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Author Topic: Pen plotter, rc servo up and down?  (Read 2579 times)

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Pen plotter, rc servo up and down?
« on: May 11, 2015, 10:54:57 PM »
Hi all,
        Got an new project coming, building a pen plotter.
 I want to use a RC servo (RC servo used in radio control planes) for Zaxis up and down, how do I connect the RC servo to the breakout board (c10)?
Breakout board Z axis output:  Pulse, DIR, Common
RC servo                             : PWM, +3.3, GND
Do I need a interface between the BOB and the RCservo?

thanks,



Offline BR549

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Re: Pen plotter, rc servo up and down?
« Reply #1 on: May 12, 2015, 10:27:23 AM »
Mach3 only does Step/Direction for axis outputs. You would need to convert the Step/Dir to PWM to drive the servo.

(;-) TP
Re: Pen plotter, rc servo up and down?
« Reply #2 on: May 12, 2015, 09:04:51 PM »
Thanks BR549.
Before I ask where I can get this "step/dir to pwm" board?, couldn't I use spindle output and pwm control in spindle setup?

Offline BR549

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Re: Pen plotter, rc servo up and down?
« Reply #3 on: May 12, 2015, 09:50:20 PM »
You probably could make the servo MOVE but you will have ZERO control over it as the spindle output is constant  . It would be far easier to just use a simple solenoid to raise/lower the Pen into position.

(;-) TP
Re: Pen plotter, rc servo up and down?
« Reply #4 on: May 13, 2015, 08:14:10 AM »
Hi,
I used to fly RC quite a bit years ago. From memory the Futaba servos I used required (I think!!) 0.5ms pulse to
drive to full extent one way and 2.5ms pulse to drive full extent the other way and the refresh rate was about
20ms. That would require a base PWM frequency of only 50Hz. Not sure that spindle control PWM as enacted
by Mach would do that.

Craig
My wife left with my best friend...
     and I miss him!
Re: Pen plotter, rc servo up and down?
« Reply #5 on: May 13, 2015, 09:32:50 PM »
Thanks to both BR459 and Joeaverage.
Looks like there are more info. on Solenoid than RC servo. Will go for Solenoid 1st then RC servo.
Did a search on solenoid for Mach3, for z axis up and down some people use M code (coolant or mist), I think I will use DIR to switch up and down via a relay, so when relay is on the pen goes down and off the pen goes up, so when Z= -1 then pen goes down and Z=6 pen goes up.
Below is an gcode example for engraving:
G00 G49 G40.1 G17 G80 G50 G90
G21
(Engraving)
M6 T3
M03 S2000
G00 Z6.0000
X75.0000 Y0.0000
G01 Z-1.0000  F300.0
G17
G03X-75.0000I-75.0000J0.0000 F400.0
X75.0000I75.0000J0.0000
G00 Z6.0000
M5 M9
M30
 please let me know what you think.

thanks,