What resistor for a miniature 3V DC motor

[gl_au88]

Hi there,

I am trying to reduce a miniature DC motor to 1 RPM.

The specs of the motor at Load is:

Load Torque 2.3 RPM
Load Current 0.23A
Supplied by 3V.

Is my calculation below correct?

To reach 1 RPM thus 3/2.3 = 1.304 V = 1 RPM
Take out 1.3V across the Motor, you'll have 1.7V across the resistor.
V=IR
R=V/I
V=1.7, I=0.23
R=1.7/0.23 = 7.39 OHM Resistor

Many thanks,
Garvin

 

[audioguru]

A DC motor needs a high current to start. Your series resistor will prevent it from starting to run.
If you have the correct running voltage for the motor then use gears or pulleys to slow it down.

 

[Mr RB]

If it runs at 2.3 RPM with a 3v supply, you could try a regulated supply of about 1.5v or so.

An LM317 regulator and two resistors can give you a regulated DC supply down to 1.25v. You could google for "LM317 voltage regulator schematic".