Servo

Archiver

Goodevening i am back in town.
Can i modifie a servo that now don't rotate?
it's a servo from Robbe.

kind Regards
Willem

Archiver

How could I wire up a servo to work on a switch with out useing the
BS2

Archiver

I don't think you can.
The Servo wants signal which is normally
at 0 volts. The positioning signal is a
high pulse -- where the pulse width
specifies the position. It wants the pulse
repeated every 20 mSec to 50 mSec.

For example, to center a servo requires a
1.5 mSec pulse. You can easily generate
this with a BS2 with PULSOUT ServoPin, 750
(since the BS2 PULSOUT counts in 2 uSec
intervals).

So:
ServoLoop:
PULSEOUT ServoPin, 750
PAUSE 20
GOTO ServoLoop

The Servo works this way because vendors
have made radio-controlled equipment for
model planes and cars and boats which
generates and uses this kind of signal.

I suppose you could purchase a Futaba
radio control set, and use its equipment
to move the servo.

Otherwise, there is no way in the world
that you can throw a switch on for 1.5 mSec
+- 2 uSec, then turn it off, then wait
20 mSec, then do it again. As a human,
you simply can't cycle that fast.

--- In basicstamps@yahoogroups.com, "uebermenchens"
<uebermenchens@a...> wrote:
> How could I wire up a servo to work on a switch with out useing the
> BS2

Archiver

You could use a 555 timer with an inverted output.

Thad

> --- In basicstamps@yahoogroups.com, "uebermenchens"
> <uebermenchens@a...> wrote:
> > How could I wire up a servo to work on a switch
> with out useing the BS2





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Archiver

If your intention is to make the servo move to two different positions
depending on the position of a switch, you could use a 555 timer
circuit. You could use the switch to select different resistors to
vary the pulse width to the servo. If you just want on and off, you
could also use a 555 timer circuit to move the servo. The difference
is that when the power is shut off the servo will not return to where
it was. Hope this helps.
Lee




--- In basicstamps@yahoogroups.com, "uebermenchens"
<uebermenchens@a...> wrote:
> How could I wire up a servo to work on a switch with out useing the
> BS2

Archiver

How can I wire up an unmodified servo that rotates 180 degrees to
rotate 15 degrees per hour. I tried to modify to pulse count but it
didn't work

Mark

Archiver

> How can I wire up an unmodified servo that rotates 180 degrees to
> rotate 15 degrees per hour. I tried to modify to pulse count but it
> didn't work

You could wire two 555's; The first to sweep a voltage to represent the 15
degrees per hour (or you could just use a cheap R/C timer) and use that
voltage to control the phase of the second 555; this one wired as an
asynchronous PWM generator. (You could also use a dual 555, the 556).

What do you want it to do when it hits the 180 degree limit? Reset to zero?
Sweep back to zero at 15 degrees per hour? Or just stop?
--
Enjoy,
George Warner,
Schizophrenic Optimization Scientists
Apple Developer Technical Support (DTS)

Archiver

When it hits 180 I would like it to stop

mark

Archiver

I truly can't grasp or understand how to get a servo to rotate 15
degrees per hour on a 180 degree motor? How can I do It? Is there
a simpler way?

Mark

Archiver

1. You need to realize that you can't set the
servo to 'degrees', you can only sent it pulses
which move it to certain positions.

2. Having said that, there certainly must be a
mapping between pulse width and degrees. Thus
if a 1 mS pulse is far left, and a 2 mSec pulse
is far right (180 degrees) then 1.5 mSec is 90
degrees, etc. You should be able to draw a
linear graph of pulse width to degrees position.

The equation of a line is: Y = mX + b, where
'b' is an offset (1 mSec) and 'm' is the slope
(in this case, 1 mS/180 degrees is 5.555 uSec
per degree).

So, 15 degrees would be (15 * 5.5555 uSec) +
1 mSec, or 1083 uSec.

3. So, for a 180 degree sweep, 15 degrees per
hour mean you'll do the entire sweep in 12 hours.
You knew this, of course.

4. So, the first hour goes from 0 degrees
(1000uSec) to 15 degrees (1083 uSec). Now you
just have to divide that into 2 uSec 'steps',
use the BS2 to 'PAUSE' that long, and then increment
a 'step' variable by 2 uS and output it to the
servo.

Oh, by the way, the servo wants to be refreshed
every 20 mSec to 50 mSec -- so you may add up
20 mSec 'pause' 'ticks' to get the number of
seconds per 'step'.

--- In basicstamps@yahoogroups.com, "uebermenchens"
<uebermenchens@a...> wrote:
> I truly can't grasp or understand how to get a servo to rotate 15
> degrees per hour on a 180 degree motor? How can I do It? Is there
> a simpler way?
>
> Mark

Archiver

You'll have to figure out what Pulsout value you need for 15,30,45....degrees from one end.
Set servo to one end
Send to 15 degree position
Wait 1 hour
Send to 30 degree position
Wait 1 hour
...and so on

>
> I truly can't grasp or understand how to get a servo to rotate 15
> degrees per hour on a 180 degree motor? How can I do It? Is there a
> simpler way?
>
> Mark

Mike DeMetz N9GEZ
Elkhart, IN
mailto:n9gez@q...
http://www.qsl.net/n9gez