Vorpal Combat Hexapod Troubleshooting Guide
Vorpal Combat Hexapod Quick Links:
Servos Can't Lift Hexapod or are Sluggish
- Vorpal can't stand up, servos seem to struggle.
- Vorpal can stand up but during walking it successively loses height, getting lower and lower over time.
Possible causes include:
- Batteries are low or dead. Recharge the batteries. It is also possible that you have batteries that are just no good. Cheap no-name brand batteries often vastly overstate their capabilities.
- Improper surface: Vorpal is designed to work on reasonably smooth surfaces such as tile floor, wood floor, smooth table top, desk top, etc. It will not work on most carpets. There are "carpet feet" being developed by some Makers which may solve this in the future.
- Too much friction on servo bearing. Make sure your 3D printed models are cleaned up, especially the little hemisphere on each servo mount on the chassis, and also the little hemispherical hole in the leg hinges. This hemisphere is the bearing opposite the servo shaft, and if it has drips or other defects there may be too much friction for the servos to move smoothly. Sandpaper any areas that look misshapen or rough, or put a drop of silicone grease on the hemisphere. (Other types of oil will also work, or even petroleum jelly, but be careful and apply with a Q-tip or paper towel very carefully, because some kinds of oil may eat through electronics).
- Legs out of adjustment. If the legs are adjusted such that Vorpal "rides too low" then the amount of torque required to walk increases and the legs may not be able to keep up with the requirements of the walking gait selected. Put the robot in ADJ mode (turn the dial fully counterclockwise to STOP, then slightly clockwise until the knees go out straight). Now, it's not always possible to make the servo horns come out totally straight from the body due to the way servo horns are manufactured. But, if you can't make it come out 90 degrees straight, it's better for the horn to be a little too clockwise than to be a little too counterclockwise. Too clockwise will make the leg lift the robot body a tiny bit higher, which is fine, but too much counterclockwise will make the robot ride "low" and stress the servos more.
- Bad servo. If one or more servos are bad, the other servos may struggle to lift the robot's weight fast enough to keep up while walking. If a servo is obviously bad (chattering excessively, twitching, not moving at all, or clearly not pulling its fair share of the load) then that's the probable culprit.
- Bad BEC. It is possible for the BEC (which is on the battery/switch assembly and provides 5V regulated power to the robot) to go bad if it gets overheated too many times, and in this case it may not be able to output enough amps to keep the legs moving properly. This is the least likely cause, please eliminate other causes before requesting new hardware.
One Servo Doesn't Work
Most likely causes include:
- The servo has gotten unplugged from the servo controller. Open up the hexapod by removing the screws holding down the electronics caddy and check the wiring.
- The servo has a frozen gear. Occasionally when a servo goes to its maximum position it may get stuck there. You will know this is true if the servo won't move easily even with power off. You can usually fix this by turning power OFF, then gently applying pressure to the servo in the direction you would expect it to move until it "unsticks". If the same servo keeps getting stuck, you should replace it.
- The servo has gone bad (either gears are broken or wiring is damaged). There are several possible causes for this, but in any case the only fix is to replace the servo.
- For more information on care of servos to prevent them from being damaged, see the user guide section on care of servos.
One Servo Jitters Constantly
It is normal for there to be some humming sounds while the robot stands as the servos activate and deactivate to maintain the standing posture. But very loud chattering or large twitching motions are not normal.
- This typically means the servo has gone bad and its electronics are not responding properly. First check to make sure the servo's wire is completely inserted in the servo controller, but if that looks ok the only fix is to swap the servo.
Gamepad Won't Control Hexapod
- Make sure the battery is charged in the gamepad and in the robot.
- Make sure the hexapod dial has been turned to RC (remote control mode).
- Make sure the gamepad is turned on and you see lights through the cover.
If you see lights through the holes in the center of the cover, observe the blinking pattern. Here's what the blinks mean:
- NOT CONNECTED: When the Bluetooth modules are not connected, there will be a fast, steady blink.
- IN THE PROCESS OF CONNECTING: When they first start to connect, they will blink slowly at first, then will go dark for a couple of seconds. This process will only take about 5 seconds.
- CONNECTED: When they are properly connected, then there will be a 2 second pause followed by two quick blinks, and this will repeat over and over as long as there is a connection.
The next few sections explain what to do in each of these situations.
Lights indicate connection is good, but robot not responding
This could be because you've not hooked up the wires properly on the Bluetooth module, either the one on the robot or the one on the gamepad. Carefully check connections.
There could be a general issue with the robot. See if it works in DEMO mode. If DEMO mode doesn't work, you probably have an electrical issue and need to check all connections. It is possible you have a bad component (Arduino or Servo controller) and need to contact firstname.lastname@example.org.
Lights never show a connection
If the Bluetooth modules are not paired after about 10 seconds (two quick blinks followed by 2 seconds dark means they're connected properly), then the possible issues are:
- Make sure both the robot and the gamepad bluetooth modules have lights.
- Make sure the GND wire on the nano in the gamepad is properly connected. For example, if you accidentally connected it to something like RST then the nano will have lights and appear to be working, and the Bluetooth modules can even connect to each other, but in reality the Nano is constantly resetting itself and never running the program.
- If you have several hexapods, make sure you're using the correct gamepad that's matched with your hexapod. If need be, open up the gamepad and the hexapod and check the labels on the Bluetooth modules, make sure the labels match. If the labels are different, the two modules won't auto-pair and connect. You may have mixed up modules when building several robots.
- To get further information, flash the gamepad with the DEBUG version of the gamepad firmware and see if the messages are correct. See the article Debugging Gamepad Issues for more information.
No lights at all
If you do not see any lights at all in the center of the gamepad, then:
- The gamepad battery may be low or dead.
- Your Bluetooth module may not be getting power, check wiring, especially the VCC and GND connections. Make sure jumper wires do not fall loosely off the pins, if they do you should swap to a new jumper wire or press on the little plastic tab on the connector with the hex key to tighten up the wire.