Can I use a 9v DC wall adapter instead of 9v battery to power a motor in a series circuit? ?

Question

Also, the end of the wall adapter ends with a male connection (circular with the center being a small hole [pretty typical]). Is it safe to connect wires directly to that male connection (inside hole and outer metal for positive/negative)?

Lastly, would the addition of a potentiometer serve to control the speed of the motor? If not, what device could I use?

Thank you very much.

Answer 1

Be Careful !!!

Expect a lot of Voltage fluctuations across the other components in series circuit (Load Resistor / Potentiometer)

with change of load on motor (infact Rotation per Minute of motor)

Normally, If motor gets jammed / halted / locked / is showing Zero Rotations Per Minute,

Max Current is drawn

When, it's rotating at top speed, least current is drawn

V=IR

R is constant at constant temperature, so voltage fluctuations across series potentiometer / any other circuit might damage it ...

Also look at the Ampere Hour rating of Adapter

Or you could end up melting the transformer coil inside it.

How abt Best Answer?

Answer 2

Yes you can use an adapter.

A potentiometer is not a good way to control the motor's speed, neither is a series resistor.  Both of them are very lossy.  

A much better way, albeit much more complicated, is a pulse-width modulated supply.  You can Google for a suitable design.

n.b. A wall adapter doesn't have an ampere-hour rating, it has a maximum current rating.  

Answer 3

Yes, the 9V DC adapter will work for the motor, and a potentiometer in series will drop the supplied voltage to the motor and allow you to control its speed.  As for the connection, I'd recommend just cutting the connector off and soldering the wires to the motor, instead of trying to work with the adapter head.  Alternatively, you could find a suitable female connector and solder the motor wires to that.