Dual 6 Servo Question

Question

we have two 6 servo arms connected to the board on ports D0-D13. We programmed all servo to 0 min and 100 max. when i try to center all 12 motors the two arm suddenly begin to move randomly without my input. I was wondering why this happens and what can i do to fix it? confused

Rich · Answer

What servos are you using? And how do you mean moving randomly? It could be due to the servos not having enough torque to move the arms. It could be due to the servos drawing too much current. It may even be the power supply not having enough charge. First check your power supply is OK, fully charged and capable of providing enough current. Next check the servos are not drawing too much current for the EZ-B. The EZ-B is rated at 5A max. If they need more than that you will need to provide external power to the servos. Finally, check the servos are rated with enough torque to lift the arms.

Team 2.5 · Answer

Rich, We are using standard servos with 180 degree rotation capabilities. (This arm was made by Ez-robot. It is the 6 servo arm.) The servos move and operate perfectly fine when each six servo arms are operated independently. The issue is when we start to move both arms. In EZ-B i center all 6 servos on one arm and about 4 servos into centering the other, the two arms begin to move without me inputting any keyboard commands (that what i mean by randomly moving). The power being supplied is enough because we just started using a fresh set of batteries.

Rich · Answer

I'm not sure on the current draw of the standard servos (are they the ones from EZ-Robot too?) but it sounds like they are all drawing a total of more than the 5A that the EZ-B can supply. Does each servo work on it's own without problems? And the problems are only when more than around 4 servos move at one time? If that is the case then I would suggest wiring them up to an external supply rather than to the EZ-B. It's simple to do and there are a few posts lately which describe the method. But basically, you only connect the signal wire to the EZ-B, you connect the VCC and Ground to an external source (it can be the same battery powering the EZ-B). If the source is above 5v you may require the use of voltage regulators, again details have been posted in other topics recently (I'll search in a second and find a link for you). You may need more than 1 regulator too. What power source are you using? The 6xAA battery pack which come with the EZ-B? Or something different?

Rich · Answer

Check Post #2 of this topic for more on an external supply.

Team 2.5 · Answer

Yes. All of my servos are from ez-robot. And i am using the 6xAA that comes with the EZ-B. Each servo does run on its own without problems. The problems does not occur when trying to run 4 at one time. It is when i have initiated all six servos to center on one arm and then try to center the 5th servo on the second arm. I believe that the power supplied to the board keeps the servos locked in position when i center it, so maybe i do not have enough power supply to the robot. So i will try adding an external supply.

Team 2.5 · Answer

ok thanks

Rich · Answer

Bear in mind you may need to upgrade the power supply. The 6 x AA batteries may not be able to provide enough current to move and/or hold all servos.

Team 2.5 · Answer

ok i will keep that in mind. Thanks for all the help and advice!

jstarne1 · Answer

@Team 2.5 - Hello I hope you found the community helpful. Could you mark the thread as answered. Thank you - Josh

Team 2.5

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