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Garage Fix (At Last!)

Beam Emitter

Since we move into our house nearly 18 months ago we’ve been dealing with the super-annoying “sometimes it works” garage door opener. Or perhaps “garage door closer” is more accurate. In the olden days garage doors just closed, and if you got crushed it was your own damn fault. Somewhere along the way (in the name of “safety”) manufacturers added “External Entrapment Protection Systems”, which are typically an infrared emitter and an electric eye that sees the beam from the emitter. When the beam is interrupted (like when a stupid child runs under the closing garage door) the door reverses and does not close. No child crushed, no harsh lessons in being careless learned.

Look, I’m not in favor of crushing children, but with the sun shining directly at our garage opening, 75% of the morning we’d leave the house we couldn’t use the remote to close the garage door. I didn’t want to completely disable the sensors, as it would probably get us sued if a child did get crushed. Also, I’m all for safety. (Really. I am. Tell the insurance company that.)

My first attempt at a fix was adding a gaff tape flag to the electric eye. This did almost nothing. I did find that blocking the sun with my car and/or body sometimes worked. So imagine that when I pulled the car out of the garage I had to get out and stand in front of the door (very close to it, in fact, almost close enough to be hit by the door) and try to block the sun. Sometimes it worked, and often it did not. When it didn’t work we’d have to go into the garage, use the manual release to shut the door, lock it, and then reverse the whole procedure when returning home. #PITA

Eventually I added a button (duh!) to attempt to manually override the sensor. Sometimes it worked, other times it did not. Occasionally it would get 90% closed, then open again. Argh! Reflecting light? I don’t know…

Electric Eye

Supposedly you can added some tubes, but I never got around to that. The garage not closing when you leave is just annoying enough to aggravate you, but not annoying enough to spend real time trying to fix it.

The new solution (which is working well so far) involves extending the electric eye a bit further in from the door, and angling it to point at the emitter. Some scrap wood and zip ties pulls it all together quite nicely.

New Garage Beam Layout

Here’s our new set-up. Granted, there is a bit more room where something could get crushed, but it probably won’t be me, because now I don’t need to stand centimeters from the door as it’s closing.

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Teensy: First Time

In case you’re wondering, this is what you see the first time a computer running Mac OX sees a Teensy (or other controller) acting as a USB HID device. (You know, like a keyboard.)

Mac OS X Keyboard

No worries, just hit the “Continue” button…

Mac OS X Keyboard

And then hit the little red dot in the upper left to close the window. Hopefully you’ll only see this the first time.

That’s it!

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Mixing Imperial and Metric

Converting Imperial to Metric

In an ideal world, we’d all be using the Metric system, but the world is far from ideal, and math is confusing, so we’re sort of stuck.

Most of the design work I do for objects (laser cut or 3D printed things) is done in millimeters. This makes sense, and is oh so easy compared to trying to use those damn inches! Sadly, I grew up with Imperial Units, and while I can roughly estimate what 12 inches is, I still have problems visualizing something like 100 millimeters. I can usually remember that it’s about 4 inches, but it’s still difficult to put my hands in space 100 millimeters apart without first converting it in my mind to 4 inches.. Dammit!

Converting Imperial to Metric

So I end up converting values. Typically using Google’s conversion utility (because I’m in front of a computer 98% of the time I’m designing something.)

So if I wanted to find the Metric equivalent of 69/500″ (also known as 0.1380″) which is the diameter of a 6-32 bolt, I can find out. Oddly enough, when it comes to the small numbers, visualizing things is the opposite! It’s easy to visualize 3.5mm but impossible for me to imagine what 69/500″ looks like. Whatever!

Here’s a simple chart of bolt sizes I’m posting just for my own use.

5-40 0.1250″ 1/8″ 3.175mm
6-32 0.1380″ 69/500″ 3.5052mm
8-32 0.1640 41/250″ 4.1656mm

Update: A larger chart!

While I would love to use Metric hardware more often, it’s expensive! I usually just buy random bits from the local hardware stores, and the Metric stuff is in short supply, and cost more. I find it quite annoying. I don’t know if prices online are any better, a quick search seemed to suggest not.

(And don’t even get me started on pixels!)

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Robot Builder

Robot Builder

Hey, it’s a new book! Robot Builder: The Beginner’s Guide to Building Robots is now available!

Last year after I served as Technical Editor for John Baichtal’s Arduino for Beginners I was fortunate enough to be asked to again fulfill the role for Robot Builder. (Obviously I said “Yes!”)

Books take a long time, and there’s a lot of reading involved, and for my part, a lot of research and checking on technical data. It’s definitely enjoyable though, and there’s a lot to learn along the way.

(I’m not currently working on any books, but if you’re in need of Technical Editor that’s near one of my areas of expertise, I may be available.)

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Drawbot Tool Holder

One of the issues I’ve had with the Friday Night Drawbot is the part that holds the tool has never been very solid. In early revisions I used corrugated plastic, and would just use an X-ACTO knife to cut a hole for a Sharpie, and it would work well enough, and when the plastic wore out, I’d replace it with a new piece. (The most recent body design failed miserably at producing a good pen holder.)

Since I’ve been using other things besides Sharpies, including pencils, charcoal, paintbrushes, clay tools, etc. I decided to design a proper tool holder.

Tool Holder Mockup

I typically use Inkscape to design laser-cut things, but often visualizing a 3D object, even if it will be made from flat pieces, can be difficult, so I decided to use OpenSCAD to model it in 3D. It definitely helped me picture how it would be assembled. I also had the idea of exporting the “plates” from OpenSCAD into DXF files I could then use for the final laser-cut design but that failed miserably.

Sizing

Here’s the start of my layout in Inkscape with the pieces laid flat. This let me get a good idea of the dimensions.

Tool Sizes

I wanted the tool holder to be adjustable, and handle tools from 8mm wide to 16mm wide. (In this top view, the blue circle represent the different sized tools, the yellow piece pushes the tool into a v-shaped piece to hold it tight.)

Layout

Here’s a top view of the layout with some guides to help align things. This is designed for 3mm Baltic Birch (though acrylic could be used.) The slots and tabs are all set for 3mm. There are no fasteners planned as I’ll be gluing it all together.

Layout

Another view from the top, this time with some pieces rotated 90 degrees to see how they will fit together.

Laser Ready

All of the pieces laid out flat and ready to be laser cut. I used 3mm Baltic Birch which worked well using the Epilog Zing 40 watt laser cutter at the DCRL. (I also ended up adding yet another laser cutting workflow to my list. I now have three different methods depending on which of the four lasers cutters I typically use.)

Tool Holder

Assembled with some wood glue, and using rubber bands to hold the tool in place. It works… sort of. I’m already planning improvements, so expect version 2 to arrive by next week. I may switch to a screw mechanism for tightening, which was my original idea, as the rubber bands aren’t working as well as I hoped.