LoCoRo Electronics
The core of the LoCoRo electronics is a Raspberry Pi 3 and a PWM control board (aka RC servo controller). Options other than the Raspberry Pi 3 will work. - examples include a Raspberry Pi 2 + Wi-Fi adapter or an Orange Pi Lite. These alternatives are not directly covered by this documentation but most of the material applies to these variants.
There are a number of options possible for the basic electronics of the LoCoRo. Here are just two of the possible lists. The links which are provided for reference.
Plug-n-play list:
Flexible-builder list:
  1. Raspberry Pi 3
  2. Class 10 Micro SD card (8GB minimum, consider getting 2)
  3. 5v USB power supply
  4. Micro USB cable
  5. I2C PWM Control board
  6. Jumper wires (varies)
  7. Continuous rotation (aka 360) servos, another example, and a package, and micro servos may also be used (2 minimum, 4 optional)
  8. DC DC Converter
  9. 18650 batteries (2 minimum)
  10. Battery charger (often bundled with batteries)
  11. Battery holder
  12. SPST switch, push-button or toggle
LoCoRo electronics picture of list 1
Considerations:
  • There are lots of options for the electronics. These lists are examples and do not imply a preference for products or sources. The lists may be used in their entirety, mixed and matched, or act only as a reference. When possible, use what you already have, patronize your preferred sources, do the necessary research, and shop around.
  • Power is a notable difference between the two example configurations:
    • The plug-n-play configuration uses a two-port battery with one port connected to the Raspberry Pi and the other port powering the servos via the I2C PWM board. In this configuration, the servos are running at 5 volts and will not be quite as fast as with the flexible-builder configuration where the servos are running at 7.4 volts.
    • With the plug-n-play configuration, there is no need for a power button. Power is controlled by plugging (or unplugging) the USB cable. With the flexible-builder configuration, the batteries must be connected to a DC DC converter and the converter must output between 4.8v and 5.2v. The converter output is connected to the Raspberry Pi directly to the GPIO pins. This bypasses any polarity or voltage protection. Care must be taken with assembling and configuring the flexible-builder option.
    • DC converters are available in several configurations. Variations include the input voltage range, variable vs. fixed output voltage range, and optional LED displays. The LED option is handy to know when to recharge batteries. A converter with a preset 5v output eliminates much of the risk with damaging the Raspberry Pi.
    • The flexible-builder option may be upgraded to 12 volts and use 12v DC motors along with electronic speed controls.  The DC DC converter is capable of handing7.4V or 12V input is adjusted to convert to 5V output for the Raspberry Pi. This makes this configuration more suitable if the plan is to build a bigger, more powerful robot.
    DC-DC step down converters
  • If you need to purchase the first four items, consider one of the starter kits as it may cost less than the total of the individual parts.
  • You can convert standard 180 degree RC servos to continuous rotation. Instructions for the conversion are detailed in the second on the robot chassis. This may be a preferable option is you have existing RC servos.
  • Be cautious of budget servos. Some may work. Many of the cheap servos suffer from poor performance and a large dead-zone - the point where the servo is neither rotating forward or reverse.
  • A 5v power supply with micro USB connector may be substituted for the USB power supply and USB cable. The standalone USB cable is still needed in the plug-n-play version to connect to the battery.
  • If you plan to tinker or you will add sensors to the robot, consider a jumper wire kit with breadboard. There are kits with extras such as LEDs, power converter, and switches.
  • If a small amount of wire cutting and solder is an option, then the USB bare wire cable is an easily DIY task.

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