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Archive | July, 2012

People Staring at Computers

I’ve dropped some hints on the site that I teach at an art school and am an artist. When Art, Apple and the Secret Service Collide: ‘People Staring at Computers’ is an article about Kyle McDonald’s media artwork People Staring at Computers that caught my eye. Of course it also helps that it has Apple and the US Secret Service are in the title.

In my view what is most interesting about this work is the way the discussion mushrooms outward and the work finds an audience. As the author says, without Apple becoming (remaining?) paranoid and calling the Secret Service, the audience for the work would have been orders of magnitude smaller.

In one sense though, the work anticipates the discussion of the work and both together become the art work. Some artists have referred to creating “social objects” as a goal of their work, and that concept (although I know some readers may find it a stretch) seems very appropriate in this case.

Another irony of the article that remains unremarked is that Apple touts itself as enabling their users to be more creative and supporting artists, and creative endeavors in general. In the real world though (as opposed to ad campaigns), creativity is unpredictable, and not always easily recognized. When faced with something not quite recognizable, most corporations are going to call their legal departments, rather than embrace it. Another artwork that comes to mind along these lines was the apartment that a group of eight artists built in our downtown mall’s parking garage. Rather than celebrating the work, and sponsoring a short exhibition before removing the work, the mall owners just destroyed the work, and legally threatened the artists.

In any case I found this an interesting read. It also explains why the people in the photograph above are wearing Steve Jobs’ head.

Pulse Sensor III: Heart Rate Variability

Ways to limit the sources of noise

Where does the noise come from in the Modern Device Pulse / PSO2 sensor? I’ll make a list of some of the places I think noise comes from. Some of these will be supported by experiments to get rid of the noise and others will remain more speculative. The SI1143 chip in the PSO2 sensor uses a photodiode and an amplifier, to amplify the voltage for sampling by an A to D converter.

Sampling on the power line frequency

In my experience, anytime you use an analog amplifier at medium to high gain, in a an indoor environment that contains power lines, the possibility of power-line hum being induced onto your signal has a good probability. This is true even if the devices are powered by batteries – such as a laptop. The field is so pervasive that any nearby amplifier will capacitively couple with it at some level.

One classic way to minimize this power-line noise is to sample on the power-line frequency. This insures that any sixty cycle signal impressed upon on the desired signal is averaged out. It is simple and easy but comes with one very large drawback, it is slow. A power line cycle in the US is 16.666 ms which in terms of a computer’s speed, is basically forever (266,666 Arduino clock cycles for example). Luckily for us, in terms of a human heartbeat, 60 hz is still fairly fast and a human heartbeat sampled at 60 hz or even 30 hz still looks great.

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