Power & brown-outs
- Why does my mePed keep resetting when it tries to move?
A "brown-out": the servos pull the battery voltage below what the Arduino needs. Use fresh, high-capacity (2500 mAh+) NiMH batteries. Boards sold after October 2016 already have the one-diode fix.
- My mePed twitches and resets on walk commands even with good batteries. What else can I check?
Loosen the leg pivot screws, test servos one at a time to find a bad one, and don't use a LiPo pack (it will over-volt the Arduino and servos).
- Is there a hardware fix for brown-outs and noisy IR?
Members report that a 220-330 uF electrolytic capacitor across the 5V rail (e.g. in the Bluetooth header) eliminates the brown-outs.
- Why does my mePed buzz and seem stuck when it stands still?
Some servo hum is normal, since the lift servos hold the robot's weight. Jitter and resets point to a brown-out.
Remote control & IR
- My mePed centers its legs at power-up and then ignores the remote. What's wrong?
Check that the red IR indicator LED blinks when you press a button. Remove the plastic battery tab from the remote and check the battery orientation. A servo that jams or runs hot is probably faulty.
- Why does my mePed repeat the last command instead of the new one?
If it can't decode an IR command, it repeats the last good one. Aim the remote at the sensor, avoid sunlight and fluorescent light, and wait half a second between buttons.
- My mePed walks forward and stops, and sometimes ignores turn commands. Why?
Comment out the ultrasonic distance call (distance = get_distance(INCH);) in the starter sketch. IR interference causes the repeated commands.
- Will the HC-06 work with iOS, and what if the IR receiver almost never works?
An unreliable IR remote is probably faulty and should be replaced. Any Bluetooth module works if its Power, Ground, RX and TX pins are wired to the matching pins on the board.
Servos & calibration
- Is there a summary of the basic troubleshooting steps?
Use rechargeable batteries, loosen the leg hinges, re-center the servo arms, check the IR LED, and keep IR interference down.
- One servo won't rotate when I try to center it. Is it defective?
An unpowered servo should turn by hand without humming. A powered servo locks in the center position. If it still misbehaves, replace it.
- One leg drifts off-center at power-up, and the robot only walks forward. What should I do?
A leg that drifts further every step means a faulty servo. Point the remote at the sensor. The ultrasonic sensor is off by default (call get_distance() yourself). Use an HC-06 for Bluetooth.
- A leg won't move or the robot teeters on two legs. How do I fix it?
Swap ports to tell a bad servo from a bad port, loosen tight Nyloc nuts, and re-seat the Leg Servo Arms so all four lift servos match the reference photo.
- A servo swings all the way to one side at power-up. What does that mean?
If the problem follows the servo when you move it to another port, its potentiometer is faulty and the servo needs replacing.
- One servo rotates fully one way and ignores commands. Any other diagnostics?
If it misbehaves in every port, it's a bad servo and needs replacing.
Hardware, parts & building
- Any tips for fitting the hex nuts in tight spots during assembly?
Hold the nut with needle-nose pliers while you drive the screw from the top of the leg plate.
- Where can I get 1/8" (3 mm) material to cut my own mePed body?
Try MDF from a lumber yard or Inventables.com, 3 mm acrylic, or 3D-printed parts.
- My 3D-printed parts come out tiny in Cura. How do I scale them?
The parts were drawn in inches. Scale them by 2540% (25.4x).
- Which MOSFET does the mePed use?
None. The TO-220 part is a 3.3V regulator, and the servos run directly from the battery pack.
- Are there build photos I can follow?
A member posted a step-by-step build album on imgur.
Programming & software
- The starter sketch fails to compile with an IRremote error. How do I fix it?
A conflicting RobotIRremote library is the cause. Rename its IRremoteTools.cpp (or install the z3t0 Arduino-IRremote library).
- How do I upload sketches from a Mac? The serial port isn't detected.
Install the CH340 USB-serial drivers from the Source Files section of the mePed v2 page, and select Arduino Nano.
- Uploading a sketch fails with avrdude "programmer is not responding". What now?
Use the desktop Arduino IDE, select Arduino Nano and the correct port, and install the CH340 drivers.
- Is there a diagnostic program to test each servo?
Yes. A member wrote lift and pivot tests on IR buttons 7 and 9, plus a stand-alone servo range tester run from the Serial Monitor.
- The servo test program reports "out of memory" in the Arduino IDE. Why?
Select Arduino Nano and the correct port, and try a different IDE version (1.8.5 is known to work).
- Can I use Bluetooth with the mePed v2, and which module works?
Yes. The board's 4-pin header takes an HC-06 (or the middle 4 pins of an HC-05). You can build your own app with MIT App Inventor.
- Has anyone ported the mePed code to a Raspberry Pi or Python?
Not that we know of.