Servo Pointer Project
In this project I build a medium sized gauge using FoamCore for the triangular pointer and a matching base. I used a model airplane servo motor to turn the pointer, which I held together with DoubleStickFoam. I freehand cut the pointer to get a more funky look. I guided my xacto knife with a steel straight edge for the rest of the cuts so the base would fit nicely and hold with hot melt glue.
Tip: I eyeballed all the angles, trying not to have anything square and boreing. However, I made sure that the two back braces were cut at the same slope by just dividing a square board at a slight angle.
I used the ServoMotor program to run the pointer off of Bynase levels. I tested with the AnalogKnobConverter producing the signal.
Knob -> ServoThe full range of motion of the knob (270 degrees maybe) was larger than the full range of motion of my motor (180 degrees or less) so the pointer had a feeling of being slow.
I reconfigured my AnalogKnobConverter as a light sensor. Then I started having fun.
Sensor -> ServoThe pointer would sit quietly pointing in a positive direction as I worked, only to surprise me when my hands cast a shadow over the sensor and the pointer sprung to life. Turning off the desk lamp confirmed that, yes, that made it even darker.
When I tired of waving my hands and watching my pointer wave back in unison, I got the idea of having the pointer wave over the light sensor and thereby creating a FeedbackLoop.
The pointer was big enough to cast a good shadow. When this touched the sensor, its output fell, the pointer moved, and desk lamp light returned to the sensor. I moved it further, the same thing happend. I pulled back. The pointer moved the other way, to cast its shadow on the edge of the sensor.
The two sides of the shadow worked differently. This reversed when I flipped the pointer over so the shadow drove the pointer the other way.
I found that by adjusting how close to the sensor I held the pointer I could change the sharpness of the shadow and thereby the quickness (or gain) of the feedback. When I held it with a half-inch, the system over responded each way. This oscillation continued, with an amplitude of several sensor diameters, even as I repositioned the pointer as I had been doing before.
I tried adding a FilterTransform to the Bynase circuit.
Sensor -> Filter -> ServoThis changed the frequency of oscillation, but not the amplitude or threshold.
I've yet to connect my gauge to anything happening on my home or office network. For this I think I would use a script on a big computer to run queries and send results, probably as a single character, to a Bynase enabled computer programed to listen.
|Last edited March 11, 2006
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