(click images for better view)
A blend of technology and art, this is not just any
blinking light. The Picaxe microcontroller constantly records room
temperature as detected by the DS18B20 onewire temperature sensor.
An array of recently recorded temperatures is used to determine
the minimum and maximum values over the last few minutes. From this,
the most recent value is autoscaled and the bi-color LED eyes pulsate
with an indicative color somewhere between green (coolest) and red
To make the sculpture more interesting (both electronically, and
to the viewer), the LEDs are also used for continuous detection
of ambient light. You read that right... In addition to generating
light in this circuit, the LEDs are also used to sense light. When
the detected light change is above a threshold, the sculpture pulsates
faster and uses a smaller recorded temperature array. Shade the
eyes for a second and the sculpture starts pulsating at 1 second
intervals. Now the viewer can easily control the eye color by heating
or cooling the temperature sensor slightly by simply blowing on
it or touching it. A 0.1 degree change is sufficient to make the
complete eye color transition. After a period of disuse, the blinking
slows back down to a slower rate (approx once every 15 seconds)
to preserve battery power.
The robot body is constructed of old UV sensitive EPROMS with a
really nice clear-windowed chip for the thorax. Viewers usually
don’t appreciate the layers of engineering which allow something
like this to be built (e.g. digital logic, microcontrollers, ADCs,
etc.). However, I’ve been told that the sculpture body is
cute (well, cuter than a real robot)
and the fact that the eye color actually means
something is icing on the cake. Explaining that the sculpture is
in-circuit programmable hasn’t been worth the hassle except
to the EE minded, since the shock and awe of a blinking light on
a humanoid shaped body usually seems sufficient.
Power is supplied by 2 rechargeable AA’s which are constantly
charging via a small 3.6V solar cell supported by connecting wire;
simple but adequate. Who wants to have to change batteries in a
Picaxe 08M microcontroller
DS18B20 temperature sensor
3-Lead Bi-color LEDs (2)
220K resistors (2) - to current limit the LEDs
3 pin programming header
AAAx2 battery holder
AAA NiMH battery (2)
3.6v solar cell
The thing I love about these picaxe projects is that the design
and assembly is pretty minimalist. As the schematic
shows, just hook the bi-color LEDs and the DS18B20 to the Picaxe,
program the chip, and you're done. Use your imagination for the
body. Old computer ICs hotglued together in any configuration could
for this sculpture is fairly straightforward. Recording a continuous
loop of data in such a limited chip took a bit of planning. Code
memory is pretty limited, so I find myself constantly rewriting
bits of code in order to squeeze just one more feature into the
device. Since software allows for infinite flexibility, coding is
never complete; it just reaches ever higher plateaus of acceptability.
software uses the same circuit for a slightly different behavior.
It pulses a random color between red and green, and occasionally
indicates the temperature in morse-code encoded flashing.
This code is explicitly released under the GPL.
And this page is licensed under a Creative
Commons Attribution 2.5 License.
Write me if you find this project
interesting. Link to this page if you find it relevant.
Warning, warmly greet new renewably powered interactive autonomous
electromechanical overlords. This project is provided without any
warranty and probably isn't suitable for anything.
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