Braided Model

Today is a very exciting day for our group!  We successfully built a single-row prototype of our design!  This prototype contains 6 LEDs and two lengths of thread.  Figure 3.3 below shows the test strip lit up.

 

 Figure 3.3 - Test strip lit up

We started assembling the model last night.  The procedure gave us good practice for the final design.  Figure 3.4 below shows our solution for drying the glue.  We did not want to use a blow dryer for fear of blowing the LEDs off the string, so we used a curling iron!

 

 Figure 3.4 - Creative glue drying solution

We're making final preparations for our full model, so sit tight and we'll report back ASAP!

-The team

Week 3

This was a very productive week!  To start, we conquered the thread resistance problem.  We measured the resistance between three distances of thread in three different configurations: a single strand, a twisted pair and a braided triplet.  The results are shown in table 3.1 below.

Table 3.1 - resistance of thread by number of strands

It is apparent that the more strands braided together, the less resistance there is in a given length of thread.

The second breakthrough we made was lighting up an led using the thread as wire as shown in figure 3.2 below.

Figure 3.2 - led illuminated using conductive thread as wire

Prior to this lab session, we were successful in making the led function as part of a circuit.  We discovered that the issue was the assembly mechanism we are using to build the led matrix.  This mechanism is a metal, therefore conductive, loom.  As the loom is conductive, it was shorting the circuit.  

These advancements should allow us to sting the loom over the course of the week, possibly gluing the LEDs to the matrix before next lab.  

-Brandon

ps. Here is a video of the led turning on and off:

Conductive Thread Woes

     I was testing out the conductive thread we have available to use and I found what may be a problem: the resistance per length of thread is so high that when a power source is connected a small distance away from the LED, it does not light up!  Upon further investigation, I found that when the probes of an ohmmeter are placed approximately one cm apart, the resistance is between .5 and 1 ohm - an acceptable amount.  However, when the probes are placed approximately 10 cm apart, the resistance jumps to between 5 and 10 ohms - too high for reliable usage. 
     One solution to consider is braiding multiple strands of wire together in an attempt to lower the resistance per length of thread.  Another possible solution is switching to another material - maybe even metal wire - to build the prototype.  This solution would allow light measurements to take take place in order to see if the project is worth pursuing in the future. 

-Brandon

Week 2

Last week in class we met our advisers and were able to choose our groups and projects. We created our blog and our bios page.  The project we chose was the Wearable LED for Photodynamic Therapy.  
Our challenge is to create a wearable LED device that can be used with pc4 to treat psoriasis.  By using 100 LEDs, a lilly pad, conductive epoxy, and conductive thread, a prototype can be built.  
During week 2, we met with our instructor and discussed ideas to build the LED strip.  We discovered many potential problems while brainstorming.  Some tools we still need to properly build the device include a multimeter, and model tweezers.  The LEDs are very small which makes it incredibly hard to glue them to the string by hand.  The use of tweezers will decrease the difficulty of this task.  Also, we do not know which end of the LEDs is positive, and which end is negative.  Before we can proceed, our group would like to be certain which end is which.  We also needed a ruler to measure the distance apart the LEDs needed to be mounted. Another problem is that the loom on which we were to build the device is needed for other groups.  Since the glue takes four hours to properly adhere, a new mount needs to be devised.  The mount should be non-conductive and portable.  Some ideas that were suggested include cork board and blocks of wood. 
We will obtain the needed devices, and bring them to lab next week.  This way we will be able to begin building the device immediately.

 First attempt at stringing LEDs on a Nativie American loom