Making Furniture Interactive

October 11, 2007

Muscle Wire

Filed under: Tools — gregsaul @ 1:29 am

Constructing the muscle:
what you need
cut
cut blur

afterCutCrimp

Crimp

measuring wire
wire getting cut

crimps wire

Crimp Open

Crimp Close

final muscle

How to work out what resistor you will need:

If you do not have a resistor in series ( in front of) your muscle it is likely to burn up.

muscle wire circuit diagram

The equation to work out what resistor you will need in series with your wire is :

resistor (Ohms) = (power supply(Volts) /current required to make the muscle move(Amps) ) – total resistance of the muscle (Ohms)

First of all find the diameter of the wire your using:

Measure the length of your muscle wire you will be using in one wire:

Use the datasheet listed above to look up the Resistance (Ohms/Inch) and the Approximate* Current
at Room Temperature (mA) of your muscle wire.

Note down what voltage you will be putting through the muscle wire. (this should be done using a transistor and from a separate power supply NOT from your computer through the arduino )

Now that we know the voltage the length of our muscle wire, how much resistance it has per inch (Resistance (Ohms/Inch)) and how much current it wants (Approximate* Current) . we can use ohms law to calculate what resistor we’ll need.

For example we’re making a muscle out of a piece of 0.008″ Dynalloy Flexinol Wire, our muscle will be made of 2 inches of Flexinol Wire and we are using a 9 volt power supply. Using the dtasheet we find the 0.008″ wire has a resistance of 0.8 Ohms per inch and wants 610 mA of power in order to move.
So we have the following.
Voltage supply (V) = 9v ;
Resistance of our muscle in Ohms = 0.8 * 2 (inches) = 1.6Ohms

note, you should also double check the actual resistance of your muscle by measuring it with a multimeter as there are many factors that can change it’s resistance.

Now using ohms law we find that if we did not use a resistor in series with our muscle the muscle would be getting 9 (volts) / 1.6 (Ohms) giving the muscle 5.625 Amps of current, this is far to much current as the muscle should be getting 610mA or .61 Amps.

To find out what resistor we will need we use the equation 9 (V) / 1.6(Ohms) + x(Ohms) = .61(Amp) where the value of x is our resistor in Ohms, so if we rearrange the equation we find that x = (9 (V) /.61 (A) ) – 1.6 so X = 13.15 so we will need a resistor around 13.15 Ohms.

Because a lot of current will be running through this resistor you should use a high wattage resistor these are usually physically bigger.

Where to buy:

http://www.robotshop.ca/home/products/robot-parts/motors/actuators/flexinol-en/index.html

You can buy muscle wire from many places on the internet, but the cheapest I’ve found it for is here.

Technical info:

http://www.robotshop.ca/PDF/flexinol-technical-data.pdf

You need this to work out what resistor you will need in series with the muscle.

Links:

http://www.mrsec.wisc.edu/Edetc/cineplex/OHP_NiTi/index.html

demo’s of different ways of using muscle wire.

http://en.wikipedia.org/wiki/Muscle_wire

Wikipedia on Shape memory alloy

http://www.benhopson.com/

nothing to do with muscle wire but a must see for kinetic sculpture.

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September 26, 2007

Group jameco order notice

Filed under: Tools — gregsaul @ 5:47 pm

Hey guys,

Tiago and me are making an order from jameco tomorrow after interactive furniture. If anybody would like to order anything as well and maybe share in the shipping let me know either tonight via email gregsaul@gmail.com or in class tomorrow.

Jameco’s good for general components resistors, transistors etc but also has plenty of motors sensors tools etc and can be found at http://www.jameco.com .

September 12, 2007

A useful website for understanding circuits

Filed under: Greg Saul,Sandbox,Tools — gregsaul @ 9:46 pm

This is a simple website that explains how many circuits and components work.

http://www.kpsec.freeuk.com/

Hope it’s useful to somebody.

Portable Arduino!!!

Filed under: Alastair Firth,Examples,Resources,Tools,Uncategorized — afirth @ 1:26 pm

sorry it’s so late, blame Kodak. hit more for the sketch on how to run your arduino off a 9volt

(more…)

August 29, 2007

resistors and LEDs

Filed under: Course Materials,Tools — mdgross @ 8:32 pm

Here is a useful tool for checking the value of a resistor.

Here is a useful tool for figuring out how big a resistor you need for an LED

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