The Glowhawk: OFBC Gaiden

Update: Plume added, rebuilt using thread and pipe cleaners to keep it upright and separate strands, removed plasticard sticks and zip ties.  Also pulled the EL Wire which is being repurposed in my son's EL Hoodie.

We were only able to print a few OFBC 2.0 cases before DEFCON 26. The leftover parts would have sat in my toolbox for quite a while if not for a serendipitous mistake: I ordered the wrong color LEDs from Sparkfun. This plus a little construction advice from a seamstress helped me cobble together the glowing headgear that is The Glowhawk

My courage and thinning hair prevents me from getting a mohawk while at DEFCON, but I've always wanted one. Instead I started to create one with a networking theme. Pipe cleaners in the color of Cat6 twisted pair served as a thick mane anyone could be proud of. This was wired onto a hat as a test. It looked OK, but it was kind of stubby to wear all on its own.

The LED driver for the OFBC is overdone. A single charge can last 10 hours on the original model. I wondered how much it could handle in terms of output, and a little breadboarding showed me I could wire several of the LED modules together as long as they were in parallel. Now how to use them?

The LEDs are these 3W green modules with attached heat sink. Direct eye contact is not recommended (hence the pains we took to use momentary buttons on the OFBC). On the beer light, we diffused the over-bright light so it could be sculpted by the drink it passed through. I was inspired by a fiber optic dress I saw elsewhere and found fiber optic table centrepieces for dirt cheap on Amazon. Some hot glue joined the disassembled fiber optics to the bright LED. The mane of glowing green was born!

With this fresh take in hand, DEFCON was upon us. I packed my things and thought I might take a crack in the evening. The Richard Cheese show was the perfect venue to solder everything together. The_bozo and I found a better place to work where the hot glue gun could run safely. I transferred the existing Cat6 mohawk to a bright green John Cena hat from Goodwill. Inside the channel that ran between upturned pipe cleaners, I hot glued the modules and fiber optics. Zip ties kept the fiber bundles from flopping around too much.

I consider the Glowhawk a great success, if a tad impractical. It lasted about 2 hours on a charge, and I was able to walk around wearing it with the mobile party crew for that long before it got uncomfortable.  A photo of me wearing it hit the DEFCON Closing Ceremonies, and my son keeps trying to steal my remaining fiber optics for a lamp in his room.

Future improvements include better internal support, googly eyes to cover the logos, and a fifth plume to fill out the front. See you next year!

OFBC 2.0

For Toxic BBQ 13 (DEFCON 25), we returned to the OFBC to see if we could improve the design and add some needed table decorations.

The first step was to simplify the PCB creation. I created a new layout in Fritzing that reduced whitespace. It also moved off-board components like batteries and the LED modules to use JST connectors for easy installation and swapping.  OSH Park did a great job with the PCBs. I was able to directly convert the Fritzing designs to printable format. Each board was less than 2 bucks by the time we finished. Never again will I make my own PCBs by hand. 

Sparkfun supplied most of the same components for about 15 bucks per light. Here is an updated BoM for this case:

• Battery: 850mAh Lipo
• Switches: Hinge Lever Micro Limit Switch
• Mosfet: N-Channel 60V 30A
• Transistor: NPN Transistor
• Resistors: 100K and 3.5 Ohm Resistors
• Slide Switches (ensure pitch matches the PCB)
• LED: Cool White, Aluminum Backing

Next, we redesigned the case. Instead of a three piece design requiring glue to assemble, the two pieces would be a base and a lid with a logo. Everything could be screwed into designed posts and covered with the lid. It was a snap. Production was easier with Shapeways. However, this lead to had longer lead times that prevented us from delivering to the barbecue. The prototyping went well and matched the designs, but the mass printings were so delayed that they didn't arrive in time for the barbecue even with expedited shipping. The resin product looked much better than the filament-printed 1.0 model. The cost at 20 bucks or so each was not prohibitive, but it certainly wasn't mass-market ready.

PCB at OSH Park
Case Files on GitHub

Design Pics

Updated Lid Design for Toxic BBQ 2018

Dan Learns How To Blog...

Here's a quick retrospective after 25,000 page views.  In 4 years, topics were all over the map.  Mainstream topics like hacking Skylanders brought organic traffic from search engines.  Posts in a niche subreddit has a way of bringing in links years on.  The Cards Against Mormonism and boardgame tables still get a few hits per week.

Advertising revenue was an interesting experience.  A free site has generated a whopping $10 in 4 years from Google, and I haven't seen a cent from Amazon referrals.  In all, it's interesting to see how hard it would be to make a living with just ad revenue.  Sponsorship makes a lot more sense in this light, but impartiality takes a hit.  The web runs on a sea of quid pro quo.

In terms of authoring content, I learned a few things that English class couldn't anticipate in 1999. Mentioning specific dates instead of relative dates keeps readers from having to calculate in their head and increases the possibility that they will stay for the whole article.  If you have a story idea that has been sitting in your drafts for more than 3 months, delete it.  Your enthusiasm to talk about it is probably not going to grow after that long.  Build logs and multi-part posts should be split into shorter posts.  This will ensure you stay on topic and don't ramble.  And don't talk about how long it's been since you last blogged.  I can assure you that no one it waiting with bated breath for your review of Behat's 3.4 release.

On to the next 25,000!  Hopefully it won't take me 4 years.

Failing Faster, Succeeding...Soon?

I listened to a good podcast about having and executing on ideas.  Here was the gist of it:

1. Have an Idea: Gather info directly from customers.  Implement now or Punt for later
2. Once implemented, get a Minimum Viable Product to a Website, county fair, etc.  Fulfillment can be slow at first.  Persevere and refine or Punt
3. Once it is selling, enter a Customer Validation Loop and handle their concerns first.  New ideas?  Start at top.  
4. Once major customer concerns are addressed, enter a Product Design Loop: Change design or manufacturing as needed.

The core of the idea is to fail faster in the hopes that you succeed sooner.  Your backlog of unvalidated ideas are there to experiment on and validate.  Then you Implement, Persevere, Resolve and Redesign or Punt and wait until you've churned through your good ideas.

http://www.ssireview.org/blog/entry/fail_faster_succeed_sooner/

Another formulation of this is the 2-2-2-2-2 method.  When you are trying to determine if an idea is feasible, first spend 2 minutes getting it down on paper.  If it still captures your interest, spend 2 hours fleshing it out.  As it grows, time box your commitment to the project.  See it through or bin it.  By the time you're spending 2 weeks or months on an idea, it should be clear whether it can bear fruit or not.  I cannot find an online version of this idea.  If you can place it, let me know in the comments.

While this applies to product development, it can also apply to hobbies, chores and other activities.  Have an idea for homemade Christmas presents?  Try it out on a small batch before you become consumed with a monster of a project with no practical timeline for delivery. Have a request from a friend to help you with a project?  Spend a few minutes talking logistics.  If you get down to a trip to the hardware store, make sure you can finish that phase with results in an afternoon.  Re-evaluate before committing to future efforts: is the benefit still worth your collective time?

Magnetic Bottle Openers

In the tradition of doing something snazzy for the DEF CON Toxic BBQ, I created a bottle opener that would both mount magnetically as well as catch bottle caps with the same force. 

Amazon had a selection of sturdy bottle openers by Starr X, and a particularly helpful blog post by K & J Magnetics helped me pick out the featured magnet.  I'm relying on the interesting grain of the Indian Rosewood to give the piece character as I didn't have the tools to do a fancy profile, and my router bits are incredibly lacking, so I just went with dog-eared corners and a chamfered edge.  The burning visible on the below pre-finishing shot (accompanied by my favorite Wasatch brew) was due to the bit I used.

The magnet was epoxied in place after I cleared out a spot for it.  In order to prevent the opener from sliding on slick surfaces, I added slightly inset tiny rubber feet.  This also set the opener off from the fridge by just enough that you can get your fingers behind it to pry it off with ease. Lots of sanding from 100 to 600 grit made a great smooth base for some stain and spar urethane.  After three days of curing time, I plopped it on the post at the Toxic BBQ and had a pile of at least 50 caps by the time the night was through.  A great first run!

C3BO: Proof of Concept using Timbermanbot Schematic

This post is part of a series about building electro-mechnical PIN-cracking robots, R2B2 and C3BO.



This is a proof of concept for @JustinEngler's C3BO (https://github.com/justinengler/C3BO) using transistor controlled relays. It was prototyped by modifying Blink from the Arduino sample project.

The schematic was obtained from Timbermanbot (https://github.com/vheun/ArduinoPlays...) as seen on Hackaday (http://hackaday.com/2014/07/26/pwning...).

In the video, You'll notice I've replaced the touchpad for your finger with a wire to the headphone jack's ground as the circuit ground. The two pieces of copper tape were no longer sticky enough to stay by themselves, so I am holding them down. They press two and 5 with about 8 key presses per second.

OFBC: Putting it All Together

Note: This is part of the Project Write-up for OFBC: One Fluorescent Beer Coaster

After months of effort, we had a circuit, PCB and shell design to accomplish our goal.  Putting it all together meant solving some unique challenges in the home stretch.  By far the most communal part of the project was finishing the circuit.  Parts were bought by three different people.  It took hours of trial runs and four different nights in my shop to finally get the circuit assembled and ready.  In all, the project taught us to keep moving in spite of obstacles.

Internals

The main obstacle was PCB manufacture.  As detailed in that post, uncooperative copper and etchant lead to abominations not fit for solder.  Drill bits broke in PCBs, holes were misaligned, and traces were torn up as we worked and reworked the boards.  The major blunder was the reversed PCBs, but it was tempered by the lack of polar components.  Only the transistor and MOSFET needed to be adjusted when we realized our mistakes.  The quality checks and encouragement as we worked as a definite plus.  There were several times I wanted to just give up and abandon the project.  Truly, I get by with a little help fro my friends.

After the PCBs were in our hands, the task of soldering all the components was a team effort.  One person ran continuity tests on newly etched boards.  Another bridged scratches and pasted down traces.  Buttons (functional and fake) were inserted and crimped at one station while a fourth person began to solder on components.

That moment of truth when the LED lit up was breathtaking all nine times it happened.  When it, more often than not, didn't work on the first try, the scramble to troubleshoot was a team effort as well.  A loose connection, bad trace or through hole in need of a reflow was rooted out in minutes. I can't describe the feelings from closing the box with nine functional copies of the idea sketched out on a picnic table the year before.

Externals

Shell manufacture forced choices between what we wanted versus what we needed.  The mechanical ideas at the outset gave way to manufacturing considerations.  Features were pared back to match timelines, work schedules and summer vacation.  Anyone reading this who has worked in an Agile Development environment will recognize similar decisions they make every Sprint.  To borrow a cliché, "Perfect is the enemy of good enough."  With this in mind, we have an eleventh hour compromise ready: should the 3D printer prove a roadblock, we have arranged for a Wednesday night Hail Mary meeting to turn Ziploc Containers into eternal glory.

The Ziploc idea produced 4 "just in case" models.  We stabilized them with glass beads and hot glue.  The containers became the shell and mount for the PCB.  The beverage lid was provided by another ziploc container hot-glued onto the buttons.  Hot glue for grip and stabilization of the platform finished the job.  See the result in the pic below next to the finished shells.

Luckily, the 3D Printer roadblock was cleared just two days before the BBQ.  Poor quality filament lead to clogged extruders.  After a good cleaning, we were back in business.  5 shells total were produced with various upgrades.  We got a top that nested well with the shell, and the mouse-hole in the shell was added to allow the USB to be passed out of the body.  We did not get impressions in the top to get the lid closer to the lens of the LED.  We also did not get any part of the body held together by magnets.

Final assembly took place at Toxic BBQ itself.  The lights stayed on this year, but we started conversations and passed out some business cards with links here.  We placed a few on the tables farther out that didn't have light, and we presented two to the organizer in a Utilikilt.  Furthermore, it went on display in r00tz and the HHV for most of the convention.

Final Word

I left DEF CON for two years running with a profound sense of my own shortcomings.  I saw people around me doing amazing things, but I couldn't point to similar achievements for myself.  Though not terribly complex (most ideas came from Instructables, after all), the process and coordination required to pull off this simple idea has been eye opening.  It all started by pivoting from planning to doing.  It finished with an 80's-montage-worthy string of late nights and high fives.

Already, these efforts are fertile ground from which numerous other ideas have sprung.  Facing another DEF CON, I'm looking for the next big project instead of lamenting my noob credentials.  Only time will tell how many of these work their way to reality.

OFBC: Shell Fabrication

Note: This is part of the Project Write-up for OFBC: One Fluorescent Beer Coaster

Design

In parallel with the circuit, we designed an enclosure that would be more sturdy than hot glue and disposable containers.  The general idea was a shell with a lid that had some travel.  Our first designs focused on a mechanical clip to lock the lid in place.  Further ideas were a rail to keep drinks stead, a drain channel for condensation, and an interlocking base/top for easy stacking.  Our lack of expertise with the 3D design software and the complexity of the print made us go back to basics.

More Design Shots

Similar products used a coaster shape, so we started there. As the whole point of this project is to show off, we wanted to make it easy to disassemble top and bottom. To make this happen, we settled on magnets instead of screws for both top and bottom.

First Full-size Print (with Frenchman Mountain in the Background)

Problems

First, the 3D Printer needed to be calibrated, then the extruder needed to be cleaned, then the Kapton tape needed to be replaced.  After a much better test print, we got our first dimensional fit.  Once the PCB was together, we realized two things: 1) the buttons we bought had a much heavier mechanical action than the test buttons and 2) the LED package was too tall for the way we printed the top.  Combine the two, and a lot less light was reaching our girly drinks.  Something had to be done.  The above problems were noted, and various other edits were written directly on the 3D printed shell (a sharpie on white ABS works wonders for clarity).  They were handed off to our man with the printer while the rest of the team worked on PCB fabrication.

Between orders of Kapton Tape - Let's try Painter's Tape!

It was about 10% too small.  Looks like a job for Superm*n!

Not nearly as bright as it should be

Solutions

The final prototype came together the weekend before DEF CON.  Edits to allow the charging cable to escape from the bottom of the case, a drip cover to prevent condensation from entering the shell, more accurately nested tops and bottoms, and a host of other small changes came together for the final prints. In all, the first run is bulkier than we imagined, but we have discussed ways to miniaturize and reduce costs across the board.  It will be something we are proud of showing off.

The 3D printer was the final obstacle.  From miscalibration to a clogged extruder head to a stepper motor burning out, we had our fair share of problems getting the final package in a physical format.  If the repairs don't come through, we'll be manufacturing stand-ins for the Toxic BBQ.  Nothing can stop us at this point. 

The current Sketchup files will be available on the OFBC project on Github.

Great Size, Less Filling

OFBC: Random Design Shots

Note: This is part of the Project Write-up for OFBC: One Fluorescent Beer Coaster

Puzzling Out the Protoboard

Can you Smell the Confusion?

Shell Designs

Initial clip-together design with rails for stable drinks

Circuit, post and spring and modified clip-together designs

Hockey Puck design emerges, Boolean shape building discussions

First practical attempt at dimensional design

Space Hulk: Death Angel in a Cigar Box

The Plan

Space Hulk: Death Angel is a 1-6 player card game as brutal as its predecessor.  It has a ton of expansions, and it quickly outgrew its box.  I love to play this as a time killer while waiting for family or board game night to start.  It is brutal enough that it could be over in 5 minutes, but it is complex enough to withstand repeated plays.  I wanted a replacement box to be sturdy enough for for transport with the modern features of board game boxes that made parts easy to find and keep organized.  

I decided to go with a black Sancho Panza box.  After the labels were removed with acetone, I removed the inner lining and deororized the whole box with Odor-xit, an amazing oxidizer.  I lightly sanded the inside and blew it out, just in case.

Modern enhancements were card sleeves and push.pop style card storage.  Card sleeves let me play almost anywhere.  The Fantasy Flight sleeves were well matched for size.  The push/pop method of card storage was introduced to me with Lords of Waterdeep.  The insert in that game allows you the push down on one side of a deck of cards and pop up the whole deck at once.  No more groping in the bottom of the well for that one last card.  

Once I had my features, I sketched out a plan.  I calculated the height of the interior of the cigar box, and I left a little room for a rule book to sit on top.  The cards would be separated into six piles.  With the different expansions, this worked out pretty well.  Sleeved, only one pile gives me trouble and slips out regularly.  Each partition was made from 1/4" baltic birch cabinet plywood I had a sheet of.  This stuff is great for ripping into strips.  I used it on the Dominion Case as well.  I then notched the corners to make sure they fit in the box easier.  The final step was to cut slots into the horizontal divider and a single slot in the vertical dividers.  This was mostly done by feel.  I cut the outside edges, cleaned up the center and tested the fit.  This was repeated until I was satisfied.

Overall, the box had dramatically improved the portability of the game with all its expansions.  The box complements the game itself in its simplicity and order.

Lessons Learned

1. I did not leave room for the rule book at first.  I had to chop down the height of the dividers once I realized the oversight.
2. I originally slotted the vertical dividers x 2 on the wrong side of the measurement.  This left half of the cards with a much tighter fit.  It took me a it to figure out what I'd done, and I was unable to salvage those dividers.  When making cuts in "The Middle", ensure you have things in the exact middle by flipping your pieces around once they have been marked.  The middle should be in the same place on both pieces.
3. Removing the exterior lining may not have been the best way to do things.  The biggest problem with this box is that the cards will slip out through the gap between the lid and the bottom.  Moving the push/pop dowels to the outside edge could fix this too.  The sleeves would probably need to come off if the second option was used as the interior would lose 1/16" on all sides.
4. Salvaged cigar boxes need better hardware.  Especially when transporting them, it is important that all components remain secure.  A swing latch could greatly increase the ability to keep the lid closed beyond the simple latches on the cigar boxes.  I'm going to pick some up and make some recommendations in a future post.

DnD Table 3 and 4

Preamble

Our gaming table has gone through many phases.  The first was an 8x4 foot sheet of plywood on some sawhorses.  We wrapped it in felt and stapled it down, but the felt kept pilling and it was hard to replace.  We chopped it down to 6 feet, split it down the middle and swapped vinyl for felt, but the legs were still hard to store.  The third mod was to replace the cumbersome legs.  The fourth was a new and lighter table top.

This has been useful for gaming, crafts and many other activities.  It is light weight and takes up very little room.  We keep ours in the garage and pull it out when we need it.

The Legs

Lowe's had some really nice seasoned 2x3's.  A few hours and chop saw got me a new set of legs.  The chief features of the table are its simple construction and plentiful leg room.  It has been a chore to find a good way to attach the top to there, however.  Overall, the legs have been maintenance and trouble free.  If I borrowed the design from somewhere, I have forgotten it.  If you attempt to replicate it, read all instructions first, measure twice and cut once, and always wear your safety glasses.

The cut list is basic and can be created from six 8 foot 2x3's, Not compound angles are needed, but the legs have angled cuts.  The measurements below rely on the geometry of your lumber being moderately predictable: Two 2x3's together should come out to 3 inches.  You may have to adjust the length of your interior cuts if this is not the case:

• Outside Length: 72" x 2
• Inside Length: 69" x 2
• Outside Width: 27" x 2
• Inside Width: 21" x 2
• Legs: 30"+ x 4
• Blocks: 4 1/2" x 2 1/2" x 4 (mine are from oak as that's what I had lying around)
• Lots of 2 1/2" construction screws
• 4x 5 1/2" Carriage Bolts with Washers and Nuts

Assembly of the top is also basic.  Remember to drill pilot holes for all screws ans work from the inside out:

1. Inside Width -> Inside Length 
2. Inside Length -> Outside Width
3. Outside Width -> Outside Length

The legs can be tricky to position depending how high you want the table top.  For my 24" height top, the legs are 26 1/2" with a 75 degree cuts at both ends (making a parallelogram and not a trapezoid).  The legs meet in the center of the table top.  The math to place the hole precisely has been lost, but those inclined should have no trouble replicating it.  In general, slip your uncut legs into the slots between the Inside and Outside Length so that they meet in the middle.  At a point between 9 and 11.5 inches from the end of the table end, drill the hole for your carriage bolt through both Inside Length, the Leg and Outside Length.  Make sure the hole is not closer than 2 3/4" from the end of the Leg.  Thread the bolt through the hole and test your leg height.  Cut your leg into a parallelogram to maximize contact with the floor and minimize interference with the table top.  Position the Blocks to ensure the legs only rotate a certain amount.

If all goes well, you should have a sturdy and light set of legs to use as a base for any table top you can dream of.  The method of attaching the top to the base is discussed in the next section.

The Top

The latest addition was a lighter table top.  Previously, we used a piece of 3/4" Oak Plywood with vinyl stapled to it.  This was extremely sturdy and stable, but it was a huge pain to move.  I designed the new top to be light and attach directly to the legs.

Much like the legs, the top was stick framed using flashing from Lowe's.  This time, 1x2's provided a good base, and Kreg Pocket Hole joinery held everything together.  Along the center line, two lengths are abuttewd to provide enough surface area for the hinges.  Instead of heavy plywood, I used a thin luan top.  All this was wrapped in vinyl again (the most successful table covering we've had thus far).  Unlike previous folding incarnations, the vinyl was split in two pieces and each half of the hinged top was wrapped separately.  The cut list for my 6' 6" top is below.  The Inside Stiles are not required to be the listed lengths as long as their total lengths come under 72".  I placed them so they would fit between the blocks in the legs and help the top align to the legs.  Your mileage may vary; see lessons learned below.  As always, your local dimensional lumber may vary, measure twice, cut once, and always wear your safety glasses:

• Outside Stile: 78" x 4
• Rail: 19" x 8
• Inside Stile (Ends): 17 7/16 x 8
• Inside Stile (Center): 37 1/8" x 2

Assembly is a little trickier than the Legs.  With your pocket hole jig, join the Outside Stile to the Rails at both ends.  Use the Inside Stiles to locate where to place the inside Rail.  Add the Inside Stiles to make a double-layer of wood in the center of the table-top to better brace the hinges.

With two halves of a table top in hand, it is time to locate the hinges.  Match the hinge location to your legs so they won't interfere with how the table sits flush.  The vinyl wrapped on the side that will be the center of the table will need to be relieved where the hinges will go.  I chose to wrap after attaching the hinges.  I now feel this was a mistake. In the pic above, I've routed out a place for my hinges.  In practice, I didn't need to do this.  Just clamp the table halves together after the vinyl is in place, locate your hinges parallel and centered on the joint and screw in place.

I have tried many things to secure the table top with a minimum of fuss.  Right now, I'm using machine screws and associated sockets sunk into the top.  The screws thread through the legs and into the top.  They require climbing under the table.

Lessons Learned

1. I would decide on a method of attaching the table before I started building.  The primary candidate is a Sash Lock.  Placed correctly, it would easily lock the legs to the table top without climbing under each time.
2. I would avoid insetting the hinges.  Instead, careful placement would allow the hinges to be used without interfering with the mating of table top and legs.
3. I would wrap the vinyl completely around the top so all stapling was done on the bottom.
4. I would not tell my gaming group how much better this version of the table was until after it had proven itself.  I have gotten no end of grief every time I climb under it to hook the two together.  What are friends for, eh?

Bonus Shot: Plans

Updated: Random Shop Projects

Cat Tower

We needed a new cat tower due to acquiring a monster of a tom.  Might as well do it right!.  I wrapped the columns in sisal (one roll of Lowe's Blue Hawk lasted about a foot and a half), made the base double-thick plywood, and wrapped all horizontal surfaces in carpet.  There are a brazillion staples in that thing.

I wish I had purchased round posts instead of these ungainly square ones.  Not only were they more difficult to wrap, but the sisal seems to pull away and tear easier when it sits a quarter inch from the surface in the middle of each face.  The next model will have pillars, and I have half a mind to glue the sisal in place to lengthen the time it takes to get into such disrepair.

Update: I made a small tower for upstairs and glued the sisal in place.  It seems to be holding up much better over time.  Instead of using square pylons, I used redwood ties from Lawn and Garden.  They wrapped much nicer than the square ones.  It is held by a single bolt and, as of this writing, has broken once when someone fell on it.  Eep!

Vacuum Tool Holder

This serviceable Shop Vac tool holder plan came in via Shop Notes.  The tools are sitting atop PVC end caps of a fitting size.  It took longer to find the parts than it did to assemble the thing.

Miter Sled

Shop Notes, Woodworking for Mere Mortals and a bunch of Indian Rosewood acted as a catalyst to get me to build a Miter Sled.  I hate miters on a contractor's chop saw.  The constant adjustment leads to endless headaches.  The sled eliminates this with a stable 90 degree platform that facilitates perfect cuts every time.

The base is plywood, and I followed the techniques of the above YouTube video to get my rails aligned.  To each arm, I added T-Track and will build stop blocks.  These will be invaluable for building boxes and lots of picture frames in the same size. 

Now all I need is a spline jig that stands the miter on end and allows reinforcing slots to be added...

Bonus Shots

Miter Sled Plans

Garage Shelves Plans

Bitz Wall for Blue Table Painting 

Page 2

OFBC: Design and First Prototype

Note: This is part of the Project Write-up for OFBC: One Fluorescent Beer Coaster

Circuit Design

I began the search for parts to fit the Instructable, and I realized I had a lot to learn about each part.  To match the circuit, we searched Frys, Radio Shack, ebay, Mouser and many others online. For an unproven design, going with an unknown module and supplier wasn't an option. Instead, we found all the components we needed on Adafruit.

• Lithium Ion batteries must be matched to their charger to avoid dangerous heat and combustion incidents.  Capacity is determined by the Amp-hours rating.  The LEDs I was targeting were a max of 350mAh, so I looked for batteries had to be over 1000mAh to get the targeted 3 hour run time.
• The charger choice was mostly driven by battery choice.  We didn't feel like we could provide a mounted Micro-B port in the time available, but a charging circuit mounted to a full sized USB plug was a good substitute.  With the shell, we would provide an easily removable bottom and 'mouse hole' to allow the charger to live outside the case.
• Most LED projects online mention heat at one point or another.  To get ahead of this concern, we opted for a heat sink-mounted super bright LED.  This same LED bead was seen on ebay without a heat sink, but we didn't want to screw anything up due to inexperience and opted for the more expensive package for the first run.
• The Driving Circuit was a simple buy, and the choice also dictated our resistor purchase.  The key value from the MOSFET we purchased was Gate Threshold Voltage.  The voltage drop across R2 with the battery we bought had to match this value.  Using V = IR, R = V/I = 1.5V / 350mAh ~ 4 ohms.

Materials List

Name	Description	PID
Battery	Lithium Ion Polymer Battery - 3.7v 1200mAh	258
Charger	Adafruit Micro Lipo - USB LiIon/LiPoly charger - v1	1304
LED	1 Watt Cool White LED - Heatsink Mounted	518
Driving Circuit	N-channel power MOSFET - 30V / 60A and NPN Bipolar Transistors (PN2222) - 10 pack	355 and 756
Resistors	100K and 3.5 Ohm Resistors	Already Owned

Components, Breadboards and Protoboards, Oh My!

Once the materials were in hand, the breadboard went well.  It worked the first time!  While we waited for batteries to charge, we used a simple brick of 4xAA batteries.  The beauty of the driver we chose is that it can drive LEDs using any voltage source over the target voltage.

Using the breadboard and schematic, we attempted a protoboard version of the circuit.  This was a complete mess, and it took us a lot longer than it should have.  However, by the end of a single prototyping session, we turned a jumble of components into a working light.  One high/low note happened when we wanted to minimize the number of connections but didn't have the right resistor for R2.  We twisted two resistors together to get close to R2's 3.5 Ohms and put them through the same hole on the protoboard.  Instant parallel resistor!

Conveniently, the whole project fit under a Ziploc Container lid.  A little bit of hot glue, another section of protoboard with a hole in the middle, and charged batteries got us our first complete prototype!  It was brighter than the equivalent cell phone flash and had excellent diffusion through some purpose-bought Smirnoff Ice.