Author Archives: widgetNinja

Calling this an amplifier build would be deceitful

Its more of a box build.

So browsing adafruit.com a while back I came across a class-d amplifier board they recently introduced. What is interesting about class-d amps is they are very efficient, thus generally needing no heatsinks. Seeing boards like this I am frequently reminded how far things have progressed since my electronics classes in 92/93. In that class I tried to build an amplifier for my car, and really didn’t get much further than etching the board. The traces didn’t etch cleanly, even using the advanced (at the time) sharpie+acid method. After getting board patched up with jumper wires to fix screwed up traces I then realized how expensive power mosfets were for a high school student. End of that project.

So I of course bought this little amplifier board immediately. There has been some conversations around the house that we should have music upstairs. So this board + an old ebay purchased airport express should do the trick nicely. So board in hand, it needed a box. I always skimp on the box, but in this case the board was pre-manufactured so I could afford to put some energy into its home. I haven’t done anything with any hardwoods on the CNC yet, and I had some walnut I got from a friend when he moved. So I set about making a box.

I have no jointer, so surfacing with the CNC, using a 1″ bit.

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Flipped the board over and routed a box + lid.

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The lid didn’t fit perfectly, and required some chisel work on the inside lip to seat properly. The outside also needed some time on the disc sander to be flush all the way around. I really need to upgrade my y/z axis with some linear bearings. Maybe this winter.

With the overall box built i used the drill press to put some holes in the back to mount the 1/8″ input, the 12v barrel jack, and the 4 speaker posts. Of course one of those holes is a square, so I had to spend some time with the files.

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Before mounting anything I needed to finish the back, as it would have been hard to do with all the posts etc in place. I was just going to do a basic coat of poly as this wood was very nice. Got out the rattle-can and gave it the first light coat – which did not work out well. I was not paying attention and grabbed black spray paint instead of my clear lacquer. How could that happen?

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Quick wipe down with mineral spirits, but black was deep in the pores. Decided to just blast the whole thing with black, wipe with spirits, and sand again. Turned out ok, gave the wood a darker appearance – although this wont be my ‘go to’ finishing technique.

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Mounted the amplifier inside with double-sided foam tape, and soldered up all the connections. Pretty basic.

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Functionality test with a 12v 1.5A switching power supply I had in the junk box, and it wouldn’t power up. I kinda forgot that 20w per channel is 40w. At 12v you need 3.5A at full power. I tested instead with a 11.1v Lipo battery from one of my RC airplanes, using alligator wires to the board and all was fine. (fatal mistake)

Double checked everything, glued the lid on, and finalized the finish.

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I sourced an old pc power supply, as they can handle crazy current, and modified it to work w/o a pc. Grounding green wire is all it takes. I pulled out all the un-needed connections and put a barrel connector on it.

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Brought everything inside, connected up the speakers, power, airport express… and it doesn’t work. Much testing ensues, still does not work. Shamefully bring it out to the garage, and bust it open with a chisel.

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Of all things it turns out the barrel connector plug was bad. That was why the initial power supply didn’t work. That is why new power supply didn’t work. The test battery worked because I alligator jumped the leads to the back-side of the connector. Dang.

So now the power supply is hard wired in and everything works fine. This amp does a great job driving bookshelf speakers, and i would use it again. Things I would do differently if i were to do this again (hint : i won’t).

    Not use black spray paint by accident
    Put an indicator LED in the box so I know if there is power
    Turn the box ‘upside down’ and inset a plexiglass bottom that is screwed in (for access)

Overall a fun project, and I learned how nice walnut is to work with. I also finished an amplifier project, that i started over 20 years ago!

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.

Pinball Machine Build

Been pretty lax about updating this blog recently. I have undertaken a fairly time consuming build of a virtual pinball machine. I have been making posts in a forum on that topic as I have required input from that community throughout the build. I am almost(ish) done and will make a video highlighting the process when complete. In the interim, if you want to see some of the gory details you can check out my build log.

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Pinball Build

Update : Build complete!

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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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.

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On the machine:

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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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Lighting Controller :: Part 3

I got the components mounted on the main and remote boards. After much deliberation we dropped $12 per remote node to pick up some waterproof plastic ammo boxes to put the electronics in. These boxes will be out in the yard exposed to snow/rain. The boxes worked out very well, as the 3-gang outlet box fit nicely inside. Just drilled a hole in the bottom so the cords can go in/out.

Wiring up the outlets was pretty easy. Common wire was shared across them all, and the hot (black) wire was sourced from the circuit board (triac). I did not use any ground wire as the Christmas light strings don’t have ground. I also used a pretty light gauge wire as I will only be driving a single string of LED lights per outlet.

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Got everything wired up at the neighbors and everything worked well. Even with 100′ cat5 runs to some of the remote boxes everything worked well. We did have some flakeyness where it would lock up occasionally after a few hours. I upgraded the wallwart power supply to an old computer supply, and at the same time fixed a solder joint for the ground wire that looked ‘cold’. Not sure which of the two upgrades fixed the issue, but all is good now.

Below is a picture of the main controller board wired up on the workbench. Will post a video of the light show in the next update!

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One thing you may notice is the FTDI controller connected via USB. This is due to the fact the Arduino Mega changed the way they emulate usb/serial. This new chip on the arduino is not identified by the software running the lighting show (Vixen). Using an older-style FTDI board remedied that situation…

Believe christmas sign

Its rare that my wife asks me to make something for her. I think its hard for her to get over some internal negative connotation she has with ‘homemade’. This year for Christmas she did ask me to make her a sign for the front yard. My marching orders were for it to be as big as possible, and to say ‘Believe’. My CNC machine has only a 2×4′ bed, and for the first run at this I didn’t want to be patching together multiple boards. I chose to use 1/2″ plywood, as painted I think it will hold up pretty well to the elements.

First order of business was to grab an appropriate font. I usually go to 1001freefonts.com. No affiliation, but they have a nice selection of free fonts, and there is no hoops to jump through to get them. I chose the new font, typed up the word, and expanded it to fill my 2’x4′ work area. I then did a profile around the word, leaving a 2″ gap all around. The ‘fanciest’ part of this design was to use vectors to draw inside the letters to outline where the lights would go. My software could then space holes along those lines, and I chose to space them 1″ apart – end the end this worked out very nicely. The only other open question was how big the holes should be. Using my calipers I found out the lights were of inconsistent size. Most were around 0.21″. In the top center of the drawing you can see where I had a few holes of differing sizes that I machined initially to determine which size hole would have the best ‘friction fit’ to hold the lights in.

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I painted the 2×4 sheet bright red and let it dry overnight. From there it was off to the CNC. I had big plans to use a contact paper (for lining drawers) mask for masking off the letters so they could be easily spray-painted white. This did not work well, and I would not do it again in the future. The mask isn’t super sticky, and it had a tendancy to pull up when routing. It also had a tendancy to ‘melt’ when sprayed with the spray paint I had. Regardless, my first machine operation was a profile to cut the mask with a downcut bit. This will also prevent tearout on future machine operations using an upcut bit.

So what you see here is the mask, along with repairs to mask made with blue painters tape.
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Second operation was to pocket the letters. This was just a shallow 0.2″ pocket. I then cut out the sign, spray painted the pockets (letters) and removed the mask. The led lights inserted from the rear with a friction fit, no adhesives used. Sorry I didn’t think to take more pictures of that process. Below see both day and nighttime photos of the final product.

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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.

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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!

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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.