2015-10-30 (F) Weekly Summary

I was all set to take pictures of this project and be finished. The more I looked at it the less I saw that was actually complete. Despite wanting to be done with this project it wasn’t finished. Sure, most everything worked but it didn’t feel complete. Instead of taking a few pictures and adding labels I wrote up a list of all the things which needed to be done before the project could be called complete. This project has gone on a long time and I want to be done but here the difference between having a half-baked product and something that I’m proud of. At the same time this is a gamble, I’m 95% done with this but there’s still time to give up.

First shot. Not going to be used for the final instructions

The first problem to tackle was to make another proximity sensor. The old one had short wires which made it impossible to aim correctly. Liquid tape had been used to protect the back of the original proximity detector but the parts were so inexpensive that it made more sense to keep it for future use and build a new one with a long cord. Ethernet wire salvaged from a cable which was easier to bend. Wires were soldered to the back of the protoboard like before but the wires going to the screw terminals were arranged more neatly than before to save room in the enclosure.

New emitter-receiver tube

Neat wire layout

Before liquid tape was applied the program was tested. Connections all seemed good but it took two days of debugging to get the sensor to work. The proximity sensor couldn’t tell the difference between an obstruction and empty air. Feedback told me that there was always an obstruction. Resistance was added and a variable resistor was even tested but nothing gave reliable feedback. The problem turned out to be light leakage at the BACK of the tubes. Light from the emitter was sneaking out behind it and affecting the receiver a couple millimeters away. It only took a scrap of paper to block the offending light beams and confirm the light leakage problem.

Proving the light leakage problem with a scrap of paper

Cleaning up the hardware on the wrist mounted rig was more than just a little polish. It involved taking out all the nuts and bolts then swapping spacers, replacing ordinary nuts with nylon insert lock nuts, trimming long bolts and finally reassembling everything in the correct order. Fortunately the reassembly went quickly since the parts all fit neatly and were finally sized appropriately. One problem with reassembly was putting the controller back into the enclosure. The power would fail when it was pushed into the bottom. Naturally this seemed like a shorted connection but it could not be replicated outside the enclosure. The problem was the exposed reset button the Arduino was being pressed against the bottom of the enclosure. This switch was removed.

Cleaned up wrist mounted rig

Shortened bolts and properly mounted servo horn

Reset switch removed

Necessary changes to the program were written down but haven’t been done. For example, the weight of the keyboard causes the servos to move out of position while resting. This can be remedied by continuously supplying the servos with the correct position.

Servos slipping while resting with keyboard in position

A large white foam board was set up to take pictures. White was used because it will be easiest to remove. My cell phone camera was tricked into overexposing the photos so the background was a brilliant white while the subject was in focus and a reasonable tone. A worksite light and a fluorescent light were used to blast the white foam board and subject with light.

Photo area

Isolated picture of keyboard

Labels were added to the isolated photos. Those labels were taken from a comprehensive list of the parts used in this project. The part list included names for each part printed or purchased.

Labeled keyboard picture

Labeled wrist mounted rig

The rest of the weekly summaries have been arranged by date.

First time here?

Completed projects from year 1.

Completed projects from year 2.

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