Tuesday, 20 November 2012

Research and Development - Sensors and experimentation with installation

I researched what sensors where and how they worked but it ended up being very broad since their is so many different kind of sensors and how they worked. Heres the general discription of a sensor and to explain how it works.


A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards.
Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.
A sensor is a device which receives and responds to a signal when touched. A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. For instance, if the mercury in a thermometer moves 1 cm when the temperature changes by 1 °C, the sensitivity is 1 cm/°C (it is basically the slope Dy/Dx assuming a linear characteristic). Sensors that measure very small changes must have very high sensitivities. Sensors also have an impact on what they measure; for instance, a room temperature thermometer inserted into a hot cup of liquid cools the liquid while the liquid heats the thermometer. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a microscopic scale as microsensors using MEMS technology. In most cases, a microsensor reaches a significantly higher speed and sensitivity compared with macroscopic approaches.

But for the type of method I want to do because my sensor will be inside/under a chair and I want it to activate when it its pressed. It was suggested that a pressure sensor would be my best bet and the right one to go about doing.

Pressure Sensor

A pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of the pressure imposed. For the purposes of this article, such a signal is electrical.
Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude. Pressure sensors can alternatively be called pressure transducers, pressure transmitters, pressure senders, pressure indicators and piezometers, manometers, among other names.
Pressure sensors can vary drastically in technology, design, performance, application suitability and cost. A conservative estimate would be that there may be over 50 technologies and at least 300 companies making pressure sensors worldwide.
There is also a category of pressure sensors that are designed to measure in a dynamic mode for capturing very high speed changes in pressure. Example applications for this type of sensor would be in the measuring of combustion pressure in an engine cylinder or in a gas turbine. These sensors are commonly manufactured out of piezoelectric materials such as quartz.
Some pressure sensors, such as those found in some traffic enforcement cameras, function in a binary (on/off) manner, i.e., when pressure is applied to a pressure sensor, the sensor acts to complete or break an electrical circuit. These types of sensors are also known as a pressure switch.

So been looking into different ways about how to create this type of sensor and what other materials I would need to make it work since money and time is limited. I researched different methods and tutorials on how to create the sensor and found some really useful ones on youtube. Theirs all sorts of different ways to go about creating the sensor from easy to really complicated ways.

 These are just some examples but ended up finding this one the most useful down below.

Since it was really simple to make and was made out of everyday items you find round the house. 
After finding out how to create a pressure pad I had to look into what other equipment was needed to for the sound. It turned out we had some speakers lying around in the flat from the previous flat owners who were friends and didnt want them anymore.

With help from Alastair who was happy to assist me and used to play around with eletronics as a kid and had every wire known to man.
(go figure)
Explained to me and showed me how the process could be done and what was right equipment.
We experimented with the different types of speakers first to see how the sound piece sounded through them since it sounded fine with headphones. We used a AV switch as an extender to from the laptop and then to the speakers with a button control also. We had trouble with the speakers since they were mostly bass speakers and sometimes one would cut out. We opened it up and tried to fix it on the inside but it didnt seem to help. We tried another set of speakers but had problems then with the sound quality and of the piece being in Mono instead of Stereo.

After that not working out so great and spending till 3.00 in the morning trying to get it to work in every way we thought possible. Decided the best thing to do was to hunt for some new cheap speakers the next day. Ended up finding a small descent set that had different connections and pretty good sound quality.
We also got a audio jack extender from poundland which came in super handy.

We then began to create the pressure pad following the tutorial on YouTube.

We used tinfoil, cardboard, foam, normal tape, and then cut the middle of the audio jack extenders wire to expose the circuit. We then transfered my sound piece onto a mp3 player I brought from home incase it could be useful. And then it took a while but we tried all these different wire combinations to get the right circuit balance. A lot of strange things happened such as sometimes the sound would only work in one ear and then next only the bass could be heard. It was really strange and different each time the quality of sound trying to get it to work.
One time the sound did'nt work until we turned the pressure pad upside down very weird!

Eventually we found the right combination of wires and linked it all up to the speakers and mp3 player. I can also play my sound track on loop with the mp3 player which is what I wanted for the sound installation.

The pressure pad works really well but is a little fragile but it does work and we even tried sitting on it. The effect of the stereo also works quite well with the speakers. But now I have to try and get it to work in a space in the university and record the process. This will be my next step as well as continueing with sketchbooks and the rest of the blog posts.

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