noob project, cool idea, need help...

[regaljohnston]

hi,

i bought a lens thinking it would be compatible with the zoom button on my camcorder, unfortunately it isn't ...

i've been looking at building an servo motor to control the zoom function, this will be better for me because i'll be able to place the control stick/trigger exactly where i need it on my camera rig.

i have a few of specifications however...

-it will need to be as quiet as possible (for obvious recording reasons).
-it needs to be variable speeds.
-able to ease in and out of zoom smoothly/seamlessly.
-the control needs to be operatable by my thumb alone, a left/right thumb-stick or seasaw peddle would be ideal.

i've drawn up a very basic schematic of my idea-

(the control stick will go on the handle of the poleroid chest stabilizer, shown below)

a servo tester was suggested for the controller. it needs to be a thumbstick/sea-saw peddle which will allow me to operate with smoothness and precision. like the libec controller shown above.

not sure, but perhaps something like this?-
http://www.555-timer-circuits.com/servo-tester.html

as for the motor, somebody said i would need a continuous rotation servo... suggestions? must be quiet and able to ease in and out smoothly. i don't know where to begin choosing continuous rotation motors so a few suggestions would be greatly appreciated... please provide links also.

please help me, let me know what your approach would be.

thanks!

regal johnston...

 

[George]

Looks interesting, I have one suggestion. Get rid of the belt drive in favor of a simple wheel drive. Use a rubber wheel where the pressure of the wheel against the focus part of the lens. A drive belt would be hard to keep in place as it might walk itself off the area it needs to be on. You would not have that problem with a rubber wheel that just presses up against the focus on the lens.

If you are still working on this let me know and I will gladly help the best I can.

George

 

[xptical]

Take a regular servo and remove the bottom plate. De-solder the circuit board from the motor. Now you have a DC motor running through step-down gearing to the output shaft. Extend those wires outside the case. Replace the bottom cover and remove the top cover. Find the gear with the travel-limiting pin. Usually the biggest gear in the stack. Use a small saw to remove that pin. Put it all back together.

Servos take 4~6 volts. Running any more through the motor might cause damage.

Anyway, at that point, you'd have a fine-control, gear-reduced motor.

Use a 555 PWM controller to drive the whole thing. Maybe get creative and use a POT to control the speed of rotation.


Is there an easy way to reverse the PWM signal though? Maybe connecting dual timers with one reversed and diodes to stop feedback?