Hi Tim,

My electronics skills are fairly good, I have built many projects over the
time.
What I was wanting to do, is have a control box in the shack with a readout
and left/right controls. And have the provision to also be able to have a PC
control it.
I like the Pitch-prop motor, as it is strong, and can be controlled easy.

The way I control it at the moment, is via a 2 voltage system.
The pitch-prop runs at 36volts for full speed, and when I wish to slow it
down for small movements, I use a second set of controls at 15volts. Not the
best way of doing it, but it works.
I then look out the window and see where it is pointing. I know where N, E,
S, W are on my section.

As to price on the parts, I would like to keep it down to around a couple of
hundred dollars.

Regards and thanks for your input.

Kevin, ZL1KFM
www.qsl.net/zl1hk

"Tim Wescott" wrote in message
...


Excepting the readout, this should be a fairly routine motor control
problem. Depending on what you want to do your control box could be as
simple as a current-limited power supply and a couple of switches or as
complex as a fully fed-back motion control system.

How's your electronics skills, and how fancy do you want it to be?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

wrote:

Richard,
Agreed on the suitability of an analog solution... I certainly made
some steps toward critically damped operation. My circuit design was
bad, though.

I didn't have a very analyzable problem; the rotator rotates one of
those fiberglass surplus military masts with respect to another, so I
get a lot of stick-slip, especially if there's a breeze (there are 12
feet of mast above this thing).

This is not to say a suitable set of P, I and D couldn't be found, and
it would have been pretty slick if I'd set up right for empirical loop
tuning, but I hadn't done that. I got pretty close by soldering
components in and out.

I would have had a better time with a real multiple op amp circuit with
a knob for each of P, I and D.

I think you hit the nail on the head regarding too heavily dampened
with too much gain in the antenna rotator case. I just couldn't really
tune the thing.


In my case, I just decided to throw up my hands and go to the simplest
method so I could get on the air with a rotating antenna. I have a
quite successful analog servo going every day with my remote antenna
tuner (www.n3ox.net/projects/servo). That one is ever-so-slightly
underdamped, proportional only, and works nicely. There's a little bit
of hysteresis and it certainly could be improved, but I stopped at the
good-enough-for-daily-operation level.

I guess what I meant by "going digital" was that depending on whether
you're more comfortable with programming than a soldering iron (not
me!) you might think about having a simple motor drive circuit and
implement the admittedly complex PID loop in software/firmware.

You're absolutely right that you can't do this if you don't know how to
do the analog...

73,
Dan
N3OX

Written with the implicit assumption that you'd want to do it in
software, but quite applicable to analog solutions:
http://www.wescottdesign.com/article.../friction.html

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Hey Kevin:

http://www.wescottdesign.com/articles/pidwophd.html
http://www.wescottdesign.com/article.../friction.html

If you want to control it from a PC I'd suggest that you drive an H
bridge from a microprocessor, with a PID controller in there to make it
go. The biggest key to making a PID loop without doing a bunch of math
is to keep your ambition under control -- if you have to go fast, then
you need to delve into theory.

As pointed out, PID control can be tricky -- even though I'm a control
systems professional there's a good chance that if I did it rev 1.0
would just use the micro to implement virtual buttons, with feedback
control for rev 1.1. You definitely want to make sure all the pieces
are working before you close the loop.

Kevin & Natalia wrote:

Hi Tim,

My electronics skills are fairly good, I have built many projects over the
time.
What I was wanting to do, is have a control box in the shack with a readout
and left/right controls. And have the provision to also be able to have a PC
control it.
I like the Pitch-prop motor, as it is strong, and can be controlled easy.

The way I control it at the moment, is via a 2 voltage system.
The pitch-prop runs at 36volts for full speed, and when I wish to slow it
down for small movements, I use a second set of controls at 15volts. Not the
best way of doing it, but it works.
I then look out the window and see where it is pointing. I know where N, E,
S, W are on my section.

As to price on the parts, I would like to keep it down to around a couple of
hundred dollars.

Regards and thanks for your input.

Kevin, ZL1KFM
www.qsl.net/zl1hk

"Tim Wescott" wrote in message
...


Excepting the readout, this should be a fairly routine motor control
problem. Depending on what you want to do your control box could be as
simple as a current-limited power supply and a couple of switches or as
complex as a fully fed-back motion control system.

How's your electronics skills, and how fancy do you want it to be?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html





--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html