alex menezes' final project journal

itp/ nyu

U Blend - A blender’s pulse controlled by a human heart.

The idea

The initial idea from this project was to use a biological function as the input for a physical computing project. Two things were important, to have an amplification effect, transforming this secluded function into something public and visible, and a nonsense factor, associating the biological function to a completely unrelated mechanical object. This project focuses on the heartbeat because of its symbolic (and quite concrete) importance, often representing life in itself. The heartbeat blends here with a very simple machine, an everyday appliance, controlling it and giving it life. This unusual blending produces an uncanny effect, in which organic and mechanic/ electronic forms are progressively becoming more indistinct. Very small plastic baby dolls represent the material that will be blended inside the device, they are accompanied by a few computer silicon microchips, bringing into the blender’s cup the metaphor of combining biology and machine. When pulsing, the blender shakes and moves rhythmically what is inside, but does not destroy its content.

Materials

To build this object I have used a few products and materials from different sources. Here is a description of them:

Heartbeat Sensor: Since my midterm project I have been exploring the possibility of using a heartbeat sensor. Because I wanted something that would sit inside an object and provide a reading just from finger touching, I have decided for one of the models that needs to be touched by the tip of the finger in order to read the heart pulse. This kind of sensor is not very accurate, though, when it is used during intense physical activity and it is recommended that the user stands still before actually using the device. For the purpose of this project this was not a problem, because the final object would not be moving around.

The original device is quite inexpensive, and is widely available for online order. The device I used is called ‘Pedometer with Pulsemeter’, and it is manufactured by Oregon Scientific, the model # is PE316PM. I also chose this model because it was recommended by other students from ITP that had done a heartbeat sensor project during the previous semester. As it turned out this product is quite useful in terms of producing a clear signal that can be read by the BX, but it is very fragile and should be hacked carefully.

A few useful lessons learned from hacking this product:

-         Some extremely small parts easily fall out as you open the device.

-         Because the device is not only a pulsemeter, in fact its main function is as a pedometer, it has a button that activates the heartbeat sensor. I had two wires soldered to the circuit board in order to be able to activate this function from outside of the device. In my final project the reset button activates this function.

-         In the original Oregon Scientific product there is a small black piece of elastic fabric that covers the sensor and creates a suitable slot for the user’s finger. In this project I needed the sensor to be as discrete as possible in the body of the blender, and decided to not use this type of covering. This was not a very good idea. Apparently the infra-red sensor needs to be protected from direct light and this exposure will lead it to break. I got this advice from Max Amigliani, the ITP student that has used this product previously. Unfortunately I only heard this after I had already hacked the device and had it exposed to light for several weeks. Eventually it stopped working, and I am not sure if it was due to this, but it I will be more cautious next time.  

-         The signal from the device is a voltage variation that that can be input to the BX trough ‘Analog to Digital Conversion’. Although it is not exactly like a heartbeat, there is quite a rhythmic interval that can be converted into pulsing. There is a specific chip opposite to the heartbeat sensor, on the same circuit board that can be used for getting the signal.  The wire should be soldered on the first pin, from left to right.

   Reset wires                    The sensor               Wire on the first pin             The hacked device

Blender: A conventional blender with a black base and a convenient push button for the pulse function. I used a ‘NuBlend’ brand blender. Its plain design suited the purpose of the project and the push button slot matched the size of the infra-red sensor I was using, allowing this small hardware to be inside the blender and be touched from the outside. I disassembled it by taking off the motor cover. I also decided (Following Jen’s advice) I did not want to deal with all the high voltage wires inside the blender so I just extended the pulse push button wires, that were quite easily visible, removing the button from its original location. This also allowed me to turn the blender on from outside. I drilled some holes in the Blender’s base, allowing wires to pass to the box that contained the BX and the reset button.

I did not want the blades in the Blender to actually cut the objects I was putting inside. The effect I wanted to obtain just needed the blades to turn the objects in rhythmic fashion. Therefore I covered the blades with epoxy, completely neutralizing the cutting edges, while still leaving space for it to move.

Servo Motor: Because the blender works on AC and the BX on DC, I was unable to turn the first by using a transistor linked to the BX. Jen suggested that I used a servo motor to act as a switch. The servo would be controlled by the BX, and it would move to trigger the blender without ever linking electrically both devices. This is a simple and convenient way to do this. The servo needs another source of power, different from the BX, so I used a 9 V battery to power it. The programming for the servo motor was quite uncomplicated, I got the original code from the physical computing website and made small changes tuning it to fit the kind of movement I needed. Please refer to the code section for the exact program I used.

Wooden Box: A wooden box functioned as a base for the blender and also as a container for the BX, the servo motor, the reset button, and the power sources for the BX and the blender. I had the different pieces of wood that constitute the box cut to size at Home Depot. After sanding these pieces of wood for a smoother effect I glued them together using wood glue. The next day I nailed them together for extra resistance.

I wanted the box to have a function rather than be just a container, therefore I decided to paint it with chalkboard paint. I got the Paint from ‘Cite’ (100 Wooster St.) in Soho. Using this paint I was able to have a black finishing that matched the blender and it also allowed me to create a surface for writing content related to the project.

Inside the cup: Inside the cup, representing human life, I had small plastic babies. They are sold by the scoop at a design store called ‘Cite’ (100 Wooster St.). I also bought an old computer floppy drive and extracted some silicon chips to increase the texture contrast and reinforce the metaphor of blending organic forms and machinery.

Putting it all together

1-     Hacking the heart sensor: I opened the device and started to test the circuit board to locate power, ground and the heart signal I needed. Jen was very helpful in doing this, we used a voltmeter. Once I had found the connections that were relevant to the project I started to solder them, again with Jen’s help, since the little pins and contact surfaces on the circuit board requested a very precise work, and my shaking hands and limited soldering experience would not do it. We also soldered two wires to each of the ends of the reset button, allowing to trigger this function by connecting the wires.

2-     Once the wires were soldered, I connected them to the breadboard in which I had the BX. 4 wires were relevant: the one with the signal from the heart sensor, ground, (to link it to the same ground of the BX) and the two reset button wires. While I was testing I had them connected to a small reset button on the breadboard. When the project was finalized I connected them directly to a pushbutton on the lid of my wooden box.

3-     I tested extensively the input signal, converting the analog voltage variation into digitalized numbers. There was a quite constant pattern when the sensor was on that involved an up curve followed by a down curve. Based on the numbers I was getting, I chose a trigger (around 450), above which the blender would be turned on. I tested this trigger, using different people and an LED as the output. Although this was not precisely the heartbeat frequency, it did have some rhythmic variation that could be easily related to the heart frequency.  

4-     I then had the blender prepared. I first opened it, removed the pulse pushbutton, and the rubber cover on it, so that the sensor could be placed on this slot, inside the blender. I extended the wires on this pushbutton, in order to allow me to trigger the blender from within the box that would be beneath it.

5-     I had the box made and painted. The next day I started the assembling process. I made a hole on the lid to fit the pushbutton switch (from Radio Shack) that would be the reset button. I used mounting tape to hold the breadboard and all the other devices on the base of the box. I used a screw to keep the blender base attached to the box lid. Once it was in place, I made a few holes in the box, under the blender, so that the wires would be able to go directly inside the box.

6-     I fixed the servomotor and the switch to the inside walls of the box. I did this in a corner so that it would be easy to have one touch the other. I then tuned the BX programming for the servo function, creating the exact movement I wanted.

7-     I placed the Sensor inside the blender, using electric tape and some “Tac’n Stik” brand reusable adhesive to hold it in place. I connected the wires in a way that they would be long enough to reach the BX, placed in the box.

8-     I wired the reset switch from the sensor to the pushbutton on the lid of the box.

9-     After that, I connected the wires that originated at the sensor to the breadboard. I put the lid on and, connected the power sources and was ready to go.

10- The last touch was to add some water inside the blender’s cup for a more interesting mixing effect.

But...

At the last minute my heartbeat sensor crashed, and would not give me any signal. Unfortunately, my project was not working, although everything was ready to go and connected correctly. I retested it many times, but finally had to give up. I will take a break from it and after a few weeks I will dive again into the heartbeat sensor world and re-do it. If I make any progress I will post the updates to this page.

 Click here to access the code used to program the BX-24

Picture Gallery

  reset button               the final thing              Wiring