The design echos that of the original project, though this version was done from scratch. The bot is roughly twice the size of the original. Each "leg" is completely independent, not joined as in the single motor design. This allows us to use a separate motor for each side. That in turn gives some control over turning.
The mechanical design is fairly clever, moves in a truely bizarre manner, makes a good amount of noise on a hard floor [the author's son's dog is weirded out by bots in general, but is especially bothered by this particular design], and is fairly resilient to tipping over.
Image used under fair use license found here: https://en.wikipedia.org/wiki/File:Ministry_of_Silly_Walks.jpg
This last point isn't as much of an issue with the version we'll be building due to it being wider in proportion to the original: while the height and length has been roughly doubled, the width has been substantially more than doubled to accommodate not only two motors, but also the CRICKIT and a larger battery pack.
Electrically, it is simply two DC motors connected to a CRICKIT. The FeatherWing CRICKIT was used so that we could use the Feather M0 Bluefruit. This lets us easily interact with the robot using the Adafruit Bluefruit app.
If you're not familiar with using DC motors with CRICKIT, see this guide.
You can use a 3xAA battery holder with Alkaline AAs or opt for a large LiPo battery and a boost converter to get the 3.7v to 5v. The former is cheap and easy, but has proven to not always work well with motor based projects due to voltage fluctuations caused by the motors. See the WobblyBot guidefor a discussion of this. This project does use two motors as opposed to the five that the WobblyBot uses, so this isn't as much of a problem.
Maybe a bigger (at least more annoying) problem is that motors can drain Alkaline AAs pretty quickly and they aren't rechargable. An alternative is a 4xAA holder with NiMH AAs. They're rechargable, but do have to be removed for charging. The large LiPo+boost is a far better approach [in the opinion of this maker] as it provides plenty of power and charging is a matter of simply plugging in a USB cable. The boost converter gives you the ability to add a handy power switch as well.
Regardless of how you are powering the CRICKIT, if you are getting weird behavior from the Feather (e.g. crashing/resetting, especially if the bot gets stuck and the motors stall) you can try adding a separate, smaller LiPo (1200mAh is a good choice) directly to the Feather. Recharging this one is simply a matter connecting a USB cable to the Feather.
As always, when you're working on the bot at your bench/desk you can use a wall wart power source to avoid any battery issues.
Operation Tips
The Feather M0 Bluefruit was selected to make remote control of the bot easy. Simply install the Adafruit Bluefuit app and connect to the bot. Select the controller and control pad and use the arrows to drive the bot around. We have a guide on the app that walks through its features and operation.
The bot works best if both legs are in sync. On the original design this was a direct result of using a single motor. In this version the legs are independent, so jostling back and forth a bit to get them aligned before charging forward will result in much better locomotion.
This uses the high torque, all-metal-gear TT motors. Even so, the motors are called on to generate significant leverage. One result is that moving forward works well, but the motors have a harder time with reverse. If it's having trouble getting going in reverse, try swinging the legs to the other extreme before trying to move. This will allow some momentum to be built up before having to lift the body.
Page last edited March 08, 2024
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