Introduction: Reconfigurable Tap Dancing Robots

About: Lining Yao works at the intersection of interaction design, material science, digital fabrication and biological engineering. Her goal is to combine natural and engineering approaches to develop physical mater…

It's a dance dance robot. Tap dance performence involves lots of people dancing on stage. ]

Step 1: Concept

There are several aspects of the concept.

1. Reconfigurable: each module includes one leg, and the legs can be arranged freely to form different geometries.

2. Adjustable/Composable: The tempo of each leg can be adjusted via a rotational button. Six together can form a harmony rhythm.

3. Pre-designed mode: through an on-screen interface, player can select different tap dance mode, and compose movements in real time.

Step 2: Mechanical Design

1)assembling the boards

holes on the boards are cut on Modela small milling machine while milling out the circuit board. Some careful measurement and designed is needed in order to get the position of holes right. As laser cutting is fast anyway, try to adjust the file based on the circuit board if it didn't work.

Step 3: Case Design

press fit laser cut pieces

I used 1/8'' marine plywood for the case. One consideration of selecting wood rather than acrylic is that in case of slight mistakes in cutting, I could easily glue some parts, or sand some edges when I try to press fit different pieces. Holes are designed to firstly, assemble boards; secondly, leave space for flexible cable connections;

Step 4: Making Solenoids

The parts I used include:1/4'' acrylic tube to hole the wires; magnets wires;metal stick as legs;magnets as feet;rubber caps;

A great tutorial on making and controlling solenoid: Some tips: - To wind hundreds of magnet wires around the acrylic tube, you could either use your hand, or use a hand drill/lathe;- Loops are friends; more loops, larger electrical magnet force;- To enhance the magnet force, I attached a small magnet at the bottom of the metal stick which is driven up when the electricity is on. Luckily, the cylinder magnet looks like foot, which is aligned with the project topic of tap dancing;-The solenoid I made can be powered by 8 ~ 12v. If I keep the voltage at 8v, and each high signal sent out through microcontroller lasts for 40milisecond, the solenoid barely became hot, which is good.-The magnet wire is covered with insulation; For connection on both ends, you have to get the insulation layer off with a knife.

Step 5: Magnets Pair for Re-configuring the Arrangement

As each unit has two sides, and I wanted to make sure each side can be connected with any side of the other unit, so I designed a box on each side that can just allow the small magnet to flip and rotate. So when sides from different units are approaching, the magnet from each box with flip automatically to attract each other.

Step 6: Cables for Inter-connections

Three kinds of cables are used in the project. And holes were left there for flexible connections: positive and GND high voltage power connection with the bridge; FTDI cable with the bridge; 6 lines rainbow cable to connect two unit (if the two units are connected clockwise, rainbow cables are aligned the same direction; otherwise, flip the cable for connections)

Step 7: Electronic Design - Logic Structure

The system includes one bridge and five nodes boards. All six boards have similar basic components, which include analog input from potentiometer, digital output to a solenoid, serial communication and power supply. The only difference is, the bridge unit is connected with computer through an FTDI cable, and in charge of communicating the serial information from the computer to himself and the other five nodes.

Step 8: Schematic

As we can see from the schematic, the microcontroller I chose is Attiny 45. Potentiometer is connected with 5V power and a 200ohm resistor, while the analog output is connected with ADC1 pin of Attiny 45; The version I posted here has a voltage regulator, to make sure Attiny 45 get 5v power while solenoid can get more power (FTDI cable can give 5V for microcontroller as well, in that case we could get rid of voltage regulator); From Schematic Part 2, the way to control solenoid is shown. MOSFET is connected with a digital output pin of Attiny45, in order to control the high voltage(8~12v) to go through the solenoid; two parts are critical, the first is: we need a diode (in my case a LED to utilize the wasted power to blink) in parallel with the solenoid; the second is: when MOSFET is connected to ground, we need another diode in parallel. As I printed out one layer board, I threw some 0ohn resistor to jump over some lines.

Step 9:

Components and Boards

I used Eagle to design the board, and export the black and white png image under 1000dpi. I connected some pins from below the board, hhenceI drew holes in photoshop; I've modified the shape of the board as well, to fit the mechanical design for the convenience of assembling; Finally the boards are milled out in Ronald Modela with 1/64''for the traces and 1/32'' bit for the hole and cutout. :eagle file for bridge with voltage regulator eagle file for nodes milling files for original eagle file milling files modified for being longer.

Design files are attached.

Step 10: Control Interface

An interface was built in Processing with some pre-built patterns of tap dances. It talks with the hardware through serial communication. Players can select one pattern and repeat the action, or they can put different patterns in a line and compose their own tap dancing movements.

Step 11: Conclusion


Special thanks to: Neil's enormous courage, passion to work on this project;David Millis and Brian's help on Serial communication/checking, making fuse, etc.Adam's help on Eagle design and Terminals;Moriz and Shahar's help on baud rate, serial communication;Skylar's support on Modela tutorial and logistics;David Constanza's tutorials on laser cut machine, shopbot machine;Daneil's suggestion and inspiration on Solenoid.