Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG

Hi Jason,
a modeller's servo seems to be fine: it has a high torque and while
powered, it keeps its position actively. Disadvantages are their price
and the fact they are controlled by AF PWM / PPM (unless one modifies
them, of course).
A cheap source are scrap FDDs and CD-ROMs: there are 2 - 3 classic and
stepper motors in each of these animals. They are used for positioning
the head, rotating the media, ejecting the CD etc. It needs a bit of
skill and effort to put them into new life, though.

BR from Ivan

(Jason Hsu) wrote in message . com...
Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG

Hi Jason,
a modeller's servo seems to be fine: it has a high torque and while
powered, it keeps its position actively. Disadvantages are their price
and the fact they are controlled by AF PWM / PPM (unless one modifies
them, of course).
A cheap source are scrap FDDs and CD-ROMs: there are 2 - 3 classic and
stepper motors in each of these animals. They are used for positioning
the head, rotating the media, ejecting the CD etc. It needs a bit of
skill and effort to put them into new life, though.

BR from Ivan

(Jason Hsu) wrote in message . com...
Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG

On 14 Sep 2003 21:51:38 -0700, (Jason Hsu)
wrote:

Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG


The military has historically used small DC gear motors, Pittman,
Globe, etc. Fair Radio has these at reasonable prices. The control
mechanism is all analog, classical servomechanism and error detector
and amplifier approach.

Alpha uses stepper motors to turn the tuning and loading caps in the
auto tune amplifier. These are fair size steppers with gearing.

If your control mechanism is analog, look at DC motors. If you are
going to use digital control, think steppers.

Jack K8ZOA

On 14 Sep 2003 21:51:38 -0700, (Jason Hsu)
wrote:

Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG


The military has historically used small DC gear motors, Pittman,
Globe, etc. Fair Radio has these at reasonable prices. The control
mechanism is all analog, classical servomechanism and error detector
and amplifier approach.

Alpha uses stepper motors to turn the tuning and loading caps in the
auto tune amplifier. These are fair size steppers with gearing.

If your control mechanism is analog, look at DC motors. If you are
going to use digital control, think steppers.

Jack K8ZOA

Jason Hsu wrote:

Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG


DUAL 10K LINEAR TAPER MOTORIZED POT CAT# MPOT-10K
http://www.allelectronics.com/cgi-bin/category.cgi

4 dollars.

Also, I've used surplus 1 rpm motors to drive capacitors.
You want DC, small and slow.

Jason Hsu wrote:

Has anyone here used a motor to control a potentiometer or variable
capacitor? (An automatic tuner would be such an application.)

What type of motor do you use? Servo? Stepper? Something else?
What do I need to look for in a motor?

Jason Hsu, AG4DG


DUAL 10K LINEAR TAPER MOTORIZED POT CAT# MPOT-10K
http://www.allelectronics.com/cgi-bin/category.cgi

4 dollars.

Also, I've used surplus 1 rpm motors to drive capacitors.
You want DC, small and slow.