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Resolved Resolved by jstarne1!

Doubling Up 2 Servos For More Power

Hi all,

I want to tie and Double up 2 servos for more power. I'd like have the shafts will be tied together and facing each other. This means they would be turning at the same time but in different directions. Also they would be controlled through scripts. Is this the best way to configure them? I can see this may cause challenges in scripting and wiring. Any suggestions on how to set this up in EZ Builder or have a better and different way?

#27  
Yep, those mechanical sounds cover up a lot of annoying sounds.

Your avatar is a little freighting and disturbing. *sick*;)
#28  
Why, thank you! Just call me B(acon)9:D
#29  
Josh or anyone on the know,

As I stated above I want to tie two servos to each other and have them move exactly at the same time and speed (Tandem). Josh Suggested removing the control board in each and replace them with ultrasonsic PWM motor control boards. I found the below board that looks like a good choice.

Motor channels: 1
Operating voltage: 6 16 V
Continuous output current: 12 A
Peak output current: 30 A
Auto-detect baud rate range: 300 115,200 bps
Available fixed baud rates: 300 115,200 bps
Available PWM frequencies: 20 kHz, 5 kHz
Reverse voltage protection?: Yes
USB connector style: USB Mini-B

Pololu Jrk 12v12 USB Motor Controller with Feedback

Now, these little wonders are expencive at $100 each. I'd have to pop anouther $200 to control the two servos I want to run in tandem. Any reasion I cant run two servos from just one controller if the max current draw of each combined is below the 12A Continuous output current of the JRK 12v12 controller?

Here's how I see it working:
Remove the driver boards from each servo
Solder wire directly from the servo motor lugs and ground of each servo
Connect the new servo wires in parallel to the JRK's single motor output (A B).
Only attach one pot from the two tamdem servo's to the JRK's Feedback input.

My thinking is that with both servos being controlled by the same control driver board and only one pot that they should move exactly the same. Only variable would be the gearing in each servo. Hopefully being the same make high quality servo this should not be an issue. Here's the servo from servo City and the Robotzone gearbox I'm useing:

Gearbox


User-inserted image


HS-7950TH Servo


User-inserted image
#30  
Very impressive Anthony! Thanks for the imput. However sadly I have tried the invert method as I mentioned in your Lexi thread. My servos move at slightly different speeds and one travels farther than the other useing the same values. Oddly they are identical brand of high quality servos. *tired*
#31  
Dave, I think I figured out why your dual servos don't work. Take a look at the specs on the servo page
www.servocity.com/html/spg7950a-cm-360_servo_gearbox.html

Specifically, the diagram that defines the movement. Neutral is at 12:00. Time to rotate 180 degrees clockwise is 1900 microseconds, 180 counterclockwise is 1100 microseconds. Evidently it travels slower in one half of a 360 degree rotation, so by reversing one they are going out of synch.

Weird? yes - but that's how I'm interpreting that diagram. Experts: am I correct?
#32  
Humm, It takes longer for the servo to go one way then the other. That would explain it. Wonder why that happens. Thanks, Nice catch. i dont like the answer but it makes sense. Well, back to the drawing board. *sick*