Tag Archives: cnc

Automated airframe

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It appears the road to a GPS-Controlled airplane (Drone) is paved with broken Styrofoam. Pictured above is on of my first automated flights on an old P-47 I had. It lived up to its historical nickname of “Jug” which is how they look when they nosedive in to the ground. To move forward I am going to try to make my own airframes from a $15 AirHog glider I picked up at Target. I have a few of them on hand, and they are pretty big. Each wing is 2′ long. To start I needed to cut off the top, so I can CNC in some pockets inside to hold an arrow shaft (for strength) and to house all the electronics.

I do not have a Styrofoam cutter, but I do have some nichrome wire I used as a electronic firework igniter so I hacked something together. I took the blade out of a tree saw I have, strung some nichrome, added a 12v wall wart and sliced away.

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I have started laying out the electronics, servo mounting holes, and cuts for flaps in my cad software, and will share those results when I get them on the CNC.

Bat Holder

My son plays baseball, and keeping equipment organized is an ongoing challenge. While sticking bats in the chain link fence is a time-honored tradition, I thought I would whip up a bat holder. I can’t take credit for the concept, as one of the municipal parks had a similar solution permanently mounted. Mine is a knock-off using 2″ pvc pipe and some rope.

The machining was very simple, its basically two rectangles per bat. The only trick was to do one series of rectangles, then rotate the pipe 90 degrees before doing the second.

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bat_holder_done

Sheldon Cooper LineArt

My wife started a new project at work, and as this project is a big one, it meant a new notebook! She got a very nice green moleskin, but the cover was quite plain. As we both love the Big Bang Theory I was tasked to put a likeness of Dr. Sheldon Cooper on the cover. Rigged up a sharipe in a pen holder, and off to the races!

Original picture, and gcode here.

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Tie Fighter in ASCII

I saw this CNC halftones article quite some time ago and setup the the CAM drawing quite some time ago. I never really got around to routing it, as I wanted to test it in two-color plastic instead of the painted plywood the original authors used. As luck would have it, BF plastics had some white/black material on clearance last week so I picked up half a sheet. The material is only 0.1″ thick, so I used 3m spray adhesive to mount it to 1/2″ plywood. About 30 minutes or so with a 60 degree v-carve bit and it was done! I need to pick up a 45 degree bit i think, as this one did go a little deep in places, you can actually see some wood on some of the wider letters. Still looks sharp!

The .dxf and gcode can be found here.

tie-fighter-crop

On the machine:

tie-fighter-in-flight

Word Clock Build

This project was one of those long-running ones which took almost 7 months from when I saw the first one out there and wanted to make one, to when I actually got started.  One of the big catalysts was Joe’s blog post on his build – so hats off to him!  Joe did perf board wiring, and I wanted to create a circuit board for the task.  The reason for this was twofold: (1) I hate perf board and (2) I wanted to build the atmega circuit and bootstrap it myself.

So if you watch the video below, you will see I failed at getting my atmega to run.  Could not figure it out!  Next time I will surely include additional LED’s (pin 13 anyone?) to aid troubleshooting.  So, that said in the zip file attached you will find my eagle schematics.  If you use them, be aware the microcontroller portion requires some additional scrutiny.  Maybe its fine, and I just messed up the wiring.  Who knows.  If you want to take a peek at it and give me feedback I would appreciate it!

Other big change/addition from Joe’s build was I added a Real Time Clock (RTC).  In my case I used the ChronoDot.  It is much more accurate, and tracking time in code was MUCH easier.  Here is my code, eagle schematic, and .DXF file for the led array.

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2013 Christmas light controller :: Part 2

The controller portion of this project will be based off an Arduino Mega 2650.  Of that the intent is to use 30 of the available digital channels.  The target for 30 is arrived that for each remote board I can get 6 channels pretty easily.  That is driven by 8 wires in an rj-45, with 2 being used for power – leaving 6.  Based off how many lights we actually wanted to hang, we decided 5 groups of 6 channels should fit the bill.  Getting to the design on the Arduino shield I quickly discovered I was limited by the 4×3 inch area provided by the freeware version of Eagle PCB design.  In hindsight I should have just ponied up the credit card and purchased the hobbyist version.  I will probably end up getting that for next years’ inevitable growth.

With the working limitations I had, I needed to break the shield up into two pieces, as I could not fit everything in the 4×3 working area.  I ended up making one board for 18 channels, and another for 12.  Here is a zip with the eagle files.  I warn you in advance the .sch files are not pretty… 🙂  They are free to use for non-commercial purposes.

Overall its a pretty simple design.  Arduino pin goes high, opens the gate on an NPN transistor.  This grounds the led on board lighting it, as well as proving a ground leg for the remote board which turns on the remote LED and Optocoupler which in turn flips the triac on.  Simple daisy chain effect.

master board

Turning that into a working board was a bit trickier, as I couldn’t get it designed as a single sided board.  That mean I had to get the board aligned perfectly after milling one side and flipping it over.  After the first board which I got close but not quite (pictures below) I figured it out on the second board.  It turned out to be much easier than I was making it..

Of importance is the get the board aligned straight along the x axis.  I did this by routing a .1″ deep square the board fit in.  The square was oversized, I just wanted a straight x-axis line.  I then mounted the board against that axis with double-sided tape.  make sure there is 100% coverage on the board.. don’t leave tape gaps as board will flex down on z axis in those spots.  I then aligned the x/y corner and etched the bottom of the board, and drilled the bottom.  The gcode for these operations were created through pcbgcode which I wrote about in another article.

To get the top of the board, flip, re-tape, and align to the x axis.  Then jog the CNC to line up on a few selected holes from the previous drilling operation.  In eagle, hover your  mouse over these holes and you will see the x,y location.  Enter these in your machine, and validate a few other holes.  You should be good to go for etching on the top!

eagle xy

First attempt with trying to measure offsets for the front/back operations.  This created some offset holes, which had to be managed a bit with a dremel grinder.  Still a usable board.

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Second attempt using the eagle offsets described above, which came out very nice.

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Next update will show assembled boards, and hopefully a video of everything operational.

2013 Christmas light controller :: Part 1

I really don’t like hanging or taking down Christmas lights.  I generally do the bare minimum my wife requires to get through the holidays.  I HAVE always been intrigued with the computer controlled lighting displays that are synced to music.  Last year I got into a fun partnership with one of my neighbors.  He wanted to do the whole music shebang, but didn’t know how to do the hardware side of the equation.  Mmmm.. symbiotic relationship.

Last years’ system was a 12 channel deal controlled by a basic arduino.  Worked well enough, built on perfboard and stuffed into a 2-gang junction box.  Downsides were it was not engineered well at all, with the 5v logic intermixed with the 110v ac.  It also required a lot of extension cords as all 12 channels/outlets were combined at the same location (in his garage).

So, we are at it again this year.  The objectives are:

  • increase to 30 channels (arduino mega)
  • hub/spoke design.. with centralized control and 6-channel remote boards to minimize extension cord usage
  • add LEDs to show when channels are on/off for easier programming/debugging
  • safer design.. with better isolation between logic and 110v.  also include little things like fusing on board.
  • waterproof enclosures as we are approaching this as a modular multi-year initiative

So with that in mind, I first created one of the satellite boards.  I designed this in eagle, with a goal of keeping it a single-sided board for easy machining.  The initial trial board machined out well (see previous posts showing generation of gcode from eagle-cad).

First run was pretty good, and soldered up into a usable board.  I did have to hand-dremel a joined trace.  Improvements identified were:

  • Increase the amount of cnc routing around the traces to improve isolation
  • fix the 110v connector pin sizing.  I had them at .1 and they are really .2, so my screw terminal connector wont fit
  • Add a fuse which I forgot to add
  • Increase trace size where possible.  Mid-trace holes sometimes cut the whole trace, so had to bridge with solder.

Did solder up ok into a usable board though:

After a few eagle cad changes and some modifications to the cnc gcode generator you can see the a/b comparison of the boards.  With the original run on the right, and the new one of the left.  Machine time takes about 30 minutes/board.  Using a 60 degree v-carve bit… probably not the best tool for the job.  If you have recommendations on bits please let me know.

CNC sign from Plywood

My neighbor is starting to brew his own beer, which is a great boon to me.  In an attempt to curry additional favor I offered to make him a sign for his garage.  My intent was to do a trial run in plywood, then do a final in maple with walnut letters.  While doing a clearing operation the main portion of the sign, I got into a layer of plywood that had a very nice grain/color.  I am no real wood expert, so I don’t know what it is, but it was very pleasing overall.

Got off easy on this project, just routed the letters down into the next layer of lighter colored wood, and I was set.  Few coats of rubbed poly and off to the neighbors.

Lesson learned – look at the edges of plywood when routing, you may be able to use the various layers to your benefit!

HT Controller : Troubleshooting

So I had some issues when putting the final product into use.  Which is to be expected, but this bugger had me opening the case at least 6 seperate times..

Issue 1 : when the 5v relays would kick in, it my 7805 voltage regulators didn’t have the reserver to engage them both at the same time.  I needed to add a capacitor.  I did it the easy way, and just screwed it into the terminals.  The +5v is wired in parallel so both relays benefit.

Issue 2 : I used digital pins 0 and 1 on the arduino to control the relays.  Turns out those pins are used for serial communications.  So when updating the board the relays woudl clickclickclickclick like no tomorrow.  No good, had to use different pins.  Obviously I didn’t account for that on the board creation, so they got solder to the pins directly.  Picture is a little out of focus, but it is the orange/yellow leads in the foreground.

Issue 3 : In the external power strip where 6 seperate relays live and are controlled by the arduino here, I made a mistake in that I didn’t have any 10k pull-down resistors on the 6 control lines.  I should have put them in my original circuit, and instead I added them via a little ‘daughter’ board I added to my original circuit board.  Oh, and if you actually jump to read about the external power strip know I took the power supply and arduino out as they are replaced by this build.  All that is left is the transistors and relays.

Ribbon cable removed, and ‘riser’ pins installed:

Daughter board freshly machined:

And installed:

Lessions Learned :

* Patience.  I had to keep telling myself that there was no way I would get everything right on the first try.

* That a 7805 regulator needs a headsink in most cases.

* That a 7805 also needs filter capacitors.  You can’t just plop it in a circuit and expect clean output.

New sign for the workshop

Took a shot at making up a sign for the workplace.  Learned quite a bit in the process, and wanted to document a few of those learnings for the proverbial ‘next guy’.

I used 3/4″ mdf.. and a 1/4″ upcut spiral bit to do most of the cutting.  The circle logo and ‘aperture’ letters are .4″ above the surface, and the ‘laboratories’ letters are .2″.  I profiled the letters after the overall pocket was created with a 1/8″ bit to get more definition.  This all worked ok except for a few things:

  • An ‘R’ and an ‘I’ in laboratories popped off.  The MDF doesn’t hold well when the letters get small.
  • I re-routed those letters and then glued them on.  In that process I realized that NEXT time i would just route all the letters out of another (thinner sheet) and glue them on.  It would save many hours of pocketing work.
  • Glueing the letters would also allow for easier painting as you could paint everything seperate and then glue them on.
  • On the topic of paint, for $3 for a 1/2 quart home depot will create color matched ‘sample’ paints… awesome for this kind of work.
  • Be careful when shopvaccing around the machine while its working.  At the end I looks like a skipped a few stepper moter steps on the x axis, so i have some rough edges on the right side of my letters.  I vaguely recall the router pinching the hose against a letter while vaccuming.. that may have caused it.  If it didn’t.. well thats a problem for another day.

So I learned a lot, and have a fun sign for the garage – its about 36″ long for reference.