The backpack print from Shapeways has arrived!
Overall I am very pleased with the quality of the print. The walls are only 1.22 mm thick which makes the design somewhat delicate with the standard plastic material, so if I had to print it again I would thicken them. The dimensions perfectly match the screws, battery and back of robot chest, so the backpack fits in without any problems. I should have also added a few more holes around the sides, as the wiring is fairly cramped. The battery cabling is fairly awkward, maybe I should have gone with an even smaller one than originally planned!
Along with the battery, the backpack also houses the SMPS2Dynamixel servo power adaptor and a bunch of wiring. The power adaptor has a tricky shape with servo connectors at a right angle to the DC jack, but I was able to use a smaller plug with its plastic casing removed in order to fit it inside the limited space.
Hopefully the battery is close enough to the centre of mass, and not too high, so it remains to be seen if the servos are powerful enough to keep the robot standing and moving upright. Now it is back to software, to get the robot to finally do some interesting moves!
Most of the parts for the Bioloid’s power supply have now arrived. Here are some pictures of the Pi 2 being powered by the 11.1 V, 5500 mAh battery. The battery also powers the SMPS2Dynamixel adaptor for the Dynamixel servos. The step-down to 5 V for the Raspberry Pi is performed by a 3A UBEC (Universal Battery Elimination Circuit), which has a handy MicroUSB output. This seems to be the ideal way of powering the Pi, rather than e.g. via the powered hub or GPIO pins, which bypass the voltage protection, especially when considering that the Pi has to power the peripherals. The USB2AX for the servo control is powered via the Raspberry’s USB port, as will the A-Star MCU.
5500 mAh LiPo battery powering Raspberry Pi 2 and Robotis hardware.
Conky running on Raspbian!
Raspberry Pi 2
The Pi is currently running Raspbian and now also has this great 480×320 touchscreen from Adafruit! I installed ROS Indigo from source using this guide. I have also added Conky on the desktop, a lightweight and fully customisable system monitor, as a way of directly visualising the Pi’s current status. The touchscreen feature of the screen will be of use in the future, if some simple GUI is made for the robot.
The next picture shows the current hardware layout of the whole robot. As there is a lot to power, I went for the beefy 5500 mAh battery, but as it weighs 417 grams, I might have to eventually get something lighter for the robot to be able to carry, at the expense of a shorter run time.