I was wondering if there are any common household devices from which I can get a small DC motor (I have a 9V battery...) to use with a breadboard? It'd take me a long time to buy one so I was hoping to just extract one from somewhere instead...
Sources and types of small DC motors:
- Easy guide: if it has a motor and is solely battery operated it should be useful.
There are two main type of "DC" motors.
"Brush" motors that use a segmented commutator and brush contacts (often actually pieces of carbon) to keep the DC feed to the rotor in proper "alignment" with the magnetic field as the rotor spins. I'll use the term BM or "brush motor" for these.
Look at the small DC motors sold as such at hobby or model or electrical shops. These will almost all be brush motors. Look at one end (usually the end where the wiring is connected, and see the commutator (copper striped cylinder that the brushes bear on and brush holders. In some these will be easy to see, in others almost impossible. You can usually tell these by them having a slightly gritty feel when turned - as the brushes run on the commutator.
A true DC brush motor may have only 2 leads. A BLDCM with an internal controller can also have two leads. Any DC motor with only two leads can generally be operated by applying the correct voltage.
"Brushless DC motors" / BLDCM / BLDC motor. In these, rather than using brushest to switch the DC to the rotor, they (usually) have a permanent magnet rotor and switch DC to the stationary field coils using electronic switches (usually transistors). A BLDCM is like a stepper motor that has position sensing feedback devices that tell the ntroller when to provide the next motor signal. Without this feedback the controller cannot oprated the motor correctly.
- These are close enough to stepper motors that turning one of these by hand will show you the characteristic "lumpiness) (cogging, saliency) that is caused as the rotor moves from magnet pole to magnet pole. Some BLDCMs are "ironless" and will not have cogging.
A "Stepper Motor" can be thought of as a specialist BLDCM where there is no controller per se. WIth a SM the control circuit says 'do one step" and assumes it has happened. They are really a specialist AC motor.
SO both BLDCMs and Brush motors type can be run from a battery but the second type needs to have it's control circuitry included. Some BLDC motors have the control circuitry internal, making them as easy to use as brush type motors. Stepper motors are usually too specialised for easy stand alone use.
Any battery operated motor is almost certainly a DC motor of one sort or the other.
Good & easy: Battery powered toys that operate wheels, elevators etc will almost always contain brush motors. Dismantle and use. Proper voltage can be determined roughly from the voltage originally used. May use low grade open cage gearboxes to reduce rotation rate. Toys and tools are the most likely source.
Good, easy, usually more powerful Small battery powered power tools usually use brush motors. Battery screwdrivers are useful as there are very cheap versions available and they have a gearbox to slow the rotation rate. Useful for eg small robot wheel drives etc. Often use a multistage "planetary gearbox" - useful for high reduction ratios. Google knows.
Good usually Purely battery or battery/mains motorised appliances will usually have DC motors - eg electric toothbrush, razors, battery belnders, ... . Mains powered motorised devices will usually have either unsuitable high voltage brushed universal motors (vaccuum cleaner), mains only shaver, maains only drill ... or unsuitable induction motors or unsuitabloe "shaded pole motors".
Varied Printers usually contain a number of DC motors. These may be BMs, BLDCM's or pure stepper motors. Old printers get throw out in their millions. Finding which motor is of what type in them is part of the learning experience.
Good but mechanical issues Computer type "Muffin fans" that operated on 12V or 5 V almost all contain DC motors. These are almost always BLDCMs but as the controller is inside the fan they can be used in the same way as a BM. The fan blades can be removed and usually the cooling loss would be OK. Hard to mount.
BLDCM or stepper Hard disk, floppy disk, CD/DVD ROM drives. These are usually either stepper or BLDCMs. The controller is usually either on a PCB that the motor is mounted on or cable connected to the motor. By retaining the controller the motor cam be used. 1.44 MB disk motors are BLDCMs - some have very compact controllers on a removable PCB that mounts the motor. Some Samsung 1.44 MB FDDs were superb in this respect. Others are very entwined with the drive PCB. [[Michal notes he found 2 x brush motors in a CD with one moving the head. In floppy drives I've only ever seen stepper motors for head movement - so sounds like a CD could be useful. Platter/disk motir in CD/DVD/Floppy/HDD is liable to be a BLDCM. ]]
Use of 9V battery with fan
A 5V fan will operate "rather fast" from 9V. A 12V fan may operate.
For a 5V fan and new 9 V battery, use a series resistor of
R = 4000/I
where I = fan mA on spec labl.
eg for I=100 mA use 4000/100 = 40 ohm.
Closest = 39 ohms.
As battery runs down a smaller or no resisuor is OK.
Best is to use a 5V regulator and 5V fan. LM7805 or similar.
With a 100 mA fan a 9V "PP3" battery will last about 5 hours.
I've recently got some motors from an old CD-ROM drive.
- 2 brushed motors (one was powering the CD-tray, the other one moved the laser)
- 1 brushless motor (this one spun the CD)
Job-lots and dollar stores often have battery powered 'personal fans' or cheap toys, stuff like that, which are almost always built around low voltage DC brush motors - though 1.5V or 3V will be encountered more often than 9V.
Small hairdryers typically use DC permanent-magnet motors, using part of the heater as a dropper.
-old electric razor, you might be able to find more than one in there
If you have any mechanical things lying around, they are likely to contain DC motors.