servo malfunctioning

[barney]

We suspect we have one or two servos malfunctioning

I put all the of the legs even with the power off. when I turn the unit on the rear leg immediately goes all the way up.

press 0 does nothing

pressing 8- does make it dance so it is working. But the rear right leg does not move sideways as indicated above.

So we have an up and down issue and a sideways issue.

Can you help?

[spierce]

Hello,

I apologize for your troubles. Would you mind plugging the two faulty servos into a different (known working) servo port on the mePed PCB to verify that you get the same results? I’d like to rule out the possibility of the servo port on the PCB being faulty as opposed to the servos themselves.

Also, please ensure that the Nyloc nut on the bottom of leg that won’t move side to side isn’t too tight. If the nut is too tight, the servo may not be strong enough to move the leg as expected.

Thanks,
Scott Pierce

[barney]

Thanks. for the response.

The front right was giving me trouble so I placed each of the other three legs in the same position. all of them were able to perform the wave function properly. I believe this indicates that the servo in the front right is out.

I do suggest you build in a default program that would test each of the servo functions. This would be really helpful after build to watch the movement of each servo and confirm proper functionality.

[barney]

hey there. I was able to loosen the bolt on the front right foot and now it does perform the wave. JOY.

next problem.

when I turn the unit on two of the legs (front right and rear left) raise the unit up. the other two remain in the same position. I've tried starting with the all legs up and all legs down, but it always ends up in the same leaning position. with two legs up and two legs down.

when performing the wave- all legs go down the front right performs the wave and then the two legs push up to the tetering position again.

for the dance- all legs come down and it does a rocking motion- then the last few moves seem to be off.

pushing 0- has no effect

trying to do any of the walking and turning buttons makes the unit kind of shut down.

your assistance is greatly appreciated.

[spierce]

Hi Barney,

I'm glad you were able to make some progress with your mePed! It sounds like for your first issue of the robot tetering on two legs, you'll need to adjust two of your Leg Servo Arms. Referencing page 4, step 9 of the mePed Assembly Manual and this picture:

mePed Leg Position.jpg (120.97 KiB) Viewed 96607 times

If you look at the legs to the left and right of the picture above, you'll see the position the Leg Lift Servos should be in, pointing slightly downward. All four of the Leg Lift Servos should be in this position. It sounds like two of the Lift Servos are in this position and two of them are slightly off. For the two that don't match the above picture, remove the screw referenced on page 4, step 9 of the assembly manual, gently slide the Leg Servo Arm off the servo spline, and then rotate the leg until it matches the other servos. After you have the correct rotation, push the Leg Servo Arm back onto the servo spline and replace the servo screw. This should fix your walking and dancing issue.

Pressing the 0 button on the remote will make the mePed move all the servos to their centered position. This is the same position that the mePed starts at when powering up the robot or after various movements such as dancing, waving, and bowing. The servos were probably already centered when you pressed the 0 button, which is why there wasn't any noticeable change.

As for the mePed shutting down, please see this thread: viewtopic.php?f=8&t=4. Your PCB will already have one of the diodes removed so there is nothing to do on that front but you will most likely need to use a set of fresh, good quality batteries or NiMH rechargeable batteries with at least 2,500 mAh of capacity.

I hope this helps!

Thanks,
Scott Pierce

[barney]

This explanation was very helpful and my robot now is working well. Thank.

Next step learn some ardrino coding tricks to make it do some fun stuff.

[spierce]

Hi Barney,

I'm glad you were able to get your mePed up and running! Please let me know if there's anything else I can do to help.

Thanks,
Scott Pierce