mePed Forum

After carefully assembling my new mePed, I was disappointed when I first turned it on. Two of the legs moved to between 5 and 10 degrees away from the 45-degree "centered" servo position, and attempts to use the remote did not cause the robot to move correctly (a few movements, then it stopped). It seemed horribly broken!

However, after trying several of the suggested fixes on several of the posts here, I now have the mePed WORKING FINE! Since I had to weed through several of the posts to find the right clues, I thought I'd summarize what seemed to be the major basic troubleshooting checks, in case it helps someone else. Here's what worked for me:

• USE RECHARGEABLE BATTERIES: Even fresh alkaline batteries are not likely to provide the necessary current. Try using NiMH rechargeable batteries with a full charge - 1900 mAh worked for me, but spierce recommends at least 2500 mAh.
• LOOSEN ALL LEG HINGES: I was very careful to make sure each joint was easy to move, but tight enough to remove any "play" between leg pieces. Apparently, this was still too tight - as spierce suggests, start out with all nyloc nuts just a little loose, allowing slight play between pieces. This helped one of my problems.
• RE-ADJUST SERVO ARM CENTERING IF NECESSARY: Even though I was careful to set the servo center position per the instructions, the arms moving off-center after turning on the mePed could be caused by inadvertent servo positioning during assembly, or inexact matching between mechanical centering and electrical centering done by the program. I loosened/removed the servo arms where they were off-center after power-on, and re-positioned them on the server splines where needed to get better centering. Re-test by powering on the mePed, and wait for the center command to re-position all servos. All the joints can be adjusted enough after assembly, if care is taken.
• CHECK REMOTE OPERATION WITH IR SENSOR LED: Verify the plastic tab has been removed from the remote's battery compartment, then check that the red LED on the mePed's IR Sensor board (part 28) lights up or blinks while a button on the remote is pressed. This worked fine on mine, but others have had issues here.
• INTERFERENCE CAUSES DUPLICATE COMMANDS, NOT NEW COMMANDS: Sometimes, using a new command on the remote (like turn, after going forward) seems to just duplicate the last command instead of performing the new command. The MePed is programmed to perform the last good command, if a new command from the remote is not understood. Commands from the remote can be interfered with by fluorescent lights and other IR interference. Try pointing the remote directly at the IR sensor, or removing possible sources of interference. Check the remote's battery.
• HUM COMING FROM SERVOS: Some hum may be heard from the leg servos even when standing still - usually most of this hum is normal. The servos may be trying to center themselves or retain their current programmed position, especially the vertical leg servos as they attempt to hold the weight of the mePed. To check this, lift the body of the mePed off the table/ground, and tap on the top of each leg to relieve any pressure on the servos. The humming will normally stop or at least reduce in volume, indicating the servos have positioned themselves fully. But remember that some humming is normal during operation.

Hopefully this summary may help someone find a quick solution to a common issue. Please feel free to add a post to this topic if I missed any basics, or if you have a correction to the above. Details for most of the above items can be found in other topics and posts.

For some diagnostic software, see my post titled "Diagnostic Functions and Program" in the mePed Software forum. Documentation and links to the code attachments are there.

Hi RockyMtnMark,

Thank you for the great recap of common issues, and your additional insight, that people face when getting their mePed working for the first time. I couldn't have said it better myself!

I should update the user manual to instruct users to plug in all the servos into the mePed PCB and power it up to center all the servos before beginning the assembly instead of manually rotating each servo by hand to find center. This would probably eliminate most, if not all, the calibration issues people have.

Thanks again,
Scott Pierce

Thanks, Scott.

To further assist people in troubleshooting some types of issues, I've written some diagnostic routines for the mePed. See my post in the mePed Software forum, titled "Diagnostic Functions and Program" - documentation and links to the code attachments are there.

Mark