MightyOhm » Electronics

A glimpse at Electronics Workbenches around the world…

Jeff — Tue, 24 Jan 2012 21:45:00 +0000

Since creating the Electronics Workbench Flickr group last November, I have received lots and lots of really amazing submissions from electronics hobbyists and professionals around the world.

My two biggest takeaways so far? I do not own nearly enough test equipment, and my shop is not nearly as well-organized or space-efficient as it could be (I need to use all available wall space and build up).

Here are a few of my favorite images from the group:

Click any of these images for a larger version!

Joe Grand (of Prototype This! and Grand Idea Studio) and his awesome electronics workshop:

(Nice scope, Joe!)

blalor turned his BMW into a temporary workshop, and his passenger seat is the electronics workbench (note the laptop perched on the dash):

eschlaep (Eric Schlaepfer of tubetime.us) submitted this moody shot of a CRT project in progress:

Senke2 has a nice home lab with a lofty feel:

Looks like *someone* has a Tektronix fetish. Beautiful setup by Alan (W2AEW):

More scope envy, of both the oscillo- and micro- kinds (Thanks Mgburr!):

embeddederic sent in this picture of his workbench. Note the Tek 491 spectrum analyzer up top, 10MHz – 12GHz with 1950s(?) technology:

And lastly, check out this awesome workbench panorama by anachrocomputer (best viewed large):

See if you can spot the Tektronix 575 curve tracer!

There are lots more great photos in the group photo pool.

Do you have an electronics workbench that you’re proud of? Snap a photo and share it with the group!

New Flickr Group for your Electronics Workbench

New Flickr Group for your Electronics Workbench

Jeff — Sat, 19 Nov 2011 00:03:44 +0000

Ahh, the electronics workbench – shrine to the electron, the diode, the transistor, the soldering pencil and flux pen.

You can learn a lot about someone by looking at their workspace. Note the way that they store components (in pullout drawers or plastic organizers?), hang test leads (on hooks or wire racks, or on a nail?), and keep spools of wire at the ready for repairs and new projects.

A look at someone’s electronics workbench gives you a small glimpse into what is usually a fairly personal space – a space where visions become reality and electronics projects are brought to life.

While there are quite a few electronics workbenches on flickr, I determined after a quick search that there had been no attempt to bring all of these glimpses into a hobbyist or engineer’s soul together into one place.

And thus was born the Electronics Workbench flickr group:

Have a photo of your bench? Add it to the group!

No? Then go downstairs into your basement, out into your garage, or up into the attic and take one!

And don’t spend too much time cleaning it up first – noone will believe you that your workbench is that clean when we’re not looking.

Also, a shoutout: This group was inspired in part by the Workbench of the Week (WOTW) page over at The Amp Hour. I don’t think WOTW has been a feature on the show for several months. Maybe we can get Chris and Dave to bring it back??

Happy soldering!

- Jeff

www.flickr.com

SurplusGizmos

Jeff — Fri, 18 Feb 2011 05:04:59 +0000

While I was visiting Portland last month, I made a quick stop at SurplusGizmos in Hillsboro.

SurplusGizmos is what an electronics store should be, and it’s the kind of place that I love to visit. It’s also the kind of electronics store that is completely nonexistant in Austin (oh, my beloved HSC, how I miss you), but I digress…

You can usually tell a good surplus electronics store by the pile of junk outside the door (usually with a sign on it that says “Make Offer.” I’m not kidding:

Inside SurplusGizmos, you’ll find aisles full of electronic components like resistors, capacitors, connectors, random semiconductors, fans, motors, and miscellaneous surplus stuff. Paradise!

AVR microcontrollers! Forrest Mims books!

They have cabinets with drawers full of electrolytic capacitors! Yes! This is what a real electronics store is like!

This way, resistors by the foot!! This ain’t no Radio Shack!

Aluminum by the pound!

Interesting pieces of surplus equipment sold for pennies on the dollar!

They have a huge selection of “solder samples”, printed circuit boards that are used to…

Actually, I’m sure what they are for. I think they are used by the PCB manufacturer to test their process, but can someone comment about what solder samples are for, and why you always get one or two when you order a full panel of PCBs?

Anyway, there were LOTS of them. Hundreds. Looking at these panels reminded me of Dave Jones’ PCB Design for Manufacture video. Lots of examples of v-scoring, tab-routing, fiducials, etc.

I picked up a few to use as coasters/wall art/whatever.

Apparently SurplusGizmos has some deal with Oregon Scientific and gets customer returns of their weather monitoring equipment. It seemed like if you spent the time to collect all the right parts, you could build a complete indoor/outdoor wireless weather station for a fraction of the new cost.

I wish I could have spent more time there, but my time was limited and my luggage space was small. Next time!

If you’re ever in the Portland area and want to see what a “real” electronics store is like – check this place out.

I took lots more photos, many of which are available on Flickr.

Oh, and SurplusGizmos is listed on the surplus electronics wiki. If there’s a good electronics store in your area and it’s not on the wiki, add it! Help keep these small, independently-owned electronics shops alive!

Surplus Electronics Wiki Growing Fast

Jeff — Wed, 07 Apr 2010 20:33:06 +0000

The past few weeks have seen a lot of activity on the MightyOhm Wiki!

Since it was mentioned on the Make: blog last week, helpful readers have been making significant contributions every day.

One highlight of the wiki is the Surplus Electronics Resources page, which I first posted about in February. It has more than quadrupled in size since then and now includes surplus shops in the United Kingdom and Canada in addition to dozens in the United States. If you haven’t seen this page yet, you should definitely check it out.

If you don’t see your favorite electronics surplus store on the list, please add it! Several of these “junk shops” close every year due to rising rents and competition online. Anything we can do to keep them in business will benefit the maker community. One way to do this is by making sure that folks know that these resources exist, and this is where I hope the wiki will help.

I want to express my sincere gratitude to everyone who has been contributing to the wiki. In particular, thanks for making it one of the best directories of electronics surplus stores on the web!

Photos of The Black Hole

Jeff — Tue, 02 Mar 2010 16:12:36 +0000

Last May, my brother and I went on a week-long roadtrip across the US. Ambling down the highway in a very large moving truck, we travelled from California to Texas by way of Tuscon, Socorro, Albuquerque, Santa Fe, Los Alamos, and quite a few rest stops, gas stations, and fast food restaurants in between.

Intoxicated by the chile verde, we spent considerable time in New Mexico, a state that neither of us had visited before. One of the highlights of our visit to the Land of Enchantment was a side trip to Los Alamos, birthplace of the atomic bomb and home of two major attractions for any electronics geek:

Los Alamos National Labs

Sadly, armed guards prevented us from taking a close look at the Los Alamos National Labs. Actually, the museum is pretty decent, and includes scale models of Fat Man and Little Boy, some exhibits about radioactivity and nuclear weapons, and a short film about the history of the labs.

The Black Hole

The Los Alamos Sales Company, aka The Black Hole, is a surplus store started in 1951 by the late ‘Atomic’ Ed Grothus, a former LANL machinist turned peace activist.

I have never seen a more fascinating collection of electronic test equipment, laboratory glassware, chunks of machined aluminum, LN2 dewars, bell jars, dusty old databooks, and just plain weird stuff. Good news: most of it is for sale, although there are very few price tags around and some items are probably in the “if you have to ask…” category.

A controversial Los Alamos institution, it has even been the subject of a documentary, although I haven’t managed to track down a copy (yet).

Here are some photos to give you a taste of what it’s like to wander around The Black Hole:

A geiger counter near the front door clicks away in response to some radioactive source nearby.

One of several aisles of surplus test equipment. You name it, it’s here.

Mmm… Organic Plutonium!

Anadex CF-300R Timer with gorgeous nixie display.

Racks of vintage test equipment. Scopes, counters, power supplies, etc.

Period datasheet for the Fairchild uA741 operational amplifier.

Pan Am hard hat.

Oscilloscope with permanently attached scope camera. This is the same setup you see in the pictures of atomic bomb test shacks in books such as How To Photograph an Atomic Bomb, by Peter Kuran.

Honestly, the pictures capture only 1% of what you’ll find here – you have to actually visit to appreciate this place. Oh, and budget an hour or two minimum. If you enjoy looking at dual trace oscilloscopes and dusty cold war relics as much as I do, you’ll need an afternoon to really do it justice. If you want to see more, check out my Bradbury Science Museum and The Black Hole albums on Flickr.

By the way, The Black Hole is listed on the Surplus Electronics page of the MightyOhm Wiki. Is there a surplus electronics store in your city? Add it to the wiki!

Announcing the MightyOhm.com Wiki

Jeff — Tue, 02 Feb 2010 17:59:53 +0000

I am pleased to announce that the MightyOhm Wiki is now online and open to the public.

While there isn’t a ton of content yet, my hope is that the wiki will become a useful means to share information and resources relevant to the site. At the moment, there are pages for electronics vendors, hardware/software tools, and PCB manufacturers.

Another page I have been working on for a while is the surplus directory, which lists surplus electronics stores around the country. If you have a favorite surplus goldmine in your area, please create an account and add it to the wiki!

MightyOhm Has a Wiki. Check it out.

Kit Building Party Photos & Video

Jeff — Mon, 02 Nov 2009 19:07:43 +0000

This weekend I hosted a post-Halloween kit building party at MightyOhm HQ.

Nine close friends built Conway’s Game of Life kits from Adafruit Industries. This is my favorite kit for these kinds of workshops because it’s easy for beginners to complete in about 2 hours, and when everyone is done, you can wire all of the kits together to create one large cellular automata display. The last time I helped people build this kit was at a Make:SF workshop at the TechShop in Menlo Park.

Here’s a timelapse video of the afternoon, shot with a Logitech QuickCam Vision Pro webcam on an Eee PC 4G running Booru Webcam 2.0.

The capture interval was 5 seconds. I used Quicktime Pro to stitch the images together at 15fps and iMovie to add titles and music (Turbo Outrun by FRP from remix.kwed.org.)

I wore my Halloween costume for most of the afternoon. What am I? Most people on the streets of San Francisco had no idea…

Safety first!

Stuart was the first to finish his kit:

Soldering the kits together to form the matrix:

Nine happy kit-builders with the 3×3 matrix they created with their finished kits:

And lastly, a video of the 3×3 matrix in action:

Three people had little to no soldering experience at the beginning of the afternoon. Everyone who came went home with a working kit. Success!

Improvements to my microscope setup for SMT work

Jeff — Mon, 26 Oct 2009 19:56:19 +0000

Why do I need a microscope for SMT?

The single biggest challenge to doing “real” SMT work (0805 or smaller components and fine lead pitch ICs) at home is being able to actually see what you are doing. I know that there are many hobbyists (and maybe even some budget-conscious professionals) who will disagree with me, but I wouldn’t dream of working with surface mount components without using a microscope. I’ve tried many alternatives, including a 10X handheld triplet loupe, a magnifier ring light, even a nausea-inducing magnifying visor, and none of these even come close.

In case I haven’t made myself clear: I would rather solder SMT’s with a 150W soldering gun than with anything other than a decent stereo microscope.

In January of this year, I scored a stereo zoom microscope on eBay. While my scope is far from state of the art (it’s a “vintage” American Optical model 569) the optics are fantastic and it quickly became the most prized piece of equipment in my shop. Here’s a photo of the scope shortly after I added it to my lab, for more photos and information about it, see my original post.

For the first few months, I used the scope pretty much as it arrived. One of the first major tasks I used it for was assembling the first batch of AVR HV Rescue Shields, and for this purpose it worked extremely well. However, as time went on, it became clear that I needed to improve my setup in a couple areas:

The magnification range of 7-30X was great for working on a few tightly grouped 0805 or smaller components, but was too high for general PCB work. A typical BGA package was larger than the field of view.
The included incandescent projector-style illuminator (shown piggybacked on the scope in the photo above) could only be placed in a limited set of positions and did not have adjustable focus – it made a nice, bright spot in the center of the image that didn’t fully illuminate the field at low zoom levels. While it is removable from the scope (this provides a workaround for these issues), the included stand took up too much bench space to be practical.

Upgrading the microscope:

The first upgrade I made was to add a secondary objective aka barlow lens to the scope. A secondary objective serves to increase or decrease the total magnification of a microscope, while simultaneously trading off working distance, the distance between the bottom of the microscope and an object in focus on the bench. In my case, I added a 0.5x secondary objective, which gave me half the magnification while increasing my working distance by approximately 2x. While American Optical stopped making accessories for the StereoStar 569 long ago, Reichert, who acquired AO’s microscope line, still sells parts and accesories, including the #575 0.5X secondary objective, shown below.

The secondary objective screws into the existing threads on the bottom of the microscope. Here it is installed on my scope:

Now with the secondary objective installed, I have a zoom range of 3.5-15X and a working distance of 6-8″. If I need higher magnification, I can always remove the lens. Perfect!

The second upgrade I made was to add a fluorescent ring light to the scope. I picked up the cheapest one I could find on eBay. This model is sold by Amscope, outputs 8W, and is available for under $30:

The ring light conveniently attaches to the newly installed secondary objective by tightening three thumbscrews, and provides a decent amount of light that fully illuminates both the object I’m working on as well as the surrounding workbench area, which has been surprisingly helpful. Best of all, the new light stays out of the way and provides more even illumination than the halogen projector that came with the scope.

Here’s a photo of the microscope setup as it looks today:

Conclusion:

While the changes I made are significant improvements over my original setup, I have made a few observations that may lead to even more tweaks and upgrades in the future:

The increase in working distance due to the 0.5x secondary objective is great, but it puts the scope significantly higher above the bench. I didn’t appreciate that this could be an issue until I had to buy a taller lab chair to see through the eyepieces! I’m not sure how to work around this, but it’s good to be aware that more working distance isn’t always a good thing.
The color temperature of the fluorescent ring light is very poor (cool) compared to the halogen illuminator it replaced. This gives everything a slightly depressing blue cast and is far from a true color representation. Most noticeable are tantalum caps, which go from bright orange in color to a sort of slightly orange-ish dark grey under the scope. Yuck!
Ring lights can create pretty nasty glare. This might be a side effect of how I have the ring light mounted or the distance to the bench.
The 8W fluorescent lamp is ok, but more light would be better. Fluorescent ring lights are nice and cheap, but better performance can be achieved with a significantly more expensive fiber optic illuminator. I may look into getting one of these in the future.

Despite these minor issues, I am pretty happy overall with the new setup even after a couple hundred hours of heavy use.

HSC 45th Anniversary Sale this Saturday

Jeff — Wed, 23 Sep 2009 20:26:29 +0000

I just got an e-mail from HSC Electronic Supply announcing their 45th Anniversary Sale (aka Sidewalk Sale), which takes place this Saturday, Sept. 26th. If you are in Silicon Valley this weekend, this is definitely worth checking out. If you want to get an idea of what this event is like, check out my photos from last year’s “Warehouse Clearance Sale.” (It seems like they change the name of this event every year now!)

45th Anniversary Celebration
Local Customer? Come on in and celebrate with us and save
10%-60% on everything in our stores. One day only!
Out of the Area? For our online customers, from September
23rd to 27th, HSC will offer *FREE shipping plus an additional 10%
off any order over $50.00. Just mention “Anniversary Special” in
the shopping cart order notes and we’ll take care of your discount.
The 6,000 items listed online are just a sample of our extensive store inventory.
Don’t see what you need? Please don’t hesitate to call us at 1-800-442-5833.

HSC is having some online specials too, although if you shop online you are missing out on 90% of the fun, such as sifting through crates of miscellaneous electronics parts!

Every project I work on usually involves at least one trip down to the South Bay to visit HSC, and I usually find at least a few interesting odds and ends at their annual clearance sales. And while you’re in the area, I highly recommend a side trip to Weird Stuff Warehouse in Sunnyvale as well.

Tony’s Diamond Chop Saw (Part 3)

Tony — Wed, 19 Aug 2009 20:15:57 +0000

Welcome to Part 3 of the Diamond Chop Saw build. In this installment I’m going to focus on the construction of the mechanical aspects of the saw structure, motor attachment, vacuum chuck, and splash guard. This is a picture-heavy entry…

After thinking for a while about how to build the saw, I decided that it would be best to have the blade move only in the vertical axis, and the workpiece move horizontally in two axes. This led to the overall machine design which consists of a vertical column with pivoting cutting head assembly, and a workpiece holder that has two axes of horizontal motion.

Completed Dicing Saw

I wanted to ensure the motor and blade had a rigid, heavy mounting structure to reduce effects of vibration and flex on cutting performance. I decided to mount the motor using the original mounting flange from the hard drive enclosure since it was nicely machined to match the motor flange. I used a hacksaw to cut out the shape roughly to size, then straightened up the edges and machined a mounting recess on my milling machine. The L-shaped piece of aluminum is 1/2 inch thick which gives lots of weight and provides sufficient thickness for mounting the bearing while preventing motion orthogonal to the bearing axis.

Cutting Head Assembly

Another view of the cutting head assembly. In the upper left hand corner is the pivot bearing. The bearing is held in place with a set screw that goes through the L-shaped aluminum piece. Along the bottom edge of the black hard drive enclosure portion I attached a strip of white LEDs to help light the work area. RTV Siliconeis used to seal the electrical contacts from water that migt not be caught by the splash shield. At the lower left hand corner of the aluminum plate is a rounded off screw. The cutting depth adjustment micrometer pushes against this rounded off screw. Pushing against the aluminum would be less accurate (aluminum would become unevenly worn).

Cutting head assembly (rear view)

At the top of the column on either side is a hole for the screws that hold the pivot bearing (also from a hard drive) in place. Luckily the one I used has 4-40 threaded holes on either side. A screw on each column holds the bearing in place, and then the rest of the column assembly and adjustment plate are attached resulting in a good alignment of the column to the bearing.

Pivot bearing/column mounting detail

Controlling the depth of the cut is critical, as my cuts will be as small as 5 thousandths of an inch deep! I mounted a micrometer head to a plate on the back of the column which controls the height of the cutting head assembly.

Rear view of the column and depth adjustment control

Now for a little detail on the vacuum chuck… The chuck is made from two 1/4 inch plates of aluminum. The top surface has a shallow set of trenches cut to distribute the suction across the bottom surface of the glass plate used for holding parts. The lower plate has a deep trench cut in it to distribute the suction to the three small holes drilled on the top plate. The whole thing is held together with screws and sealed with silicone. I made a set of hose barbs (one is pictured below) so that I can use 1/8 inch vinyl tubing to connect to my vacuum pump. The barbs were made by turning down 10-32 stainless steel screws on my lathe.

Lower half of vacuum chuck with custom-made hose barb

The last major component of the saw is the splash guard. This actually took a fair amount of effort to make, as I broke pieces more than once and had to start over. Essentially it is a two-piece design with a thick piece screwed to the cutting head assembly, and a thinner piece which screws onto the first. I used a heat gun to soften the plastic and carefully mold it to the shape of the face plates. I then glued the curved section and the outer face plate together using epoxy and while not very pretty, it holds together well.

Splash guard on the saw

That pretty much sums up the mechanical aspects of the saw construction. Next week I’ll post the 4th and final installment which will include alignment and attachment of the blade, and actual use of the saw!

Tony’s Diamond Chop Saw (Part 2)

Tony — Fri, 07 Aug 2009 14:30:32 +0000

10, 20, and 5 mil thick alumina substrates with 50 ohm transmission lines

In part 1 I gave an overview of what this project is all about. In this part I will describe the basics of the machine and some of the reasons I made the design choices I did. To start with, I wanted to do this on as small a budget as possible. The main project for which this machine serves ends up being a real money pit, so I have to budget accordingly. Hence the use of hard drive parts and scrap metal. Total spent so far is about $60.

When I first thought about how to cut these little pieces of ceramic, it seemed that there were a few elements that would be tricky on a budget. First thing I did was try and figure out how commercial dicing saws work. Certainly Intel and others have figured out a good way to slice ‘em and dice ‘em a long time ago… And they did.

Tricky thing #1: Holding the substrate while it is being cut.

After a wafer full of chips is finished being made, it is mounted onto a wide stretchy tape, creatively named “dicing tape.” The tape is pulled over a frame and then the wafer placed on top. Next the taped wafer goes into the dicing machine where it is cut by an insanely fast spinning diamond encrusted blade of blingy wafer death.

To keep the wafer from heating up (chips generally don’t like heat) water is sprayed at the cutting surface. This also helps to wash away crud generated by cutting and to prolong blade life. Once the wafer has been diced into individual chips, the tape is exposed to UV light or heat. The adhesive on the tape is made to become less sticky when exposed, and at this point the chips can be easily removed with tweezers, or an automated pick-and-place machine.

My first thought was to try and get some of this tape and use it in the same manner, but for smaller pieces. Then someone at work told me about something far more cool, with a far better name, something called Crystalbond! Crystalbond is essentially a mounting adhesive designed for exactly what I want to do. You simply heat it up, it becomes liquid, place the part in the puddle, and then do nothing until it cools off and then solidly holds your part. I managed to find 5 lifetime’s supply on eBay for dirt cheap, but several other places sell it. Anyway after the parts are cut you wash it away with acetone and you are left with clean diced parts.

Tubes of Crystalbond mounting adhesive

Okay, so the part can be held, but I didn’t want to have to glue a part to my machine every time I wanted to cut something. So instead of gluing the part to the machine I decided to glue the part to small pieces of glass which are a convenient carrier and can be used with my hotplatethat I built for my wire bonder.

Hotplate for thermosonic wedge bonding

So now I’ve got a piece of easy to handle glass, with one or more substrates to dice which has to be mounted to the machine. I could use tape, a temporary adhesive, or clamps, but why? I just put together a digitally controlled vacuum pump for some composites work, so why not make a vacuum chuck? And even better, I mounted it to a precision X-Y dovetail slide that I purchased on eBay for cheap. Now I can easily position the glass, reposition if necessary, and make measured cuts my moving the X-Y stage and measuring at the same time with a runout gauge. This allows me to make cuts that are accurate to 0.001 inches.

X-Y positioner I bought off eBay

A note here regarding XY stages… I chose specifically a dovetail style positioner because unlike the more common linear bearing style slides, a dovetail slide has static loading. The benefit is that there is a much greater resistance to vibration and since I am grinding, I want as solid a mount as possible.

Tricky Thing #2: The Blade

This is really a compound Tricky Thing, a combination of finding the blade, holding it, and spinning it. First a little background on dicing saws and blades…

Wafer dicing used to be done (and still is, especially in research situations) with a diamond scribe, basically a pencil with a diamond at the end. A small scratch is made along the crystal plane of the wafer and then carefully bent until a long, very straight crack is made through the wafer.

The same can be done with alumina substrates, although since it is not a mono-crystalline structure, the crack won’t be as straight or as predictable. Scribe dicing is a relatively labor intensive task and chip manufacturers HATE labor, but even more than that they REALLY HATE any time that an actual person touches a wafer.

Wafer dicing today is usually done with a very thin diamond abrasive blade that grinds away the metal or semiconductor until a cut is made. It is nearly identical to the way you might cut tiles when doing a counter top in your kitchen but on a much smaller scale. When cutting tile, if the blade wobbles a bit or is not centered perfectly, you are not likely to notice. With the alumina substrates I’m working with, the pieces are 20-40 times thinner. This implies that any vibration, wobble, or eccentricity errors can cause problems.

Commercial wafer dicing machines use high speed motors that are carefully balanced and rather than using ball bearings, employ costly air bearings. These are essentially out of reach for hobbyists and really not necessary. What is necessary though is a way to hold and spin the blade accurately. Dicing blades are thin, and the thickest ones I could find on eBay were 300 um wide. At 4.6 inches in diameter, a a very large inner diameter, they are also hard to accurately mount on a typical spindle like that found on a Dremel tool.

Diagram depicting blade mounting: Part A shows the original platter and spacer configuration, Part B shows the modifications I made, Part C shows the blade mounted.

All of these issues led me to use a hard drive motor and platters to spin and hold the blade. Hard drives have very long service lives and need bearings of the highest precision. The mounting of the platters is also done in a precise way, as any imbalance would shorten the bearing lifetime and result in undesirable operation.

To make a long story short, I removed (and reused) the spacer ring between the two platters of a hard drive, and reduced the radius of one platter to 3.5″, the inner diameter of the blade. You can see in the picture that the two platters are stacked and there’s a nice surface for gluing the blade down. Machining the platter down was not easy with my tiny lathe, and it ended up being out of round by perhaps 10 mils. It works to roughly locate the blade, but I will need to tack the blade down, measure, adjust, and finally glue into place. 10 mils out of round is really bad because the thickest substrate I’m working with is 10 mils thick. That means that one part of the blade would never actually do any cutting!

Blade test fitted to the saw.

Tricky Thing #3: Driving the motor

This seemed to be slightly daunting at first. Hard disk motors are typically some kind of brushless motor and require special circuitry to run. I imagined that I would have to build a circuit, or use a motor speed control from a radio controlled plane, etc. It turns out though that the main circuit board in the hard drive I’m using is dumb enough that even though it has had the equivalent of a frontal lobotomy, it just keeps doing it’s job. A couple other hard drives I tore apart did not do this.

Motor Control Box

The box in the picture above shows the hard drive main circuit board and below that, a 12v/5v switching power supply. It’s pretty basic and at the flip of the switch on the front panel, the DC supply is connected to the motor driver and voila, the motor spins up.

Schematic Diagram for the Motor Control Box

Well, that’s about it for this part. In the next part I will discuss the mechanical structure of the saw, fabrication of a few parts, and in the final installment, the use of this machine.

Tony’s Diamond Chop Saw (Part 1)

Tony — Fri, 31 Jul 2009 16:52:55 +0000

This is guest blogger Tony reporting on my latest project, a very small, precise circular chop saw. Why would anyone want to build such a saw you might ask? Well, to make parts for another project of course!

So here’s the background….I’m building a ham radio that operates at 47 GHz. At such a high frequency there are very few components that can be soldered on to circuit boards, let alone components that even come packaged! The easiest way to build a high performance radio at these frequencies is to use MMICs (Monolithic Microwave Integrated Circuits). These are really just fancy, yet fairly simple circuits made from exotic materials, most commonly Gallium Arsenide (GaAs) instead of the usual Silicon used for normal chips. Before MMICs were in widespread use, individual transistors had to be used, requiring delicate and hard to make external matching elements. MMICs are like nice little 50 ohm building blocks. Low Noise Amplifiers (LNAs), mixers, Power Amplifiers (PAs), phase shifters, etc. etc. are all available in this form. Trouble is that you have to connect these pieces up to make a functional radio (or at least the microwave portion of it).

My WestBond wedge bonder

Wire bonding is the usual method for connection and is really just a method of welding a wire (or ribbon) from one chip to the next. It turns out that you actually need space in between the chips, for thermal reasons, RF reasons, and for placing the requisite bypass capacitors. So what goes in between the chips? Well, coax cable is pretty much out, and most common circuit board materials start getting pretty lossy at 10+ GHz, and even the good stuff (PTFE-based usually) starts getting kinda lousy at 40+ GHz. At very high frequencies, materials like ceramics and quartz become worthwhile. In my radio I chose to use pre-made alumina ceramic substrates (tiny circuit boards). These come with a gold layer on the back, and a gold line on top etched to perform as a 50 ohm transmission line (just like coax and just what the MMICs want to see). I bought these with a number of other hams last year in a group buy. They are fairly expensive being that they are 5 and 10 mils thick!

My first test bonds on an alumina ceramic substrate (ugly)

To make the best use of the sections that I bought I decided I needed to cut them to length. Well how do I do that? The thickest pieces are 10 mils thick (a piece of printer paper is 4 mils thick) and they are brittle! Beyond cutting, how do I hold the piece while cutting and when it’s done? The resulting pieces may be just 100 mils long, and 50 mils wide. Obviously a pair of vice-grips simply won’t do.

So my first thought was a Dremel tool and tape. This method could work, but it does not lend itself well to making measured cuts. At 47 GHz, a few hundredths of an inch is a lot! Also, the available diamond blades for dremel tools are fairly wide and I wanted to waste as little of the small substrates as possible. At this point I made a lucky find on eBay.

In the semiconductor industry, one of the last steps of making a chip is called “wafer dicing.” After a wafer full of chips is made, they need to be cut out into individual parts. To do this, wafer dicing machines were developed. These are CNC saws that use a high speed (as high as 60,000 rpm) air bearing spindles with diamond abrasive blades. They can cut lines across large dinner plate sized wafers that are as narrow as only a few tens of microns. Luckily there is enough wafer dicing going on in the world that there is a source of surplus blades on eBay. Not all blades are well suited for all materials, so do some research if you are interested. Disco (a Japanese company) is one of the largest dicing blade manufacturers.

Large (4.6 inch diameter) wafer dicing blade in it's packaging.

While reading the last paragraph you may have spotted a few words indicating unobtanium. Those words are “high speed air bearing spindle.” Well I chose to use a hard drive motor instead, because they have excellent bearings and are readily availble for free. While they don’t move as fast, I don’t care. I have a few short cuts to make, not millions of chips.

So that is an introduction to what I’m doing. For the most part the saw has been built using surplus parts and remnant pieces of metal from my favorite local metal supply house M&K Metals in lovely Gardena, CA. As of this entry, the saw is nearly complete, all that is left is the splash guards. I’ll be posting the build of this project in several parts, so stay tuned.

And a link to my Flickr photo set for this project: Dicing saw

-Tony

Book Review: Hot Air Rises and Heat Sinks, by Tony Kordyban

Jeff — Thu, 14 May 2009 16:47:11 +0000

Everything You Know About Cooling Electronics Is Wrong!

Working as an electrical engineer, I have often been faced with thermal design problems. They are usually in the form of: “Given a maximum system temperature X, ensure that the maximum temperature of all devices in the design does not exceed Y.” Temperature X is usually a customer spec, while temperature Y is almost always driven by MTTF constraints on the semiconductors used in the design. This sounds simple enough until you realize that:

The system temperature is often not clearly defined. Is it the ambient air temperature? The temperature of the printed circuit board the part is mounted on? The temperature of a baseplate (usually a sizable piece of aluminum) that won’t even exist in the finished design?
The MTTF spec is usually based on things you can’t measure directly (at least not easily or accurately), like the junction temperature of a transistor that is on a die you can’t even see, inside a package you don’t have a thermal model for. In addition, MTTF numbers are often wildly inaccurate, don’t account for duty cycle, etc. Yikes.
Chances are, the guy who worked on the part before you hasn’t checked the thermal readings in years, so it’s actually running way over the limits, and now you have to fix it. A small change in the design can drastically affect the numbers

At the end of the day, numbers are scribbled on envelopes or entered into spreadsheets, guesses estimates are made, and everyone resolves to develop a better thermal model next time, which of course never happens.

I stumbled upon this book at the Stanford University Bookstore a few months ago. Given my experience (frustration) with thermal design, I couldn’t help but pick it up and start reading.

It’s a fairly quick read and thoroughly entertaining. Kordyban’s style is very informal. The chapters are in the form of several short stories about fictional characters at a made-up company called TeleLeap. These characters have to solve a series of design problems, which are used as examples to explain several concepts of thermal design. There are no lengthy derivations and the technical discussions are pretty understandable, even to someone who never took thermodynamics in college (like me).

In particular, I found Kordyban’s discussions of the errors that can creep into thermocouple measurements, the difficulty of measuring junction temperature directly, and the problem with pin-fin heatsinks very interesting and educational. I won’t say that I am an expert in thermal design having read this book, but I do have just a little bit more insight into what’s going on (and what to avoid).

Unfortunately, the book is out of print, so you’ll have to find a used copy and pay some big bucks – unless you get lucky like I did and find one that’s still sitting on the shelf. No, you can’t have mine!

Hot Air Rises and Heat Sinks: Everything You Know About Cooling Electronics Is Wrong

The Fat Man and Circuit Girl

Jeff — Thu, 07 May 2009 15:13:14 +0000

The Fat Man and Circuit Girl Cast 9 from Jeri Ellsworth on Vimeo.

I don’t know why it took so long, but recently someone turned me onto The Fat Man and Circuit Girl show, which has been airing on the net for almost six months now. This is definitely the quirkiest and most entertaining electronics themed webcast I have ever seen. The episode above includes an awesome segment about making a floppy drive reverb machine and thoughts on brewing coffee with PID, which reminded me of some other projects I have worked on…

The Fat Man and Circuit Girl are:

George Sanger – (fatman.com)

Musician, artist, composer of music for several video games, most notably Maniac Mansion on the NES and Wing Commander.

Jeri Ellsworth – (blog, twitter, flickr, vimeo, youtube)

Self taught electrical engineer. Designer of the C64 DTV.

I had a chance to meet George and Jeri at NOTACON in Cleveland this month. They are as entertaining in person as they are on video! Jeri told me that she will be at the Maker Faire in San Mateo this year, showing off her Easy-Bake Chip Lab. I am really looking forward to seeing it!

They have a website for the show at fatmanandcircuitgirl.com. You can also follow @fmandcg on twitter.

Who needs television when you can stream a show like this?

Los Angeles Area Surplus Tour

Jeff — Mon, 23 Mar 2009 16:18:09 +0000

Last month I spent a weekend in LA visiting Tony, who is building an awesome wood veneered enclosure for my Wifi Radio project.

While I was there we spent a day checking out various electronics surplus shops in the area, several of which Tony had never visited before.

Here are the highlights of our tour:

All Electronics (Van Nuys, CA)

Most people know (or should know) of All Electronics as a catalog store with a long history in electronics and a decent website. It turns out (I was surprised by this) that you can visit their retail store at 14928 Oxnard Street in Van Nuys.

The store doubles as a makeshift electronics museum, with lots of vintage consumer and industrial equipment strewn around the room.

Stuff to look for: power supplies, handfuls of LEDs, reels of SMT components.

Apex Electronics (Sun Valley, CA)

This is what surplus electronics is all about! Absolute goldmine of bizarre electronics surplus equipment perched on the edge of civilization in Sun Valley. Wire, motors, meters, huge capacitors, electronic components, antennas, hardware, strange military stuff, hydraulics, pneumatics, you name it.

This is probably the best place to find weird surplus electronics junk in all of California, now that most of the Silicon Valley greats are gone or closed to walk-in customers.

We budgeted an hour here and could have spent all day. I would budget at least 2-3 hours or you won’t get to explore the whole store.

Need some decomissioned rocket launchers? You’ll find them here.

More photos of Apex on flickr.

Their website has some awesome Quicktime VR panoramas and extreme wide angle photos, like this one:

Aisle after aisle of surplus equipment @ Apex Electronics

Last year I posted about how surplus electronics junk is getting harder and harder to find in Silicon Valley. Apex Electronics reminds me of RA Enterprises circa 1995 – mountains of electronics equipment waiting for someone to take home and turn into something new.

We didn’t get a chance to visit all of the places we wanted to thanks to LA’s signature traffic jams. Next time I’m back I hope to find some new surplus goldmines and report back.

Suggestions?

Do you know of a place to find cool electronics junk in your area?

I know that the number of stores like Apex and All Electronics are dwindling as eBay and Digi-key take over.

Post in the comments and together we can try to keep these rare stores alive!