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This page holds a few projects that take over "manual" tasks.... button pressing and knob spinning.
GPS button presser
GPS button presser
This project was made to solve a very specific problem. I use a Garmin Nuvi GPS for geocaching, and registered as a premium user to get the feature of uploading cache locations in bulk from my computer to the GPS. Unfortunately, I loaded way too many... 504 caches, plus assorted parking locations and waypoints. It was too much; I ran out of space on the GPS for putting in other Favorites. Then, to my horror, I found that the GPS design allowed me to load on new Favorites from my computer, but not remove them! And there is no way to remove Favorites in bulk.... without this machine.
GPS button pressing machine.ldr
To remove a Favorite manually, I first get to the list of Favorites on the GPS. From there there are 4 button clicks required - on the favorite in the list, then the same favorite in the map, then Delete, and then confirm with a Yes.
My goal was to manage the entire deletion with a single crank - one motor, no sensors.
This machine has 3 trip-hammer style fingers, placed to make the 4 button clicks (two can be in the same location). That is, the finger is pulled down to the screen by a large rubber band, but a cam mechanism pulls it away from the screen most of the time. The trip-hammer design is important to get enough pressure to register on the screen without worrying that I would crack the screen. I also wrapped a thin rubber band on each leg to concentrate the button press more precisely .
The cams are built by inserting technic pins into the holes of 40 tooth gears, with the rounded end of a technic beam (the back side of the finger) sliding along the pins. Removing a pin lets the arm pivot further to contact the screen. This cam design had an unexpected benefit. The arm gets to move in a bit between pins, and since the arm is attached to a rubber band, this means that as the gear is turned it snaps into 8 positions - as though it were a digital design. This made timing the different presses much simpler.
Originally I ran the machine manually, and then I tacked on a motor, with some gearing to make sure it went slowly enough to be registered by the GPS. Once it was fully operational, I let it run for an hour and came back with all Favorites deleted!
Etch-a-sketch machine
Etch-a-sketch machine
Haven't you always wanted to program your etch-a-sketch? I have. The only thing remotely tricky about this build was getting a good grip on the knobs of the etch-a-sketch (which don't just happen to be on LEGO stud boundaries).
I built this using the RCX, with a goal of writing my name in cursive. To get nice soft curves, I did a lot of manual PWM, moving each motor for just a few ms at a time to get them in different ratios. Unfortunately the RCX programming environment doesn't have real functions. I ran up against the memory limits in the RCX native environment.... had to do some compression to get there.
So I added a third motor. One of the knobs is driven by a gear train with a differential, to add or subtract the scaled speeds of the two motors. This gives it 9 different speeds, assuming each motor is off or on in one direction or the other, as long as the motor speeds are scaled differently. A 3:1 ratio makes the options equally spaced.
Effectively, this is a hardware accelerator. With the third motor I can get lots of angles with motors completely on, which requires much less code.
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