Responsive Fabric
These days, more and more new smart materials expanding the versatility of fiber and at the same time redefine what we can do with textile. Before exploring other design possibilities with this material, I need to ask myself: how can I connect and control these materials so that they can speak to each other and I can speak to them?
So, my goal in this final project is to understand how to connect the smart material (Nitinol) with the conductive fabric as the medium, the arduino as the microcontroller, and the processing as the user interface in order to perform a kinetic behavior to the fabrics. (Nitinol is perfectly fit with the textiles in terms of its size and dimension, instead of using a motor.) As a beginner in this field, I learn by following one great example, in this case Marcelo Coelho’s Shutter Project , and try to create the similar procedure and function.
Component
I use Lilypad Arduino 328 as the main board to read the program, and attached the nitinol connection to its 6 pins. The Nitinol Biometal Helix (BMX15020, dia: 150 uM) originally contracted as a coil at 20 mm length and can be elongated until as twice as much of its original size (40-50mm) by attaching a 30 gram force. To pull the wire to move back to its contracted length, its need to be activated by heating it with 70 C temperature or with a voltage of 3 Volt battery. I use 100 Ohms resistor to reduce the current from transistor to lilypad and 4.7 ohms resistor to reduce the current for the nitinol. Apparently, I don’t need the second one since the current that fed the wire got too many resistances while it goes along the zelt. (In other words, if I can calculate the required length to reach a certain resistant, then I might not need a resistor at all, and that would make a seamless connection on the fabrics). As for the switch, I use Transistor TIP122 PNP to read the arduino program of which flap should be activated. (Base goes to the Lilypad, Emitter goes to the negative, and Collector attached to the nitinol).
Scheme
In terms of design, I see circuit board analogous to the space programming process in architectural design. Accordingly, I created a blueprint of my circuit design using a simple SketchUp program for the following reasons:
- To anticipate the dimension of the component, such as the transistor or resistor size whether they are colliding or not, and the lilypad mainboard orientation so each pin would have enough space to be connected with.
- To trace the positive and negative connection whether they are overlapping or not.
- To use the vector graphic image for further fabrication process, for instance, cutting the shape on the rapid prototyping machine or stitching pattern on the embroidery machine.
- To design and simulate the physical appearance of the project as a whole by rendering the material.
With this technique, we can get a sense of the scale of how the final product will look like just by printing the scheme on the paper. However, it is still not able to predict the performance of the design as a circuit board. Since all the connection nee ds to be perfectly connected by whichever joint that we use.
Connection
As the most used technique in this scheme, ironing the zelt is very easy to do, however, I have to make sure that every joint is perfectly blend to each other. To attach the wire with the zelt, I use a metal bead and crimped the bead while the zelt and the wire were in its hole. Any other component with the pin, transistor and resistor, are solder to the zelt. The only way to test whether they are perfectly assembled is to make sure that they are beeping continuously in the multimeter.
Procedure
The goal of the procedure is to have the flaps move as the mouse position is over the dot on the shutter controller (see the screen). The procedure are the following: on the Shutter Controller, IF the mouse position is over the dot THEN the processing will send information (i) to the arduino. In the arduino, IF it’s receiving the information (i), THEN the arduino told the mainboard to turn on the PIN (HIGH). In the circuit, IF that PIN on the mainboard turn on, THEN the transistor will let the current feds the nitinol connected to that PIN so it will contract and pull the flap up.
Lessons learned:
- Dealing with the resistance and nitinol behavior: To move the nitinol properly, I need a specific value to let the current goes through the wire. If there is too much resistant, it will move very slowly, or doesn’t move at all. If there is no resistant, it will burn the wire. So, I guess it would be nice to spend a good deal of time to get the best value to heat the wire.
- Dealing with the nitinol cost: Due to the scheduling problem, I skipped the part where I should have been shaped the nitinol myself (using a furnace with 500 C), and bought an expensive pre-shaped nitinol coil instead. Because of that, I can't do much with this two 2 cm wire.
- Dealing with the connections: Most of my problems with the connection caused by the lack of rigidity on the part where the component's joint together. So, I need to make sure every joint is connected perfectly at each step, instead of complete connecting the whole circuit at the beginning and then test it afterward.
- Finally, it is highly recommended to test the connection with a simple structure at each level: from arduino to the circuit and look at the connection by using multimeter (LED can tell us that there is a current goes by but doesn’t guarantee that there is enough power to move the nitinol); and from processing to arduino by checking that each the variable is send as it should.
Many thanks to Leah for the guidance and troubleshooting the code and the circuit; and also to Marcelo for the idea of this project. This is certainly one of the best class I ever took