[Food] – Proto A cold smoker, DIY bacon

Posted on 2011.01.05 by ttstam

Apparently, Weber-Stephen Products LLC does a really, REALLY good job with their enamel coating. My buddy Jared called and reported that even after half hour of attacking the metal with an agressive angle grinder, the coating held on tight.

So he ended up riveting a section of the exhaust pipe in place.

I then attach a 25ft x 3″ dryer hose to the exhaust pipe, using hose clamps. On the “protein box” side, since it doesn’t get hot, the quickest way to prototype up a door was to cup apart a shipping carton for corrugated cardboard, and duct-tape it in place. To draw the smoke in , I gimped up a computer case fan and some D sized batteries for a 12V power supply:

(Even with sealing the battery holders in a bag, the smoke still got through and scented the batteries. Nothing a good scrub can’t handle, but I am glad I didn’t put my 7Ah NiMH cells in there!)

Computer fan after a 12 hour smoke. Still runs, no binding on the bearings, but I won’t be using this for mission critical cooling for sure…

With the outside temperature below freezing, food spoilage and temperature control in the protein box wasn’t much of a problem. I fired up the hot side of the smoker with half a chimney’s worth of lit mesquite charcoal, piled on the wood chips and closed the vents.

Immediately, thick, white smoke started pouring into the protein chamber. w00t!

Now, the pork belly had been pre-cut into roughly 1.5lb slabs, and these are loaded onto the rib rack for a nice long 8 hour soak in the applewood smoke:

In my haste gimping this together I forgot to check the grain of the corrugated cardboard. If you look closely you can see the scoring I did with a box cutter to allow the cardboard to bend.

Note that there’s almost no leak from the smoke generator side:

For just 3 rivets and angle brackets, Jared did a really good job attaching that pipe. (Since this is the hot side, and since we are essentially vapor-treating the food in the protein box, I’ve decided not to try for a perfect seal with JB-Weld or Silicone. I don’t want degassing JB Weld in my bacon).

After 8 hours, the bacon was removed, slightly frozen, then taken to my local artisian butcher’s for slicing on their meat slicer. It pays to have good relationship with your suppliers.

This package is headed for Hong Kong via my Mom to my Uncle’s family.

From my buddy MikeZ’s report that his fridge smells like it had barely survived a house fire, it would appear that the bacon “degasses” after it’s been smoked. We are still evaluating whether the smoke and brine flavor mellows out over time – if the remaining bacon lasts that long in his fridge.

I guess we’ll have to make more to try… stay tuned for more experimentation to come.

[DIY] – 3D Camera Rig

Posted on 2010.07.20 by ttstam

I’ve really been lagging on my blogging. Here’s a quick update.

I’ve recently found myself working out of the Beaverton office again, so late one night after finishing up I hopped onto the company’s aging, crusty lathe:

These are custom captive screws for the Benro quick-release plates I picked up in Hong Kong. I’m mounting the Benro plates to a piece of 8020 1010 extrusion, and the T-slots are a little bit deeper than an ISO standard camera mount. So, for my application, a custom screw would be needed.

I’m actually pretty happy with how this turned out; the machine is old and the hand-ground parting tool isn’t the best for cutting stainless steel.

To chuck the screw into the chuck without damaging it, I took a page from an old machinist trick of slotting a nut with a hacksaw and clamping it in a 3-Jaw chuck. I started with a 1/4-20 x 0.5″ SAE button head socket cap screw.

(Note: Yes, I am aware that the standard tripod thread is a 1/4-20 British Standard Whitworth – cut with a 55 deg angle instead of a 60 deg angle. I challenge the reader to find one here in a hardware store in the good ol’ USA. A 60 deg SAE thread is “close enough” for this application with some very minor interference)

The resultant screw is a bit too long, so I trimmed it down a little bit with my motor tool.

The tool is a Taiwanese made version of the Foredom – a 600W motor on a flex shaft and a foot pedal for actuation. It takes all the standard Dremel accessories and it’ll slice through stainless pretty easily. I lined the jaws of my Wilton vice with some engineering paper scrap, and used my pano clamp as a clamping base for the tripod plate. Then, using another machinist’s trick, I put a nut on each of the screws to be cut. When removing the nut, the nut acts as a tap and cleans out any debris on the screw threads and restores the proper thread form.

And BTW – at 20,000+ RPM and with 600W of power behind the disc – any slip up is … painful. Warning: somewhat graphic picture ahead:

The wound looks A LOT worse than it actually is. I think the heat from the abrasive blade cauterized the wound – it didn’t bleed much. Digging all the abrasive grit out under running water was a different story – good reminder to be more careful the next time.

And here’s the finished rig! Now, I need to order some 3D glasses…

[Engineering] – Bullet Flight Sensor, Systems Integration

Posted on 2010.01.22 by ttstam

Quick status update on the bullet flight sensor. This is heading into systems integration testing next, where I’ll be firing up each section of the circuit and making sure it all works. Missing is the break beam sensor that I put a air rifle round through by accident

Note the “unusual” arrangement with the pocket wizard. The “hot shoe adapter” is actually plugged into the sensor to simulate a camera’s hotshoe firing the pocket wizard.

[DIY] – Photo Chemical Machining

Posted on 2010.01.22 by ttstam

An old joke, from my college days:

“Do you know how you tell the difference between a Chem student and a Physics student?”
“The Chem student washes his hands *BEFORE* he goes to the bathroom”.

There’s some truth in that statement, especially with regards to corrosive chemicals…

Tonight I decided to give the toner transfer photomachining process another go. The toner transfer material is from PulsarFX and purchased from DigiKey Corp along with the rest of my electronics components for the bullet flight sensor and … some other projects.

First, I did up the “photo mask” in Adobe Illustrator. Since the toner side is face-down on the etch surface, I do a “transform – flip” operation to mirror the text:

Top to bottom are: plain paper proof of the printout, plain paper proof of the inverted mask, and the actual mask itself, on the toner transfer paper. At a buck something per sheet, it’s advisable to do a plain paper proof every step along the way

The toner transfer paper works by heat and pressure. They sell a unit for doing this, but I am not about to spend a few hundred bucks on a special laminator. So I liberated the clothes iron and set it to linens, and tried my hand at ironing on the transfer:

Well, bummer. I had cleaned the brass piece with my Festool random orbital sander with 220 grit sand paper. Turns out a brillo pad works better.

If at first you don’t succeed, try, try again, and try harder:

My Dad would call this “paying tuition”.

After playing around with different methods of applying pressure, I finally got something good:

And a piece promptly flake off as I start blotting the workpiece dry. (the paper is dextrin coated, and releases after sitting in water a little bit, kinda like a water-slide decal).

After about 45 minutes in the ferric chloride (yeech!) etch tank, this is what I managed. Not acceptable, but at least I have an idea that the system works. Kinda. The etching is about 0.2mm deep. The design intent had been to sand to the black (raised) border, then fill the inside etched area with an ink, leaving the brass text raised against a black background. The piece would then be matted into a framed artwork along with the panorama being presented.

(For now, I’m just going to stick to my wax seal and signature, thank you very much.)

(This is “R&D”. Failures are not unexpected; what’s important is documenting how things failed, and learning from it.)

[Engineering] – Bullet flight sensor – circuit design

Posted on 2010.01.17 by ttstam

Continued work on the bullet flight sensor electronics. Dad had suggested that I research a “monostable vibrator” circuit, and to look at the 555 timer IC, so after some tinkering and math, here’s my first draft circuit diagram:

Dad (a retired electrical engineer) had given it his blessing, so the next step up would be physically prototyping it. Looks like I’ll be placing an order with DigiKey or Jameco or some other online electronics component vendor.

While the circuit components are enroute – and they will be breadboarded up first – I’m going to try my hand at learning Eagle, a CAD design software. The circuit is simple enough that I can probably etch it myself using laser transfer paper, but I might also just job it out to someone like BatchPCB.com and deal with it that way. It’ll all depend on the mechanical fabrication lead time as well as other project loads.

Meanwhile, mechanical design needs to be refined a little bit. These are current CAD model screenshots:

Bullet_Switch_Assembly.PartialDisassembly

Here the unit is partially disassembled to change batteries.

Here’s a top view looking straight down on the circuit card, with the detector barrel rendered transparent.

And finally an isometric view of the unit assembled.

Mechanical details for the battery contacts, as ewell as lead-in for the slots, needs to be integrated. Then it’s a matter of generating a file to drive Dave’s grandparent’s laser engraver to cut these acrylic parts!

W00t, can’t wait!

[Fail] – Toner transfer for “photo”-etch

Posted on 2010.01.14 by ttstam

Well, no project always go 100% smoothly, and the important thing when one fails, is to document the failure.

Tried to use a toner-transfer method to do a photo-resist mask tonight, to chem-etch a brass face plate for a couple of pieces of photography that I’m framing up for presentation / sales. I’ve done this before in college doing DIY PCBs and earlier on in high school for model airplanes.

The process involves mirror-inverting a photo negative of the mask pattern and then printing it out on a photocopier. Because toner is a thermoplastic, a regular clothes iron can be used to remelt the toner and transfer it to another medium – balsa wood for cutting (this is before laser cutters) or, in my case, a sheet of brass plate from K&S Engineering in Chicago for a name plate.

Turns out I forgot that you need special paper. Toner sticks really well to regular paper (no surprise):

Oh, and it helps to turn the steam off on the clothes iron.

I think this is the stuff that I used in college. I’m placing an order tomorrow for a small sample, shipped pony express (ground) from Florida. So, check back in a week to see how it went.

[Engineering] – More bullet sensor validation testing

Posted on 2010.01.13 by ttstam

Tonight, I did more engineering validation testing of the IR breakbeam sensor mentioned in the previous article.

First, the setup. The sensor is securely mounted in my benchtop vise, with a phone book propped up behind the bullet path as a pellet trap. (Finally, a good use for those dead-tree edition phone books!). A regulated DC power supply is used to provide the power to the sensor module, and my oscilloscope is used to monitor the signal line. As before, we set the oscilloscope to trigger on a falling edge signal at a level close to DC Bus -.

(I need to get my garage sale O-Scope probes checked. They don’t seem to be reading the voltage right, but at least the signal generator test indicates a good test pattern. Probably something stupid I forgot to set in the software. I’m still learning how to use this thing).

Next, I set the oscilloscopes time scale to 100 nanoseconds per division. Yup, definitely picking something up! That’s a good sign. Rechecking at 1 microsecond per division shows a fairly clean signal.

To give Dad a good idea of what he’s engineering to, I need to take some measurements of the pulse width of the event. We’ve previously calculated about 18.3 microseconds for a round ball at 1000fps. (Note that we actually don’t know how fast the air rifle is shooting at, nor is the pellet perfectly round.)

Look at that! 20 microseconds. Love it when the calculations matches real life data.

The next shot clocked in at a mere 5 microsecond pulse. There could be 2 reasons: A) the angle of the flight path through the sensor might be changing, or I might be nicking the beam differently. Still, the oscilloscope clearly captures a 5ms pulse.

Another shot, this time generating a 10ms pulse.

Yet another 5ms pulse again – followed by a lot of electrical noise. That’s strange…

Looks like the round nicked the sensor housing. Yeah, that would explain the sensor noise.

Remarkably the sensor still works. Putting the gun aside, I grabbed the soldering iron sponge and started dripping water past the IR beam. It registers on the O-Scope! (translation – this can be used for those awesome water-drop shots!)

Finally, here’s a couple of pellets recovered from the phone book. Love how you can see the rifling marks on the pellets .

[Pranks] – Difference between a cool job, and an AWESOME job

Posted on 2010.01.12 by ttstam

You know what the difference between a cool job and an awesome job?

When you have a bunch of coworkers that relies on wit to prank each other. Better yet, when you can prank your boss, and he appreciates it.

Jared, the other Mechanical Engineer at my day job, also has a side business, building parts to soup up Evos. (Peeps, go over to his website, Binary Engineering, and give him some web love). Recently, to advertise his car, and his mad engineering skillz, Jared got a vinyl plotter.

Used to be that if you wanted a vinyl plotter, you were stuck with a Roland or Summa. These are the 800 lb gorillas in the vinyl plotter world – expensive, well crafted machines.

But if you think about it, a vinyl plotter is just an X-Y plotter with the ability to lift and lower a swiveling tungsten carbide blade. And the stepper motors and drivers required to drive such a system had come down drastically in price lately.

Enter the joys of Chinese manufacturing, stage left. Now, for < $400, one can buy a 24" wide vinyl plotter. The software's not as refined, and the cutter is a loud, cheap, affair - but it gets the job done.

And of course, what do creative engineers do given a new toy? They find a way to prank someone.

Here's a caricature of myself I found at my desk when I came in Monday morning:

And here’s a new door decoration for my boss. He owns a Harley, so we have a feeling that this one’s gonna be up on his door for a while

[Engineering] – Testing of a Break Beam sensor

Posted on 2010.01.12 by ttstam

Today, I performed validation testing of the breakbeam module selected to handle bullet-detection for high speed photography. The sensor module is a Sharp GP1A57HRJ00F from SparkFun Electronics (Datasheet). This is an infra-red emitter / detector combo: one half of the module holds an IR LED, the other half an opto-transistor detecting the output.

The output on Pin 2 is at TTL High until the beam is broken, then it goes to TTL low.

I wanted to make sure the sensor does as advertised (remember, I’m a mechanical engineer by trade, that happens to dabble in electronics and coding). So I hook it up with a breakout board and populated the current limiting resistor with a SMT 231 ohm resistor that we’ve got lying around the lab. Here’s the schematic:

Connecting Vcc to a 5V DC power supply in the lab, and connecting a probe from an oscilloscope between SIG and GND, I was able to get the following response:

As you can see, the output on the signal switches rather quickly. The oscilloscope was set to trigger off the falling edge of the signal at approximately 3.8V and the drop in voltage occurred within 20 *nano* seconds.

If we assume a .22 round that’s spherical in shape (say, a BB), travelling at 1000 fps:

Each milli-second the round covers 1 ft
To cover .22, or 0.0183ft, the round will take 0.0183 millisecond, or 18.3 microseconds.

I’m fairly confident that the round firing through the beam can trigger an electronic response. The next challenge is then designing electronic circuit to lengthen this response to a switched pulse to fire a pocket wizard radio transmitter.

[DIY] – Canon 580EXii repair

Posted on 2009.07.10 by ttstam

Broken flash tubes are one of the most common ways a flashgun comes to an early demise. Unfortunately, the cost of professional repairs often make repairing a strobe a unfavorable proposition – at $150-200 minimum labor charge, often just for diagnostics alone, repairing a flash would costs about the same as buying a new one. In this installment of the TwinGeeksPhoto.com blog, I’ll show you how I repaired my 580EXii flash gun so that Rachel can take two eTTL capable flashguns on her trip to the UK.

Before we proceed further, do understand that a standard hot-shoe powered flash gun contains high voltage components. A 300mA jolt across a human heart is enough to induce fibrillation and cause the heart to stop, and the photo flash capacitor in a flash gun has more than enough juice to do this under the right conditions. In other words: THIS CAN KILL YOU. Perform these repairs at your own risk; we are not responsible if you kill yourself.

Years ago, when I was in primary school in Hong Kong, my Dad gave me an Olympus Stylus range finder to learn photography on. It had an external clip on flash, powered off a single AA cell. One day, after watching the Batman movie, I decided I wanted to build a bat signal, and a good way to do so would be to use the flash. I correctly hypothesised that the two recessed metal contacts on the side of the flash were used to trigger the flash, and also correctly deduced that shorting those two pins would cause the unit to fire. When I proceeded to short them out, with 2 sewing needles pilfered from my Mom’s sewing kit, the flash fired – and sent me across the room. I had made a potentially fatal mistake of holding one needle in each hand, and as such the electricity went through my chest. The resultant chest compression was so severe that it (combined with the impact of hitting a hard wood floor) knocked the breath out of me. Had that been a Metz potato masher, I might not be around today.

That little story out of the way: let’s get started.

Parts needed:

Flash head: The 580EXii’s flash head subassembly is integrated with the zoom motor and the high voltage ignition coils. This makes repairs more expensive, but on the bright side, there is no high voltage soldering involved. The part # from Canon is CY2-4227, and at the time of writing, US$63.23 from Canon Parts Service. You can contact Canon Parts Service directly at: +1.732.521.7230.

Silicone oil: The 580EXii is weather sealed. This is accomplished by a special molded O-ring like gasket. Over time, and after disassembly, this gasket material loses its sealing efficiency. To get around that, I wet my fingers with medical-grade silicone oil and lightly oil the gasket on reassembly.

Medical grade silicone oil is often sold and marketed as “Water proof sex lubricant“. And, yes, that’s really what I purchased it for – my bottle is quite a few years old and very much unused…

Tools:

Any well stocked DIY maker type should have the following tools:

* Jewelers’ screwdriver set. I highly recommend Wiha tools – they are German made out of Vanadium tool steel. The set from my college days still works beautifully. Local in Seattle, Hardwicks & Sons carries them.

* Optional: A “spudger” – often an engineering plastic pry bar, for prying apart the plastic casing. I actually don’t own one; it’s next on my list (I’ve been making do with dental picks…). You can buy them from iPhone / iPod repair stores, such as www.ifixit.com

Let’s get started:
IMPORTANT MESSAGE FROM OUR LEGAL DEPARTMENT: THE PHOTOFLASH CAPACITOR IS CAPABLE OF HOLDING A POTENTIALLY LETHAL CHARGE FOR A LONG TIME. AS IN, DAYS. OPENING THE FLASH WILL EXPOSE YOU TO A SHOCK HAZARD. YOU HAVE BEEN WARNED. PROCEED AT YOUR OWN RISK.

There. Now, take the jeweler’s screwdriver, and remove the screws shown. For the screws hiding under the cosmetic santoprene trim plates, carefully remove the trim by inserting a screwdriver or spludger down along the edge of the trim piece, then gently prying it up. The die-cut adhesive tape will lift out with the trim piece.

Next, with a flathead screwdriver, gently press down on the plastic spring clip on the swivel button side of the flash gun. This unclips the two halves of the upper flash head enclosure.

Don't use excessive force!

Observe that there are 4 wire bundles coming into the flash head subassembly. A larger ribbon cable carries the command signals as well as power to the zooming flash head, while a smaller, but much thicker gauge cable carries the actual lines for firing the flash. THESE LINES ARE CONNECTED TO HIGH VOLTAGE AND CARE SHOULD BE TAKEN WHILE HANDLING THE UNIT. At this stage, the voltage is probably ONLY 300V or so; it is enough to give you a very nasty shock. Off the coils, however, the voltage can be in the kilovolt range, which will paralyse muscles.

HV and control cable bundling disconnected for clarity. Note the flex circuit ribbon entering the flexible printed circuitboard assembly for the flash head subassembly, about 9o'clock position to the copper coil. Do not damage the connector / ribbon cable!

Standard procedure, for anyone who’s ever worked with high voltage, is to discharge though a 1 megaohm resistor. Most people don’t have a 1 megaohm resistor, so you can *carefully* short the contacts with a screwdriver with an insulating handle. Sparks could fly when you do this, so be warned. (In my case, I havn’t had batteries in this flash for over a year, so no fireworks. Still, I shorted the pins just to be sure.

Molex (tm) connectors for the high voltage cabling assembly. Don't touch the solder ends without discharging the capacitors first ... it hurts.

Next, disconnect the molex connectors. A spludger works; I used a flat jeweler’s screwdriver to carefully pry them off.

The two other wires that are attaching the flash head are the following: A small ribbon / flex circuit to the flash head’s flex PCA, and what appears to be a grounding, conductive plastic wire of some sort to the polycarbonate housing. Remove these. Remove any excess glue on the black grounding wire. You will tape this back in place with scotch tape. Pay attention not to pull too hard on the flex, those suckers are delicate.

Now, remove the 2 black screws holding the white polycarbonate housing. The fresnel lenses will probably come out too. Note the orientation and order of the fresnel lenses; the gasketed lens is in front with the ridges facing out.

This frees the flash head subassembly. Replacement is in reverse order, for the most part. Don’t touch the flash tube, or the output glass – oil on fingers tend to shorten lifespan of these components. I found it easiest to tape in the black grounding wire, then the power and signal cable bundles, then install the subassembly into the housing with the two screws. Finally, carefully hook the hole in the flex circuit connection with the end of a toothpick and slide the connection into the mating connector.

After the connectors are in, reinstall the fresnel lenses. I use a little bit of waterproof sex lube silicone oil to lubricate the O-Rings, so that they maintain their weather sealing.

Reassemble in reverse order and test. Voila!

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