Aerobox - a Soft Robotics Control System

Soft robotics is a new field of robotics that has been really heating up lately. Many soft robots are pneumatically actuated, meaning they move when they are filled with air. To fill these robots with air, many projects use syringes or squeeze bulbs that can be used to manually control the soft robot, such as in this tutorial (https://www.instructables.com/id/Air-Powered-Soft-R... This is great for simple soft robots, but if we want soft robots to function on their own, we will need an electronic pneumatic control system to inflate and deflate them autonomously. There are a few control systems around the Internet already, such as this one from the Soft Robotics Toolkit: http://softroboticstoolkit.com/book/control-board. Many of these are unfortunately very expensive and often overkill for small soft robots. This is where the Aerobox comes in. The Aerobox is a simple, battery powered, single output control system. It's single output is perfect for grippers and single actuators.

Materials:

Tools:

3D Printer
Soldering iron
Hacksaw
Vice for soldering and sawing
Flush snips
Wire strippers
Super glue
Computer with Arduino IDE and Trinket library

Step 1: Solder on Headers

Take the header pins that came with the Trinket and clip them to size. Solder them onto each side of the Trinket.

Step 2: Circuit Diagram

Start by following the circuit diagram/schematic. It is best to start by just making the on-board connections, namely the wires connecting the Trinket and the L293D. It is helpful to color code the the different wires, like VCC - red, GND - black, Signal - Green. For help following schematics, check out this tutorial.

Step 3: Tubing

To build the tubing needed, cut two 1/2 inch long pieces of the 1/8" tubing. Connect one piece to the output of the pump and the other piece to the white end of the valve. Then, connect the two short legs of the Y-connector to the other ends of the short pieces of tubing.

Step 4: Pump and Valve

To connect the pump and solenoid valve, solder wires to the pump and tin the ends of the wires on the valve. Solder them to the motor driver as shown in the diagram. Make sure the pump is connected to pin 1 through the motor driver and the valve is connected to pin 0 through the motor driver.

Step 5: Battery Clip and Switch

To connect the battery clip, start by sniping off the barrel connector. Then peel apart the two wire and strip their ends. Solder the ends to BAT and GND on the Trinket. Then cut the red wire about an inch from the board. Strip the two new ends and solder them to the middle and one of the side pins of the slide switch.

Step 6: UBEC

To connect the UBEC, cut the red and black wires of the battery clip about an inch from the clip itself. Then cut the wires of the UBEC on both sides and strip all ends. Solder the ends of the UBEC to the black and red wires on either end of the circuit. Reference the diagram for this. NOTE: Make sure the UBEC is facing the correct way. The side with the capacitor should be the INPUT. Make doubly sure that this is correct, or else the Trinket could unleash the blue smoke monster.

Step 7: Test

Power on the Trinket by plugging a 9v battery into the battery clip. Flip the slide switch if it is not already on. If all goes well, the pump should activate cyclically (this is because the indicator LED is also connected to pin 1, causing the pump to pulse when the LED does. This will only happen in bootloading mode.).

Step 8: Cut the Board

Measure out a rectangle that is 58mm long and 55mm wide. Draw this rectangle around the electronics on the perfboard as shown in the pictures. Cut along the lines with a hacksaw until you have the cut out board with all the electronics. Depending on how rough your cut was, you may want to sand it down a bit.

Step 9: 3D Print the Case

Print both .stls on standard resolution with 5% infill and 2 shells. Supports are not necessary.

Step 10: Magnets

To attach the magnets to the case, you must make sure they are oriented the correct way. Here is an easy way to do that: get two pairs of the magnets and keep them separated in pairs. Orient the 3D printed parts so the holes for the magnets are facing upwards. Squirt and bit of superglue into each hole. Then, separate the pairs of magnets and press them into the holes. Make sure to reference the pictures for help. Let the glue cure for a few hours.

Step 11: Assembly

Once the glue has cured, you can slide the board into case. Make sure the battery is under the board and the switch is aligned with the notch on the front of the case. Also ensure that the end of the Y-connector sticks out of the hole.

Step 12: Operation

In order to use the Aerobox, you need to have an understanding of how it works. In order to inflate a soft robot the Aerobox must close its valve (by setting pin 0 to HIGH) and turn on the pump (by setting pin 1 to HIGH). To deflate, the Aerobox must open its valve (by setting pin 0 to LOW) and turn off the pump (by setting pin 1 to LOW). I've attached some well-commented Arduino code. To upload it, plug in the Trinket, and while the red LED is still blinking, press upload in the Arduino IDE. For help setting up the Arduino IDE and installing the Trinket hardware folder, look here.

To connect a soft robot, have one end of a piece of 1/8" tubing connected to the robot and have the other end connected to the Aerobox's output.