ended up finding one that works very well. But I'd love to
understand why. It is marked as Rf-330tk-07800
Those markings match the Mabuchi Motor designation scheme:-
So in RF-330TK-07800 the R means round, F is precious metal brushes, 33 is the armature diameter and case length (corresponding to ~24 mm case diameter by 21 mm long), 07 is the wire diameter and (most importantly) 800 is the number of turns per armature slot.
Here's an example which includes the 'design voltage' (D/V) of 3.5 V, which is the typical operating voltage in the design application:-
Does anyone know how this differs from a simple 1.5-3V DC motor?
In comparison to a 'simple' 1.5-3 V DC motor, the main difference is that this one is designed to run at lower speed, which is achieved having many more turns of fine wire on the armature.
When power is applied to a DC motor it initially draws a high current limited only by the winding resistance. This current creates torque which makes the motor speed up. As the armature turns it generates a voltage proportional to rpm, reducing the voltage across the winding resistance which reduces current and torque until it balances the internal torque load (bearing friction, magnetic drag, air resistance etc.) and any external load. With no external load it will continue increasing speed until the generated voltage almost reaches the supply voltage.
When the motor is driven mechanically it generates the same voltage (proportional to rpm), so if it runs at eg. 1000 rpm when powered by 3 V it should also generate 3 V when spun mechanically at 1000 rpm. Having more turns reduces motor speed and increases generated voltage because the current passes through a greater length of wire and so generates more voltage as it crosses the stationary magnetic field.
A standard LED can light up on very low current, but needs between 1.7 V to 3.2 V (depending on color) to do it. To generate this voltage from a small airflow you want a motor that has low friction, low magnetic drag, and low cogging, as well as low operating rpm. This could be either a motor designed to run on a voltage close to what you need, or designed for a higher rpm at a proportionally higher voltage.
Your motor is designed for efficient operation in low rpm, low current, low cogging applications such as CD players and air fresheners. This makes it a good choice for your project. Other motors that might be suitable include small higher voltage motors (eg. 24 V) designed for low power applications. For example this motor only does 1700 rpm at 24 V, so it should generate 3 V at only 200 rpm!
