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Little Box : Tray

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The tray is an important element to the box. It needs to be elevated and flush with the top of the box and also allow the actuators to pass through, lifting the lid. To bring the tray up making it flush with the box we cut clear, square acrylic rod to the height of the box less the material thickness of the Corian. We placed the risers in each corner as supports and the tray rests neatly on them and flush with the exterior box.

We needed to make holes for the actuators to emerge through when lifting the lid.  This was a nerve wracking part of the process, as we only had one chance to make the holes.  Because there was a small tolerance around the border of the lid and because the actuators were elevated slightly above the height to allow the tray to sit flush, we could not use any pattern for making these holes. Our measurements and precaution served us well, though, and our holes were perfect.  

We used a 3/8″ drill bit which was slightly wider than the diameter of the rod. Drilling through Corian is relatively easy, but you must drill from the top-side downward because there are small chips on the back side of the drilled hole. 

 

 

 

 

 

 

 

 

Little box was commisioned by Harvestworks with funds from the New York State Council on the Arts supported by Governor Andrew Cuomo and the New York State Legislature.

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Little Box : Sound

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We attached speakers to the underside of the box for the sound to emanate from.  Merche Blasco is creating the sound for the piece.  Two speakers that are small enough to fit under the box have been attached and connected to an Arduino Wave Shield.  After testing speakers inside the box, we knew that we needed to keep the speakers outside of the box.  The inner tray severely dampened the noise making it nearly impossible to hear any range of sound.  While this is good to soften the noise of the actuators, it will not work for sound intended to be heard. 

We found very small speakers which we bolted to the bottom with rubber washers so they would not vibrate against the base of the box.  The wires run through a hole and directly into the microcontroller.  

The effect of having the speakers beneath the box feels like the sound is coming from off in the distance.

Sound by Merche Blasco.

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Little Box : Sensing

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We are using four of the Maxbotic EZ-1 Sonar sensors, which turned out to not be so “easy” when using more than one sensor. The sensors send out a sonar which bounces off an object allowing a distance calculation to be returned. There is a good tutorial for getting started with the sensor on Adafruit, but we needed a bit more functionality.

We wired the sensors as shown below communicating between the sensors with RX/TX. The pdf instructions of the image below can be found here. 

The hurdle we had to overcome with the sensors is because of the sonar. When the sensors are pointed in the same direction, they create noise and interference if they are triggered at the same time because one sensor picks up the sonar from another. We solved this issue by daisy chaining the sensors together and triggering them at different times. This way, each sensor would get an accurate reading without interfering with the signal from the other sensors.

 We embedded the sensors into the legs to make them as discrete as possible.  The sensor does not see the box or the table since they are close to the edge.  We drilled holes through the bottom of the box and ran the wires up inside so they would be hidden from view. 

 

 

 

 

 We’ve painted the sensors so that they blend in further, using a combination of metallic silver and black enamel.  

 

 

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Little Box : Metal Legs

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To make the sensor looks as intentional as possible we discussed placing the sensors underneath the box, rather than drilling a hole into the box.  To place the sensors underneath the box we needed to create legs which would elevate the box up high enough for our sensors to fit. We purchased the square tube shown below and cut slivers down to size for our legs.  

 

 

 

 

 

 

 

 

 

 

 We attached the legs to the base of the box with Plastic Weld 2-part epoxy.  It’s not a pretty epoxy, but it’s extremely secure. We drilled holes in the two front legs and embedded the sensors within the tube. The back legs do not have holes in them because they do not house sensors. 

Here the legs are shown with the sensors embedded, which will be described more in later posts. 

 

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Little Box : LED Wiring

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We are working with the LED Strip lights which come 60/meter and were purchased from Adafruit. These LEDs are Non-Addressable but can be cut every 3 LEDs. We purchase 15 meters and used them throughout the box.

Although the LEDs can be cut every 3, the provided soldering pads are very sensitive and can be ruined with too much heat, during de-soldering, or if cut improperly. We were aware of this before we soldered, so we wanted to create a system which would minimize the stress on the solder point. We came up with the solution to use header pins and pcb board. This way we could solder up all the pins for the lights, make the LEDs removable, and also make them secure. This minimized the amount of time the head was touching the LED strip, which ensured that we weren’t burning the connection.

The process for soldering is outlined below:

1) Cut, stip and bend the wires to length. You’ll need a wire for each color and for the +12V power input

 

 

 

 

 

 

2) Place the header pins through the PCB board and solder the connections accordingly. We noticed in our strip that Adafruit had the call outs for the colors switched, so the Green was the Blue and vice versa. Be sure to check your strand.

 

We selected headers which have an approximately 90 degree bend to them so as not to create shadows. We glued our PCB board to a plate so that it could be removable in our system and also laser cut risers to elevate the lights off the base of the box. This will also provide space for us to hide the electronics underneath the riser without interfering with the lighting. 

3) Lay down your LED strips cut to length. In our case we needed 5 sets of 3, or 15 LEDs per strand. Solder between the headers and the pads provided on the strip. Be careful not to apply too much heat too or you could damage the 3 LEDs closest to the solder point.

 

 

 

 

 

 

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Little Box : Actuator Housing

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To house the actuators within the box we knew we needed to create a cage that would secure the actuators in place without vibration and also allow the actuators to be removable in case, for some reason, they broke. We came up with a “cage” that would be partly secured to the back of the box with a housing around the actuators themselves.

We first created housing for the actuators themselves. Here you can see we left room in the housing for the motor to remain open, which helped with overheating issues, but also allowed the wires to be free. We created holes for a bolt to slide through and secure the actuator to the housing.

These pieces slip into a cage that was glued into the back of the box. The cages were elevated to get the actuators flush with the bottom of the tray. We dropped them down 1/16 of an inch below the bottom so that we weren’t resting the weight of the tray on the actuator housing.

 

 

 

 

 

 

 

 

 

 

They are secured in place with a nut and bolt and have wood to help dampen any noise from vibration.

 

 

 

 

 

 

 

The drawing for laser cutting all these pieces is below. We used 1/4″ clear acrylic to so as to minimize the shadows created by the housing.

 

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Little Box : Hinge

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We purchased a stainless steel hinge from McMaster-Carr and installed it on the box after receiving the corrected tray. We chose not to get the hinge with premade holes as we will decide where the holes and bolts should be when we position the hinge.

 

 

 

 

 

 

 

The hinge can be cut with a miter box and a saw. We made it the entire length of the box to ensure that we had as much surface area to work with for attaching the hinge to both the lid and the base of the box. Holes and bolts will be added later to create a mechanical connection

 We drilled 2 holes through the top and bottom of the hinge and adhered them mechanically with bolts and nuts.  The bols on the bottom are hidden by the tray. 

 

 

 

 

 

 

 

 

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Little Box : Corian Box Received

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We received the box back from Corian today.

Although the exterior looked beautiful, we immediately realized that the inner tray was made entirely out of the non-illumination series. We specified the bottom of the inner tray to made out of the illumination series. We also noticed a large tolerance around the outer edge of the tray.


If left as is, this would mean that the components inside would be visible and that light would seep out. We had to talk with the Corian team to return the tray and have it remade.

 

 

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Little Box : Linear Actuator Test

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After exploring many different methods for lifting the box lid, we decided that using linear actuators will be the best way to move forward. We avoided this option earlier because the actuators are more expensive than gears and motors, but they will be more quiet and better integrated into the system.

We’ve chosen a miniature linear actuator by Firgelli. We need the L-12i series which has an internal controller. The specs for the actuator are: 100mm stroke | 6V power input | 100 gear ratio also known as “6,100,100,i.” The link to download the data sheet is here.

Below is a video of our first tests with the actuators. This is using them just as an on/off switch and not incorporating the feedback control.

 

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Little Box : Corian Technical Drawings

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Below are drawings that were submitted to the Corian Fabrication house, Evans & Paul.  We had the box fabricated in house at Corian because the material is difficult to work with.  It can not be laser cut with most lasers because it tends to bend and melt before cutting, you can not create a thread when drilling through it, and gluing pieces of Corian together requires a special glue that is in essence a liquid Corian.

Drawings submitted to Corian

We specified a 1/4″ thickness. The exterior of the box and base of the inner tray are made of the ‘Glacier Ice – Illumination Series” Corian. All of these surfaces were called out in Gray. The walls of the inner tray and the flush top of the inner tray are made of ‘Glacier White, Non-Illumination Series.’ These surfaces were called out in pink.

When we first received the box back, the tray was made entirely out of the non-illumination series. It also had a 1/16″ gap between around the edge so the surfaces were not flush. We had to return the tray to get both of these issues corrected.

We received shop drawing back from the production team, which are below.

 

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Little Box Videos

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Little Box : Open/Close Animation

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The first prototype for Little Box project was building a system that can open a box seamlessly. This is a main step for the box and most of the next steps will be shaped according to our solution for this problem.

We needed to make this system seamless, with low noise and small parts. We started with ordering these parts

Stepper Motors from Sparkfun.com (http://www.sparkfun.com/products/9238)


Steel Plain Bore 14-1/2 Degree Spur Gear, 24 Pitch, 12 Teeth, 0.5″ Pitch Diameter, 1/4″ Bore from mcmaster.com (http://www.mcmaster.com/#catalog/118/1070/=gljjtx)

Steel 14-1/2 Degree Pressure Angle Gear Rack, 24 Pitch, 1/4″ Face Width, 1/4″ H Overall, 2′ Length from mcmaster.com (http://www.mcmaster.com/#catalog/118/1070/=gljkky)


Other than these we used an Arduino Uno microcontroller (arduino.cc)

We tried all of these parts with different setups and materials. Since we are pushing the lid very close to the hinges, some of these materials were not able to handle the force that we needed or they were very noisy, such as servo motors.

We ended up using 2 steppers on both sides of the back of the box and steel plain bore 14-1/2 degree spur gear. We also made our own gears for stepper motors to drive this geared rod.

While figuring out the materials it is very important to keep in mind physical laws. We ended up using torque equation. You can find more details in this page (http://hyperphysics.phy-astr.gsu.edu/hbase/extms.html)

Firstly we calculated how much force we are applying to the lid. Our stepper motors holding torque is 2.3kg*cm and our gears radius is 0.5cm. So if we multiply these 2 variables our force is 1.15 kg. This means if we position our set up very close to the lid, lets say the distance is 2 cm, and the weight of the lid is 0.45 kg, we can push the lid and make it rotate from the hinge.
1.15 kg * 2cm  > 0.45kg * 5cm(center of gravity for the lid)
2.30kg*cm > 2.25kg*cm
Also, since we used 2 motors to push from both left and right side of the lid, we multiplied our force by 2. (These calculations are estimated, and we didn’t factor in forces like friction).

As a result, if we need to increase the weight of the lid and decrease the distance from the hinge, we need to make more specific calculations and find a motor with more torque.

Also, we accomplished some extra steps and we add more materials in to the box. We used a strip of RGB Leds (http://www.adafruit.com/products/346)

and sonar sensors (http://www.sparkfun.com/products/9491)

This first prototype serves as proof of concept. Next steps will be deciding on materials, figuring out motor torque accordingly and lowering the noise as much as possible.

As for the materials, the original choice was to use Corian.  After receiving some samples of the material we realized that it’s very heavy and might not be an appropriate material for this application, unless we choose to go with a much larger motor.  This could mean that we’d get more sound, though, so we have to balance aesthetics with mechanics and physics.

Here are some pictures and videos from our set up:

          

 

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Little Box : Mechanics Development

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After testing out the bevel gears, we realized that we could not get the pivot point of the lid close enough to the back of the box. If we wanted to integrate the rod into the back of the box, we would need to create a false compartment within the lid.

We’ve decided to move forward with servos and rack and pinion gears (see below). A more detailed description will follow in later posts.

 

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Little Box : Initial Brainstorming for Mechanics

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We are looking into using beveled gears to raise the lid of the box. We think this will be an efficient and seamless way to lift the lid.

Our rough sketches, shown below, involve a servo and 2 beveled gears. One will be attached to the servo, the other will be attached to a rod that runs along the back of the box. The rod will be attached to the lid with a hinge or flange.

 

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Little Box Sketches

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Lilypad, Bluetooth and first lectures

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In order to be able to have the first lectures of the sensors incorporated we started building our first wearable bracelet with the two sensors incorporated. We incorporated a Lilypad Arduino simple board and we connected the GSR and the Temperature sensor to two different analog inputs of the board.

We did several tests with the two temperature sensors and we noticed that the first one we tried was reacting faster to small changes which seemed more appropriate to our final goal, so we chose that one.

Here are some images of the process:

 In order to be able to do long term lectures, and getting a step closer to the final prototype, the bracelet had to communicate wireless with the application that would save the data collected. So the next thing we worked on was bluetooth + lilypad. After several issues with the battery and the bluetooth system itself we got them working together. We used the Bluetooth Mate Gold modem.

 With all these components mounted together we have been wearing the bracelet and collecting DATA that we can pass to the other members of the team. We are working also on the application for visualizing the text files with all the DATA.

This is an screenshot of the visualization running:

The next step would be linking the bracelet with an Android where we can store the lectures collected in any type of situation, far from the computer.

 

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GSR and skin temperature

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According to the last results we had, we started working on a wearable prototype that could give us more stable lectures of the different sensors. We used for that one of those “tennis bracelets”.

We first incorporated two stripes of stretch conductive fabric to measure the GSR. We could see it working by adding some water on our skin and observe the different values, but it was tough to prove a secretion of sweat in the conditions where we were doing the tests. In this direction we both agreed we needed to incorporate ASAP a bluetooth transmitor and a phone that could collect the data. This way we could measure situations closer to a real scenario.

It was helpful having incorporated a way to visualize the results in Processing, in comparison of last time.

We tried then a temperature sensor more accurate than the one we used last time, recommended by Eric Rosenthal in ITP: the LM34 . According to the datasheet this component is sensitive to changes of ±½°F  at room temperature. We tested it working properly but again it was difficult to witness a change of our skin temperature in those conditions.

Here are some pictures of both sensors incorporated to the bracelet:

Measuring GSR from the bracelet

Conductive stripes and LM34

We encountered some problems with the heart rate measurements, which point to be the hardest ones to measure from the wrist. We tried to incorporate the pulse sensor we used previously taking the measures this time form the top of the wrist and amplifying the output signal, but it did not work. Afterwards we noticed that the Opamp we were using from Sparkfun had two Capacitors that were blocking the DC lectures. The amplifier was designed to amplify AC signals, so this could cause that we couldn’t get any lecture at all going through it.

Eric suggested to try with a stretch sensor tied to the wrist but getting any conclusion or rythmical pattern out of the results seems barely impossible. Here is the image of this test:

Stretch sensor measurements visualized in Processing

Redesigning the amplifier circuit of Sparkfun and testing it again with the pulse sensor could give us some options then.

Finally we decided that it would be more efficient to start measuring Temperature and GSR in real situations while we work in parallel on a way to get the heart beat from the wrist, or maybe incorporating that one from the finger while we find a better solution.

 

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Working on the first prototype – Day one

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Today we started doing some tests with the components we ordered to monitor:

– Heart rate

– Skin Temperature

For the heart-rate we did some tests with the pulse sensor ordered online and created by Joel Murphy and Yury Gitman.

It was pretty straightforward to plug and play. It seemed to read our pulse through our fingertip but it was not as stable as we expected and it did not really  work for the measurements in the wrist. We did not have the velcro they recommend to do the tests so we will try again next time to figure out if we can get better results this way.

Here some images:

Pulse sensor connected to the arduino

 

Processing application that runs with the sensor

We also tried with the infrared LED and the Light Intensity to frequency IC . We got some mesurements from the wrist but they were pretty unstable too. Building a proper encapsulation weareable could improve the results considerably, so this will be our next step on this side.

The LED and the IC are taped around the wrist pointing to the veins

 

For our last test to measure skin temperature we used a Thermistor  connected to the arduino:

and again we got some coherent measurements but pretty unstable.

For the future we will have to:

– Create better containers for all the sensors

– Average the lectures to have more coherent results

– Create visualizations to get more readable results and get conclusions faster

 

 

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