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Step 4Building the sensor turret
As you may have noticed, The Redpointer actually has two laser turrets. One of these, the sensor turret, is for inputting information into the Arduino. The other turret, the servo turret, is for outputting that recorded information as the motion of a laser pointer. Both turrets are glued to a plank of scrap wood. Here's roughly how I constructed the sensor turret.
I'm not going to go into a lot of detail here, because the decisions regarding the sizes and shapes of the bits of wood I used were largely arbitrary. Most of the curves ended up the size they are because that meant I could easily draw them using a CD as a stencil.
The most important thing to understand is that the sensor turret is made using two linear potentiometers as a pair of perpendicular axles. As the user moves the laser pointer around, rotating it on its x and y axes, the pointer rotates on the two axles and changes the resistance of the potentiometers. The Arduino measures this resistance and uses it to calculate the angle of the pointer.
One of the potentiometers lies horizontally with its shaft suspended between two fixed pieces of wood, able to rotate freely.
The shaft is attached by superglue to a third piece of wood (shaped like a truncated circle) which is sandwiched between the first two pieces of wood. As this almost-circular piece rotates between its neighbours, the potentiometer shaft will rotate with it and inform the Arduino about the elevation of the laser pointer.
The base of the potentiometer is anchored to The Redpointer's base by a section of tongue depressor glued to another piece of wood.
Notice the little semicircular notch cut into the flat top of the middle piece of wood. There is a hole drilled down at the base of that notch just wide enough for a potentiometer's shaft to fit inside. The second potentiometer is eventually glued into that hole, but first it is attached to another tongue depressor. Two CDs act as a bearing between the wooden block and the tongue depressor. Once the potentiometer is glued in place, it acts as a sensor for the laser pointer's lateral rotation.
With the two-axis base assembled, a simple gun-like handle (made from three pieces of glued wood) is attached to the top. This will allow for simple one- or two-handed control of the sensor turret.
I'm not going to go into a lot of detail here, because the decisions regarding the sizes and shapes of the bits of wood I used were largely arbitrary. Most of the curves ended up the size they are because that meant I could easily draw them using a CD as a stencil.
The most important thing to understand is that the sensor turret is made using two linear potentiometers as a pair of perpendicular axles. As the user moves the laser pointer around, rotating it on its x and y axes, the pointer rotates on the two axles and changes the resistance of the potentiometers. The Arduino measures this resistance and uses it to calculate the angle of the pointer.
One of the potentiometers lies horizontally with its shaft suspended between two fixed pieces of wood, able to rotate freely.
The shaft is attached by superglue to a third piece of wood (shaped like a truncated circle) which is sandwiched between the first two pieces of wood. As this almost-circular piece rotates between its neighbours, the potentiometer shaft will rotate with it and inform the Arduino about the elevation of the laser pointer.
The base of the potentiometer is anchored to The Redpointer's base by a section of tongue depressor glued to another piece of wood.
Notice the little semicircular notch cut into the flat top of the middle piece of wood. There is a hole drilled down at the base of that notch just wide enough for a potentiometer's shaft to fit inside. The second potentiometer is eventually glued into that hole, but first it is attached to another tongue depressor. Two CDs act as a bearing between the wooden block and the tongue depressor. Once the potentiometer is glued in place, it acts as a sensor for the laser pointer's lateral rotation.
With the two-axis base assembled, a simple gun-like handle (made from three pieces of glued wood) is attached to the top. This will allow for simple one- or two-handed control of the sensor turret.
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