Control RC Servo with a joystick, hard wired?

[Barkster]

I'm looking to make a camera control for a camera using some type of
joystick. I've seen a few projects to make a servo driver but anyone
have any ideas on how to make something with a joystick, just need two
axis like a joystick. Anyone know how to tie a joystick into one of
those drivers. I'd really like to have two joysticks controlling 4
servos. Thanks

 

[BobG]

Sure. The servos need a nominal 1.5ms pulse that varies 1ms to 2ms over
the lock to lock range of the servo. Couple of 555s should work, with a
3rd one triggering the variable pulse at a 50Hz rep rate.

 

[David Harmon]

On 28 Mar 2006 14:15:08 -0800 in sci.electronics.design, "Barkster"

I'm looking to make a camera control for a camera using some type of
joystick. I've seen a few projects to make a servo driver but anyone
have any ideas on how to make something with a joystick, just need two
axis like a joystick. Anyone know how to tie a joystick into one of
those drivers.

No. You have to use two of those drivers.

 

[Si Ballenger]

I'm looking to make a camera control for a camera using some type of
joystick. I've seen a few projects to make a servo driver but anyone
have any ideas on how to make something with a joystick, just need two
axis like a joystick. Anyone know how to tie a joystick into one of
those drivers. I'd really like to have two joysticks controlling 4
servos. Thanks

A google search for "555 servo" will produce circuits like below
that might can use the pots in the joystick. Might be easier to
hack an RC unit like the bottom link to control the servos.

http://wolfstone.halloweenhost.com/TechBase/svoint_RCServos.html#Testing
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXAAD7**&P=0

 

[Ian Stirling]

I'm looking to make a camera control for a camera using some type of
joystick. I've seen a few projects to make a servo driver but anyone
have any ideas on how to make something with a joystick, just need two
axis like a joystick. Anyone know how to tie a joystick into one of
those drivers. I'd really like to have two joysticks controlling 4
servos. Thanks

It's maybe not quite as simple as the other posters have suggested.
Hooking the sticks directly to devices to generate a pulse train to move
the servos will result in something that works, but the sticks will
control position not velocity.
Sticks central is point straight ahead, if you want it to point to a
specific spot, you've got to hold the joysticks on that spot. (assuming
a central return stick)

 

[Rich Grise]

It's maybe not quite as simple as the other posters have suggested.
Hooking the sticks directly to devices to generate a pulse train to move
the servos will result in something that works, but the sticks will
control position not velocity.
Sticks central is point straight ahead, if you want it to point to a
specific spot, you've got to hold the joysticks on that spot. (assuming a
central return stick)

I worked with some RC servos once, and at the time, there was a motor
controller available, where the stick actually controlled the speed of
the motor, and could reverse it. You would need some kind of end stops -
those RC servos are designed to hold position if they lose the signal;
with a motor controller, if you lose the signal, the motor keeps turning
at the most recently commanded speed and can break stuff if you don't
have some kind of limit switches.

Good Luck!
Rich

 

[Luhan]

I'm looking to make a camera control for a camera using some type of
joystick.

Real easy if you are into microcontrollers. Read the sticks with A/D,
do what you want with the data, then create your pulses in software.

Luhan Monat
"Without Microcontrollers, we're pretty much screwed"

 

[Si Ballenger]

It's maybe not quite as simple as the other posters have suggested.
Hooking the sticks directly to devices to generate a pulse train to move
the servos will result in something that works, but the sticks will
control position not velocity.

The servo will position itself at the speed the joystick is
positioned, fast stick movement for fast servo movement, slow
stick movement for slow stick movement.

Sticks central is point straight ahead, if you want it to point to a
specific spot, you've got to hold the joysticks on that spot. (assuming
a central return stick)

You probably can use the buttons on the stick to switch the
pulsed output on and off using something like a small double
throw double pole relay. A setup could be two 555 chips, one for
up/down, and one for left/right control. The pulsed outputs from
these two chips go through the relay that is closed contacts when
the stick button is pressed. Press the button and move the stick
to position the two servos as desired, then release the button
and the servos stay where they are and the stick can return to
the neutral position. Send the relay outputs to a 6 position dual
contact rotary switch so that up to 6 pan/tilt cams can be
individually selected. I haven't used the 555 chips, but I've
done much the same thing with a joystick connected to a computer
to control my DIY servo pan/tilt cam (below).

http://www.geocities.com/zoomkat/ezservo.htm

 

[Heinz Liebhart]

Real easy if you are into microcontrollers. Read the sticks with A/D,
do what you want with the data, then create your pulses in software.

Why use a uC where a simple NE556 will do? IMO they are still using
some sort of pos or neg puls width modulation.
ok, ok, size is almost the same, u can add ramp behavior, ...

Heinz

 

[René]

Real easy if you are into microcontrollers. Read the sticks with A/D,
do what you want with the data, then create your pulses in software.

Luhan Monat
"Without Microcontrollers, we're pretty much screwed"

Did this with an AVRTiny. Actually the only way to do this
conveniently.

You do *not* want to change the pulses according to the joystick
position (like RC stuff does), you want to increase / decrease pulse
lengths when the joystick is moved, and *leave it there* when the
joystick is centered.
The dreaded 555 will not do that! (unless you add a lot of extra
hardware)
(Any of the 6 ports of a garden variety HEF40106 will make a better
pulse generator if you want to go that way

If no pulse is offered to a servo (make sure it's a low impedance "0")
- the servo will remain at last position.

 

[Barkster]

Sweet camera control, guess it isn't as easy as I thought. I'm not
looking for precision and this is how I stoped my servos from returning
to center. I cut off the prong that moves the pot along with the
control arm gear, thus giving me 360 degrees and stops where I quit
sending pulses. Now if I can only hardwire it, even if I could
hardwire a old controller straght to the servos, eliminating the
reciever.

 

[Matthias Melcher]

Sweet camera control, guess it isn't as easy as I thought. I'm not
looking for precision and this is how I stoped my servos from returning
to center. I cut off the prong that moves the pot along with the
control arm gear, thus giving me 360 degrees and stops where I quit
sending pulses. Now if I can only hardwire it, even if I could
hardwire a old controller straght to the servos, eliminating the
reciever.

How about simply connecting a toggle switch directly to the motor in the
servo? Or directly to the potentiometer (not using any electronics in
the servo)? If your servo needs only very little power (and to move a
camera, it probaly will), just try this. It may burn out the pot in your
joystick, but it may be worth a try because it is probably the simpelest
thing by far:


5V o---------------o----------------------
| |
+-+ |
| | R/2 |
+-+ |
| ,-. +-+
o-----[( M )]-------->| | R pot
| `-´ +-+
+-+ |
| | R/2 |
+-+ |
| <
GNDo---------------o----------------------