UV Cleaner

Last week I faced a question whether to purchase an expensive piece of equipment for my research work at the graduate school or use something else. I desperately needed an Ultra-Violet cleaner - an oven that cleans surfaces off any organic contaminants.

First of all, for those who does not know ultra-violet light is a quite dangerous thing and definitely should not be played with without the appropriate protection gear. The ultra-violet that everyone (most people) are happily enjoying during sun bathing times is the most harmless (actually, not really, but not as dangerous as other types of UVs) - called UV-A range (around 400nm wave-lenght). Not that many people realize that there are other UV wavelengths that are way more dangerous than UV-A. Those are UV-B and UV-C ranges (other classifications exist). Luckily the ozone layer that surrounds the earth mostly protects us from those and, understandably, that is the reason why there is a fuss around this topic. If not for the ozone layer - we would be exposed to other UV ranges and they are deadly.

For example, 254nm wavelength excites chemical bonds in organic compounds and dissociates them, while 185nm emission creates ozone out of oxygen. The first wavelength is typically used in the germicidal lamps that are used to kill bacteria. Both of them will damage eyes and skin!!! ( eyes, unfortunately, permenantly!!!! so be very careful if you have to deal with it).

When both of 254nm and 185 nm are present an excellent cleaning effect of inorganic surfaces can be achieved. First decomposes organics while second creates ozone that reacts with decomposed molecules and forms volatile species. This cleaning method is well known in semiconductor industry.

Anyway, back to my problem …. several thousand dollars seemed like a big investment for me, therefore, I had decided to build a UV cleaner myself. Moreover, I did some research and found that some of the germicidal lamps (i think they are usually used for water cleaning and duct cleaning but not sure) are actually dual band (produce both wavelengths). Some are available in a small form factor.

I called the company that manufactures the lamp and asked to ship a balance and a lamp-holder in the package. Luckily that had those as well. Total cost was about 200$.

When the lamp arrived I had to find an enclosure for the UV cleaner.

UV Germicidal Lamp

The former router/hub housing was found in the junk in the lab and seemed like a great fit for the purpose.

Former Router/ Now UV cleaner housing

Several drilled and routed holes for the power line connector and a power switch, a couple of holes for the lamp holder, a couple of holes for the lamp balance were made first. Next the electrical connections were done in accordance with the lamp and balance manuals.

Electrical Connections

Unfortunately, I did not make a picture of the bare lamp mounted in the enclosure and thus I am skipping that step. Next, I built a light reflector using bare PCBs: cut the appropriate sizes and soldered together to have a box-shaped frame. Then, I taped that frame to the housing using an aluminum tape.

Light Reflector

Additionally, I have made a lamp fixator - something to hold the free end of the lamp in place. I used a battery holder I suppose (not sure) - part that fit :). The purpose of the 4 bolts with standoffs will be clear later - they are for making a sample drawer slide in/out horizontally and not tilt.

The UV Lamp in Place

The front of the enclosure, thanks to its previous application, already had an opening:

Enclosure Opening

This opening I decided to use as a slot in which a drawer with a sample will be sliding in/out. So the next step was to build that drawer. I used the same approach as for the reflector and used PCB material to build it. Finally, added a handle to it to be usable.

Sample Drawer

Added a PTFE sheet to protect the metal from the UV rays and the drawer was complete. Ah… forgot, I also put a note on the drawer to remind everyone to be careful.

Finished Drawer

At this point I tried everything ON and that is how it looked.

Assembled UV Cleaner

After I ran the system overnight I noticed a pretty bad smell inside the system (besides the ozone smell) and I realized that whatever decomposes in the system stayed inside the enclosure as there were no escape paths - so, I decided to build a ventilation into the system.

I used a computer fan - one of our old computers came with it and we never mounted it so it was laying around for ages. It was time to serve it’s purpose.

A Computer Fan

Drilling holes behind the lamp would serve a purpose of venting the whole enclosure (electronics etc.).

Ventilation Holes

and the mounting holes for the reused part of the fan:

Mounted Fan

Now, I addressed the UV chamber itself. I drilled holes along the sides of the UV chamber:

UV Chamber Vents

Using the rectangular tubing I manufactured the exhaust channels:

UV Chamber Exhaust

Finally, making holes in the plastic fan enclosure and drilling mounting holes for the exhaust pipes completed the exhaust system of the UV cleaner.

Almost done, UV Cleaner

The last part was the fan’s power supply - the easiest option for me was to reuse one of the 12V power supplies found in a junk pile in our lab. A “surgery” brought out a transformer with a rectifier and a capacitor - all that was needed.

12V Transformer

The problem was that it was a bare transformer with no means of fixating it on/to anything. Brass sheets, a bender, and metal cutters came to help followed by drilling, hammering, and jamming.

Transformer Holder

Finally, mounting it inside and making the necessary electrical connections:

The 12V DC supply, Mounted

And that was a final step. Here is the final product

UV Cleaner, Completed

Additionally, for those who interested, here is the effect of the UV on gold:

In normal conditions gold is hydrophobic, in other words, does not wet and a water droplet on the golden surface looks similar to this:

Water on Gold

This hydrophobic behavior is explained by organic contamination that present on the surface exposed to usual ambient conditions. However, after 10 minutes exposure to UV, same droplet looks like this:

Water on Gold Oxide

This indicates that the organic layer has been removed and the surface is covered with a layer of gold oxide that changes the hydrophobic surface into hydrophilic.

Isn’t that fun!!

To describe the underlying phenomenon in simple words: Metals contain a cloud of free electrons inside them that posses particular energies. The energies of a number of electrons in vicinity of the surface could be affected locally by a,  let’s say, some molecule adsorbed on the surface. The effect within the metal depends on the electronic characteristics (i.e. dipole moment) of the molecule. Therefore, if there was a way to detect this change in energy one could say something about the adsorbed molecule.

Contact Potential Difference (CPD) phenomenon

Every metal contains free electrons that are in constant random motion throughout the metal. The potential energies of these electrons are dictated by the atomic structure and could be described by the Fermi level/energy on the energy diagram. Fermi energy may be seen as the maximum energy level that electrons could posses in a metal at the absolute zero temperature. In other words, because of different atomic structures different metals have electrons with different potential energies.

When two dissimilar metals are brought close to each other the electrons in one of the metals will essentially be described by higher energy states in comparison with the other metal. If the metals are not electrically connected, or there is no mean for the electron exchange, the metal’s surface potentials will see no changes. However, once such mean appears a portion of electrons from a metal with higher electronic states will move to the second metal thus creating a transient current. The driving force for this migration is described by the metal electronic cloud cross-talking. The electrons with higher potential energies would gladly migrate to the states with lower energies. Once electrons started moving to another metal it charges negatively whereas the donor metal charges positively. The developed field in the gap between metals characterized by a potential difference is called the Contact Potential Difference. Once again this process has a transient nature - once the electrons re-distribute between the metals there is no net current flowing from one metal to another.

Measurement Technique

The transient nature of the CPD current makes the potential measurement troublesome at the first glance. The charge is trapped in the gap between two metals and the rest of the metal’s potential is unaffected. A simple voltmeter measurement will bring no result as the charges are concentrated in the gap and have absolutely no incentive to come out of there and, therefore, voltmeter will give exactly 0V measurement. However, let’s look at the following equation of electrostatics: Q=CU. It shows that the amount of charge is proportional to the capacitance between the metals. Thus, if we can change the capacitance of the system we can alter the equilibrium in it causing the charge to change. Moreover, if we introduce a periodic change in the capacitance of the system we will start generating an alternating current flowing back and forth between the metals. This current, in turn, is detectable.

So now, when we have understood what we needed to do to make the current flow through the external circuitry, let’s see how we can measure the contact potential difference between the metals.

Lets assume we have two dissimilar metallic plates that form a parallel plate capacitor. Let’s fix in space one plate and vibrate the second one while both plates are connected through a current detector. Of course the shape of the current depends on the type of oscillation - for instance, sinusoidal vibration will cause sinusoidal current.  Now, let’s connect a battery to the static plate and start applying the external potential to it. If we apply different voltages in a several volt range we can notice that at some value the current that was previously flowing through the external circuit disappears. What happened?! The externally applied potential compensated the CPD between the metals and now both of the surfaces are at the same potential. In other words, the applied potential in absolute value equal to the contact potential difference between the metals. This method of the CPD detection is known as Kelvin-Zisman method.

Lock-in Amplifier Basic Theory

Lock-in amplifiers are generally used to extract useful signals from the inputs that are subjects to big noise values or measurements with very small signal to noise ratios.

The idea behind this technique is in the fact that the useful signal is characterized not only by amplitude but as well by the phase. It is hard to encounter a situation when the noise in the system has the same phase and frequency as the signal of interest, unless the system is poorly designed.

One of the necessary conditions that determines if this technique might be used or not in an experiment is the presence of a reference signal. If it is available the measurement can be performed as follows:

A signal acquired from the output of a device can be multiplied by a reference signal that is characterized by exactly same frequency but might have a different phase. The multiplication of two signals represented by a cos() function leads to a difference of the cos() functions - first with phases subtracted and the second with the phases summed. In other words, one of the cos() functions become a constant due to subtraction of equal frequencies, while the second cos() function will have a double frequency argument. The latter can be simply filtered out by a low pass filter. The DC voltage result after the filtration will be proportional to the amplitude of the harmonic of interest - the useful signal.

Other variations of the lock-in amplifiers exist.

Design of the setup

- Vibrating Plate Driver

One of the instability problems can arise when an unstable signal generator is used to drive the vibration of one of the plates: frequency instabilities can detune the lock-in amplifier causing incorrect measurement. The closer to ideal behavior show digital generators. Plus, a stable phase adjustment can be easily achieved using digital circuits.

All the described above, made me choose a mixed design to purely analog. I used a Atmega8 micro-controller from Atmel to generate a sine wave and a reference signal. I am aware of three different ways to generate a sine wave using micro-controllers:

1. using a DAC and a simple filter
2. using PWM (pulse width modulated signal) and a filter
3. using delta-sigma approach with filter

As I the resources of my micro-controller were limited and the budget was not, I decided to go with the simple first option. A DAC with a SPI interface was chosen. A table with 512 points per period was created and fed into the DAC. During the operation of the generator, the phase reference signal is generated in parallel by triggering to two of the points within the 512 given points separated by half period. In other words, the phase of the reference signal can be adjusted within 360 degrees with a 360/512 degree resolution.

- Preamplifier

The signal in the CPD setup is the transient current flowing from one conductor to another. That suggests that a current-to-voltage converter (or a trans-impedance amplifier) to be used in this measurement. There are several advantages of that: 1) high input impedance of the amplifiers along with a high value resistor in the feedback allow for high impedance of the measurement input. 2) convenience of the bias application to one of the electrodes.

The bias can be applied in different ways:

1. through a positive input of the operational amplifier only
2. through a “phantom ground” - shifting the ground along with shifting the power supply potentials

The second approach gives better results as it allows for wider range bias adjustments. Plus, I have experienced strange amplifier behavior with approach 1 with high biases.

- Lock-in Amplifier

The idea behind the control circuit in this particular apparatus is to apply a bias to the measuring input (connected to the vibrating electrode) to make the CPD voltage zero and therefore reduce the current flowing between conductors to zero. Once this condition achieved the voltage applied to the electrode will be equal to the actual CPD developed between two metals.

The control circuit first amplifies the voltage put out by the current-to-voltage converter and then multiplies it by a reference signal that in this case is a square wave of same frequency. An analog switch is used for this purpose. The switch outputs two signals each of which are rectified cos() function one positive and second negative. In other words, it slices the signal along the time axis. Next, the signals are fed into a differential integrator that computes the difference of these two signals and integrates it. The result is further used as a bias voltage for the input electrode.

Let’s say the CPD developed between the electrodes is 0.5V. After the current-to-voltage conversion and amplification we get a cos() signal with amplitude let’s say 0.1V. Next this signal is integrated and let’s say the result is 0.2V. Now this voltage is being fed as a bias to the input causing the voltage difference between the metals to be (CPD-0.2V). Sequentially, the signal after the amplification is reduced due to this reduction. The integrated signal will be 0.2V+v. This process continues until the (CPD-V) voltage will be close to zero and will not cause the integrator to change its value. Finally, the integrator will hold the voltage equal to the Contact Potential Difference between the metals.

- Experimental Setup

The setup consists of a voice coil on a one-axis positioning stage and a sample table made out of aluminum. The vibrating electrode is made of gold. The voice coil is mounted upside down with the electrode on the top. The sample table hovers over the vibrating electrode and has a cut out window for the vibrating electrode to pass through. The sample metal and an optional dielectric are placed on the top of the sample table.

- Selected Results

Here are some stability test results in the laboratory environment over several days.

TBContinued …. Pictures and Figures to come

I have used Bezier curves along with the Tween Effect to accomplish the non-linear motion of an object. Please read here about the tween effect here. Some theory on Bezier Curves is described here.

The idea behind the Bezier curves is very simple - for a given set of point in space a simple parametric equation is created. The equation consists of a all given vectors weighted by a parametric functions.

For instance, for a cubic curve (4 given points) the equation will be:

As you can see when t=0 B(t)=P_0 ; when t=1 B(1)=P_3. When t is in between 0 and 1 the output of B is either approaching P_1 or P_2.

Now, when the underlying curve theory is somewhat covered let’s talk about the tween effect.

The tween mechanism is performed on a target object over a period of time. For instance, zoom, resize, fade, dissolve are tween effects. So, if we create an object with its coordinates being described by an equation above and thinking of parameter t as time - it should be possible to create an object that moves according to a chosen trajectory.

Here is the implementation of all said above. (Click on the green box to start the effect).

Here is the code.

Of course there is an issue of the velocity not being constant. There is no easy way to go around it, except to choose the points spaced by approximately equal distances. Other solutions are described here.

Hope it will save someone time.

Frames

In this post I wanted to share my experience on how to make your own picture frames and do not spend too much money. The simplest frames that I built this time cost me about 1$ each. Of course they were of small size intended to be wrapped by a cloth and thus did not even require paint.

In general, the exact approach could be used to make any type of frames, theoretically of any size, shape .. etc. I used staples to put the parts together but any wood glue could be used for a better look. I used a simple rectangular wood stock but a decorative wood sticks could be used instead. Honestly, most of the pictures or arts that people are putting on their walls are not heavy and therefore simple glue would work just fine in most of the cases and no metallic brackets or parts with matching slots are really needed.

So, to start you need a simple set of tools that could be purchased in a craft store.

Tools

Here is the wood stock for the frames.

Wood Stock

Using the alignment rig and the saw I simply cut pieces of necessary length at 45° and stapled them together on both sides.

Stapling Pieces

Progress

That is it. Simple ? isn’t it?

Made Frames

And, finally, the final look with a cross-stitched art wrapped around the frames and affixed to them using same staples.

Cross Stitching

The Outcome

Last week my free time was deliberately spent on making an ordinary old fashioned bed look … how should I say?! … differently, hopefully, more unique and original. The way the bed looked when we got it from our good friends did not please my eye, quite the opposite. Therefore, my hands were free to experiment with it.

The first thing that I disliked about the bed was its height - me and my wife are not big fans of tall beds. And it is not because we are afraid of heights , it is simply because tall beds look old-fashioned and take too much space in the bedroom. Another dislike came from the fact that I can not stand the footboards - especially when my legs do not fit and I constantly kick that annoying barrier.

The Original Bed

So, keeping those concerns in mind two requirements were agreed on: 1) the bed should be less tall (as much as possible), 2) the front board should not obstruct the legs of the people who are sleeping on the bed.

The first goal was quite easy to achieve: simply, by cutting the headboard legs short. This had lowered the bedstead by more then a foot. Thus, the first goal had been achieved. Probably, the bed could be lowered even more if the box spring was either removed, or substituted with a thinner one, or somehow rebuilt. (If I ever decide to lower it more I will update this post.)

Cutting the legs off

Shortened Legs

Time for the footboard came. I started by removing the steel “grill” by unscrewing a couple of screws. Then, I removed the lath that was on the board, leaving only the outer frame intact.

Original footboard

Next, I moved the hardware that holds the bedstead together higher, by approximately a foot. Then, I cut the extra length of each of the leg off to make them of the appropriate length - so they match the headboard.

Footboard Modifications

Fortunately, the lath, that I recovered earlier from the footboard, fit nicely inside of the new design and made the new footboard look quite nice.

Footboard, New design

Finally, after the lath was affixed with screws the bedstead was assembled and the mattress with the box spring were placed on their original places. Here is the outcome.

Outcome

Ah forgot to mention … the steel grill I used to decorate the floor lamp in the corner of the bedroom.

The Grill, New Home

Result: no extra parts and materials were needed, house hold tools worked just fine - new original design for an old bed.

The Result

A couple of years ago I saw how an engraving was done on the top of the painted piece of wood by one of my friends. Since then I always wanted to try it myself. Finally, about a month ago, my trip to France gave me this opportunity as I decided to make a gift for my friends living in Burgundy.

Their family has been in the wine business for quite a long time and their wines Pouilly-Fuissé and Saint Veran produced in their Domain Du Chalet Pouilly (http://www.chaletpouilly.com) has been among my favorites for years.

First of all, I would like to say that I did not use any of the special wood carving tools that probably should have been used for this project. Instead, I used a widely available crafting knife to perform all of the cutting. I can not say much about the type of the wood suitable for this type of projects - I am not a specialist in this field after all (if someone is, please, feel free to advise). I am even not sure what type of wood I used. I simply found a piece of wood that once had been used as a martial arts target.

Preparing the Canvas

The piece of wood that was about to serve as a canvas first was cut into an appropriate shape and inspected for the sticking out chips that could easily end up under someone’s skin. Once that step was completed the piece was painted with the black acrylic paint. The choice of the color was completely up to me. Obviously, the black and white classic combination could never look wrong.

Canvas Preparation

To wrap up the preparation it was let to dry.

Preparing the Image

Before the image can appear on the canvas it has to be somehow reflected on the painted surface, for instance, in the form of some guides that may help the cutting. One way to do it, of course, is a simple pencil drawing but transferring an image in this way can require some artistic skills that not everyone possesses. Therefore, plan B comes into play - printing the image on a sheet of paper, attaching it to the canvas surface, and tracing the image with the knife making slight perpendicular to the surface cuts.

Transferring Image onto Canvas

Once done the black surface should read the original image when positioned at an angle to light.

Preparing the image from a photograph could be tricky. A typical photograph contains millions of small features that could seem very important to the whole composition. However, that is not exactly true. By tracing only some lines and shapes of the photograph the reproduced image can appear way more artistic than the original.

The way I went about it - I used GIMP (any graphic editor with layers would work just fine). I put the original photograph in the background and overlay’ed it with a transparent layer where I did all the drawing. I traced only some of the main features on the photograph and that resulted IMHO in a pretty artistic copy. Finally, I added some text and the image was done.

Original Photograph

Drawn Copy

Cutting

Unless special tools are used for cutting, the process is very simple. A first cut is done at an angle to the surface tangentially to the guides on the canvas.

Wood Cutting

The second one is done in a mirror fashion on the opposite side of the guide as shown above.

Intermediate Step 1

Intermediate Step 2

Intermediate Step 3

Wrapping Up

To finish, I coated everything with polyeurathene and attached the hardware.

The Result

Project Outcome

In this post I would like to describe how one can construct a monitor wall-mount rig. Of course, this will require some materials and some tools without which this project may become impossible to complete. However, I should say, that only simple tools are required that they or their substitutions most likely can be found almost in every household.

Another thing that is worth mentioning is that this wall mount bracket will most likely loose to its commercial brotherhood in versatility and looks. However, if one spends more time on something like that, it can be turned into something more “product” looking. On the other side, this could be necessary only if someone is very concerned with the look of something that most likely will not be seen by anyone.

Finally, for this project I needed some scrap aluminum, several nuts and bolts, and some tools.

I started with the sketch of the bracket and its functionality. (apologize for a sloppy drawing)

Sketch of the wall mount bracket

Of course, this simple bracket has only one degree of freedom but as long as the application permits it, as in my case, that is acceptable.

I started off with searching for an appropriate pieces of aluminum. Fortunately, I was able to find one already bent and of appropriate size to match the hole pattern on the back of my monitor. The second piece had to be bent.

Aluminum Scrap

Next the aluminum piece was bent to the appropriate shape and several fixing holes were drilled.

Intermediate Steps

After this I was able to see how everything was going to look and work.

Wall Mount Preview

The last step was to drill the monitor mounting holes and the holes to mount the wall bracket on the wall.

Screwing the both parts on their places I got.

Putting thing together

Hanging the monitor on the bracket.

Assembled and Hung

Finally, the last step was to put some spacer between the monitor and the wall to make sure the monitor was at the convenient angle to the wall.

The outcome of this project looks like this. Cheap, fast (~2hrs), and functional monitor wall mount.

Project Outcome

Security Tag

One day my wife’s shopping brought me not only a substantial amount of charges on our account but, as well, a little headache that the store personnel forgot to take off one of the skirts that she had purchased. Unfortunately, my wife lost the check for the skirt or did not really want to go back to the store to remove it. That made me the responsible for removing it off the skirt.

First of all DO NOT USE THIS TECHNIQUE IN YOUR WRONGDOINGS!!!! Use it only if you have purchased the item and the store personnel forgot to remove the tag. This article also applies to a simply mechanical tag that does not contain any ink and is not activated by a magnet.

Also, I did not use any hook keys in this procedure that, I am pretty sure, make opening of this lock trivial. Unfortunately, most of the time they are unavailable.

First of all, I was not sure what type of security was inside of this particular security tag. Therefore, first I tried a powerful magnet to open it. I used a magnet from a hard drive as reported to work with some of the magnetically activated security tags. This attempt failed - nothing moved. (Later I found out that this tag was not one of the magnetic ones.)

Hearing the stories that some of the security tags have ink inside I did not dare risking and forcing the pin out. Instead, I carefully started doing a “lobotomy” of the tag.

First, I cut off the top of the longest tail of the tag and found out that there was no ink in it but only a magnetic strip - the one that makes the alarm go off when you carry it through the store entrance. This operation came out to be pretty useless in opening the tag as it had not revealed any parts of the actual lock.

Security Tag, Magnetic Stripe

Then, I moved on onto cutting the rest of the top of the tag. Forgot to mention, any attempts of just prying the top off the tag with a screwdriver or a knife did not result in anything good - the housing of the tag is very strong and is glued together with the bottom very well.

Opening the Security Tag, More

After the top was removed everything became very clear. No ink .. no magnetic parts … just mechanical lock. Pressing with a screwdriver on the side of the metallic membrane opened the lock. The mechanism of this type of the security tag is pretty interesting. The security hook incorporated inside the tag prevents a simple poking with something sharp from opening the lock.

Security Tag, Mechanism

So, basically, the way the mechanism works is: the security hook (1) is being pushed away opening a passage for the main key to press on the side (2) and deflect the metallic membrane away from the pin. Simple and Brilliant!

After the tag was taken off I decided to see what would be an easy way to take this type of the tag without cutting the plastic. After several trials it seemed like drilling a hole (making it with a hot object or else ) on the side of the tag and then just using a screwdriver and such to open the lock was the easiest solution in absence of a special hook key.

Opening the Security Tag

If you know a faster way to do the same, please, share.

Purse Light

This project was a result of hard work by a group of people for “New Product Development” class competition at Georgia Institute of Technology, School of Management in Spring of 2008.

Purse illumination idea has been around for quite a while. As we found during our patent search - the oldest relevant patent was dated 1946. However, none of designs were ever adopted for mainstream markets. Our goal was to create a prototype, that could be productised later incorporating state of the art technologies. Such technologies could be represented by miniature light sources, conductive fabrics and threads, lightweight rechargeable power sources, and etc.

First of all, we identified an existing customer need by searching and participating in internet forums related to fashion. Surprisingly, our idea generated a substantial amount of interest from users of the forums.

During our patent search we understood that it would be easier to distinguish our product from other existing ones by using contemporary technologies in our design. Therefore, conductive threads use was a main focus of our project as this feature would make our product stand out due to presence of illumination seamless to the design of a bag. That in its turn would make the potential customer choose it over others

Conductive Thread

In order to identify the customer needs, we offered an online survey using resources provided by our school (however, there are tons of other similar tools available online). We received total of 214 responses. The distinction in preferences between male and female responders was apparent with, as was expected, higher level of interest from the young female responders.

Based on the results of the survey we identified our core need to be “illumination” and important features to be “aesthetics, durability, versatility, long battery life, lightness, compactness, automatic engagement”.

During the concept selection stage we considered a vast variety of light sources, power supplies, wiring options, switches. By using a generation matrix with weighted criteria and aesthetics considerations we were able to narrow down the pool of concepts to a few. These few underwent testing.

The illumination performance was assessed for different light arrangements inside a prototype purse (purchased from a local retail store).

Prototyping Purse

Hard-wired high intensity LEDs were placed on the bag’s interior with a double sided tape using different arrangements (considered quantities and locations) and the performance of each was assessed.

Light Arrangement

During the durability testing we tested how conductive threads performed during deformation/impact, exposure to fluids, heat. These tests revealed a need for use of a special sewing technique - combination of a conductive thread and a normal thread. During this sewing process the conductive thread stays to one side of the fabric that makes it invisible or non-intrusive to the interior design of a bag and, most importantly, prevents the conductive threads from forming a short in the electric circuit.

Wet Testing

Based on the selected light intensity we estimated the battery life time, previously, choosing two AAA batteries as a power source (~16 weeks of use).

Based on the knowledge acquired during previous stages we build a prototype with the following characteristics.

Prototype

The best balance between light intensity and amount of LEDs was established at 6 LEDs located by 3 on each side of the bag diagonally (two diagonals crossing when viewed from the side).

Double sewing technique to isolate conductive threads from bag compartment and prevent electric circuit shorts. (view at the reverse side of the interior fabric)

LED mounting

- LED’s and resistor are strapped under conductive thread
- Flexibility, look, and texture of inner lining is not altered

Lights and Fabric

- Low weight and size of illumination system

An automatic switch, allowing light to come on every time the bag was opened, was incorporated in our prototype by placing a magnetic switch inside the bag’s existing features.

Automatic On/Off Switch

Furthermore, a manual switch allowing to disable the illumination was placed together with the battery holder in the side compartment of the bag.

Manual Switch

Finally, a fully working prototype.

Cost Estimate

Based on this analysis we concluded that additional cost will prevent entering low price segment ($10-20), but is negligible for medium and higher priced bags ($100-5000)

Future Improvements and Steps

• Plastic caps/or custom LEDS to further incorporate the lights in the bag design
• Addition of light sensor to circuit -> lights go on only in darkness
• Addition of timer to circuit -> lights turned off after specific time interval
• Use of different LED arrangements
• Evaluation of different concepts by focus groups

by Bhavneet Binder, Sonia Agrawal, Alexander Epple, Szabolcs Palinko, Michael Parnell, Sergey Tereshko

Jigsaw Puzzle

Jigsaw puzzle is a well-known “timespending” for kids as well as for adults. Typically, this craft is considered as something that is done once and then stored somewhere from where it will be pulled out next time only during house cleaning or, even worse, moving out.

However, some people do preserve an assembled puzzle and put it in use for decoration. I would like to stress that this is a quite original and affordable way to create a decent and, most importantly, made with your own hands, art piece. It can be easily used in home decoration serving as a simple framed picture on the wall or a decorated table surface.

Spending time with your family or friends on solving it fills the result with a special meaning for those who were involved.

Modern tendencies in design dictate a necessity of having several “same family/theme” pieces aligned next to each other in some original way in order to create a uniform atmosphere in the room or on a wall. Unfortunately, the jigsaw puzzle manufacturers do not produce theme series of puzzles of sufficiently large size, that, when combined, could be a great tool for decorating walls in our homes. (At least, I have never seen one.)

However, there is hope… and this hope is in large size puzzles that could look pretty nice if framed just by themselves. In my opinion, a decent look could be achieved by choosing a large format puzzle, at least 1000 pieces, with a size bigger then 20″ (60cm). In this case, a large area art piece creates an atmosphere by itself and does not require any complementary pieces.

The choice of the aforementioned atmosphere lays completely on the shoulders of a person who designs the look of the room. A lot of the factors should be considered when choosing a puzzle to be an art piece - for instance, wall, furniture, floor or carpet colors, how lit the room is, what other art pieces are already present.

I should say, that most of the time it is very hard to make two art pieces of completely different nature look good when placed next to each other. By different nature, I refer to, for example, oil paint and photograph pictures. Most of the time such combination does not work due to their very different surface texture (rough versus smooth), and, thus, they reflect light differently. Therefore, do not try to put a painted portrait of your grandfather next to your recent photographs - choose another wall.

The process of preparing the “puzzle-based” art piece is well known:

• assemble the puzzle (nothing surprising here! right?! )
  

  Assembled Jigsaw Puzzle

• transfer it on a large piece of paper (bunch of newspapers will work. But, be careful two thick “cushion” could create a wobbly surface and the puzzle would not dry flat)
  

  Puzzle Transferred on Paper

• cover the puzzle with the puzzle saver/glue ( just follow the instructions on the can) - I would advise to use your palm instead of an included brush, as brushing, could take you hours. Contrary, just pouring the glue in a maze pattern all over the puzzle and using your palm to spread it takes at most 10 mins. But, please, make sure the glue you are using is not toxic (usually not). After, just wash your hands with soap and warm water.
  

  Applying glue to the top surface of the puzzle

• dry it, frame it. When purchasing a frame you obviously have three choices: buy an exact size frame (rarely possible); buy a smaller frame (you will have to cut the puzzle); buy a bigger frame and make it look good. I chose the last option - bought a simple and cheap frame at Walmart that was a bit bigger than the puzzle.
  

  Colored Background

  As you can see, I used the original printed sheet that comes with the frame and just flipped it. Obviously, white background did not look good, so I painted a black frame around it - so that this black frame would cover the gap between the frame and the puzzle (see insert on photograph). Next, I put the frame together and glued the frame joints with heat glue gun (very easy to re-work later). This step was specific for my type of frame - one where edges are fixed on the center piece by a tight fit and are hold by friction.

  

  Fixing Frame Corners

The advantages of creating a jigsaw puzzle art piece:

• due to its surface texture does not look like a boring printed art
• very affordable
• can serve as a memory of a get-together event
• if someone gets bored with it - just through it away and make a new one.

Here is what me and my wife created, and, later, decorated the walls with in our apartment.

Completed Project 1

Completed Project 2