MightyOhm

Rigol DS1052E 50MHz to 100MHz scope hack

Jeff — Thu, 11 Mar 2010 18:49:10 +0000

Hack a Day posted yesterday that a guy named Ross turned his 50MHz Rigol DS1052E into a 100MHz capable instrument by removing part of a lowpass filter on the analog inputs.

I think it remains to be seen whether there are any other mods required to make this work like a real DS1102E (ie. does the 1052E firmware limit the minimum horizontal timescale?) but this is hardware hacking at its finest!

Read more about it on the EEVblog forums.

Agilent firmware update confirms Rigol connection

Tim Williams: The Circuit Designer’s Companion

Jeff — Wed, 10 Mar 2010 18:20:12 +0000

I recently picked up a copy of Tim Williams’ Circuit Designer’s Companion after I noticed it on my Amazon recommendations list (which seems to know my tastes a little too well these days.)

This is a fun and useful book. The emphasis is on practical information that is useful to working engineers, not PhD students. This means that there are a lot fewer equations in this book than The Art of Electronics and it’s a lot less intimidating for someone without a degree in Electrical Engineering. The book’s roughly 400 pages include topics such grounding and shielding sensitive circuits, some basic tips for routing PCBs, why it’s usually better to buy a switching power supply than build your own, some comparisons of batteries, and how to pick a fuse. (Sadly, the latest microcontrollers and Lithium battery technologies are missing – not surprising, since the 2nd edition was released in 2005. Time for an update?)

I like Williams’ writing style, and usually pick this book up first to see if he has a quick solution to the problem at hand before diving into one of my more dense engineering texts. While this book isn’t a replacement for my other (heavier) reference books, it’s a welcome addition to my desk. I keep it within easy reach.

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!

Quick look at the Blinken Button

Jeff — Tue, 23 Feb 2010 16:31:24 +0000

Here’s a quick look at the new Blinken Button kit from Interactive Matter.

If you want to try your hand at surface mount soldering, this is a fun project that can be completed in a couple hours with a decent soldering iron and a pair of tweezers. The instructions aren’t perfect (I had to short across the PCB pads for D1 and D2 to get my programmer to talk to the AVR, and at the moment you have to install Eclipse to compile the hex file) but I am confident that these minor issues will be fixed shortly!

Datasheet Hell

Jeff — Fri, 12 Feb 2010 15:46:37 +0000

I would love to know what this datasheet says because I’d like to use this part in a project.

Details such as “the part will self ignite if you hook it up thusly” would be particularly helpful.

Can anyone read Russian (Cyrillic)?

Update:

Thanks to everyone who stepped up to translate the datasheet! You guys are awesome!

Here is a photo of the tube that I am pretty sure goes with the datasheet above. It’s a CI-3BG Glass Geiger Müller Tube from Electronics Goldmine.

Electronics Goldmine’s description mentions that this tube is intended to detect gamma rays. Based on the translations, this is true, but the tube appears to be sensitive to beta radiation as well. This is one of the things I was hoping to learn from the datasheet, in addition to the driver requirements and any hints about it’s original application.

The unique part about this tube (to me) is that the envelope is made of glass, and the “active area” (or whatever it is called) is fairly small – this is perhaps consistent with the intended application in very high radiation environments. If anyone knows anything else about these tubes and their differences compared to more “traditional” metal-can Geiger tubes, please leave a comment!

No idea what I am talking about? Wikipedia to the rescue!

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.

Los Angeles Area Surplus Tour

Samsung WEP470 Bluetooth Headset Pics

Jeff — Thu, 28 Jan 2010 23:33:09 +0000

Bill Owens recently shot a couple photos of the Samsung WEP470 Bluetooth headset, aka the $3 Woot Headset.

This headset looks like a great platform for hacking, but to my knowledge noone has turned one into a Retro Wireless Handset yet…

There is some more info about the WEP470 in the forums.

Gary’s Wifi Radio Project

Jeff — Tue, 19 Jan 2010 16:01:41 +0000

Gary Dion (N4TXI) created a Wifi Radio to match his entertainment center. His project is inspired by my original Wifi Radio project and shares several of the same parts (such as the Asus WL-520gU wireless router) and design philosophy.

Interesting features of Gary’s version of the radio:

Very cool 4 line VFD display allows more information to be shown at once (and it’s blue!)
AVR sends actual shell commands to the router, which allows the serial console to remain enabled for debugging/other purposes – brilliant!
Nice custom PCB for the ATmega8 microcontroller
Rotary encoder and significantly more advanced control menus
IR remote control support!

More details, photos, and source code are available on Gary’s site.

Thanks to the Make: blog for bringing this project to my attention!

Debugging (David Agans)

Jeff — Mon, 11 Jan 2010 16:02:58 +0000

I recently saw David Agans’ book Debugging mentioned in one of the many trade journals I receive (I can’t remember which one). After seeing how much praise it received on amazon.com, I decided to pick up a copy.

Debugging really spoke to me because a large portion of my career has been devoted to finding and fixing hardware bugs. I finished it in just two or three evenings (it’s a quick, fun and engaging read). The examples are particularly interesting and relevant to me because many involve issues with embedded systems. Admittedly, perhaps most fascinating is the one about a living room lamp that turned on anytime the author vacuumed the room.

I highly recommend this book to anyone who regularly troubleshoots issues with any kind of system, software or hardware, mechanical or electrical. This includes engineers of all discplines, circuit designers, computer programmers, helpdesk operators, web developers, auto mechanics, etc.

David’s nine rules of debugging are (with my notes):

Understand the system – Knowing how your circuit, code, or widget is supposed to work will help you fix it. Read the manual!
Make it fail – Knowing how to reproduce the failure is critical to being able to fix it. Also, stimulate the failure, don’t simulate it.
Quit thinking and look – Don’t jump to conclusions and just fix what you think might be the problem. This wastes time when you inevitably guess wrong. Keep an open mind as to what the failure mechanisms could be.
Divide and conquer -Eliminate what is definitely not part of the problem and focus on what’s left.
Change one thing at a time – If you change ten things at once, how will you know which one actually solved the problem?
Keep an audit trail – Being able to reproduce the fix is crucial. Even if you don’t fix the problem, you might discover a pattern or something you overlooked by looking at your notes.
Check the plug – When all else fails, check the obvious stuff that you probably should have looked at first.
Get a fresh view – Someone else may have more experience with the problem than you do or might see the one thing you’re missing.
If you didn’t fix it, it ain’t fixed. - Don’t stop when the problem just disappears. It will surely come back later at the most inconvenient time possible. We’ve all been bitten by this one before. Never again!

There’s even a free poster available on the book’s website to help you remember these rules during your next debugging crisis.

Tony’s Diamond Chop Saw (Part 4)

Tony — Mon, 04 Jan 2010 16:00:23 +0000

Finally, I bring you the conclusion of my Diamond Chop Saw series!

In this part I’ll cover a few remaining issues, but mostly I’ll report on my use of the machine in the construction of my 47 GHz radio, for which this project was intended. If you’re not already familiar with this project, you might want to go back and start by reading Part 1.

Attaching/Aligning the Blade

Attachment of the blade to the hard disk platters (see part 2) sets the basic accuracy of the tool. If the blade is out of plane the cut will be wider than the blade. If the blade is off center, portions of the blade will wear faster. Achieving perfection is virtually impossible, but I managed to get a ‘good enough’ result.

My method was to lay the ring blade down onto the larger platter and use tape to temporarily hold the blade in place while I manually spun it around to check for centering.

Method for centering the blade

A little fiddling and re-alignment will get things pretty close. After the centering is good, the next step is to glue the blade into place. I used tiny drops of Zap-a-Gap around the inner edge of the ring and held the two together firmly as the glue set.

After gluding the blade, spots of glue are visible on the top surface

The result is not perfect, but cuts I have done seem to be sufficiently narrow.

The Cutting Setup

The picture below shows the setup for making cuts. The large silver box in the background is the vacuum pump, the green vise in front is holding a digital indicator (for making precisely measured cuts) and the blue airbrush is ready for spraying water onto the cutting surface.

Dicing saw setup

The parts to be cut are mounted on glass slides using Crystalbond adhesive, a thermoplastic mounting polymer.

Test substrates about to be cut

Using the Chop Saw

Below are some pictures of cuts made with the saw.

A partial cut through one of the substrates

Several diced pieces.

Microscope view of a part diced into three pieces

From the photos above it is clear that the saw is working reasonably well. The cuts are straight, the pieces have no obvious large chunks missing, and the gold metallization shows minimal signs of peeling. I have made many cuts using this saw including angled cuts. I have also used the saw to carefully strip off the backside metallization. This will come in handy when I am making diveboard-style waveguide transitions. I have also used the X/Y table to feed the piece along the blade, allowing me to make much longer cuts than in “chop” mode. These came out very nicely as well.

The accuracy of the saw is reasonably good. Using a dial or digital indicator, cuts can easily be made with 0.001 inch accuracy, which is sufficient for circuits working through 50 GHz at least.

One issue that was of concern initially was whether a hard drive motor actually had enough power to do the job. It turns out the motor works fine as long as the cuts are made slowly. Fast cuts are not advisable anyway, as the part is more likely to fly off into oblivion. Some of the substrates I cut had fairly thick metal backing and required slower cuts.

Future Improvements

Every project ends up with room for improvement. With this project a few things come to mind including a precision machined spindle with a better mounting mechanism. This would require a much larger lathe than what I own, and some careful though into balancing. Another improvement would be a self-contained coolant sprayer and vacuum pump for the chuck. Setting up the dicing saw currently requires a vacuum pump, an air compressor, and so on. Another nice feature would be a microscopic camera to observe the cutting in action. And finally a CNC retrofit would be nice. All of these upgrades would be handy, but as it is, the saw is immensely flexible and precise. I’m still on the first blade which is showing no signs of wear.

Conclusion

It has been a lot of fun putting together this series of articles and even more fun putting together and using this saw. So if you are planning on putting together a saw like this, happy cutting! If you are just planning on building something with a hard drive motor, they are really handy for certain applications where high precision, high RPMs, and cheapness are required.

$3 Bluetooth Headset on Woot

Jeff — Sun, 03 Jan 2010 09:53:23 +0000

Woot is selling a Samsung Bluetooth headset for $17.99 + $5 S/H – $20 MIR = $3 after rebate.

For that price this headset could be a great candidate to use for a DIY Retro Bluetooth Handset.

The catch is that I can’t guarantee this headset is actually hackable until someone buys one and reports back here.

Who will be the first?

Retro Wireless Handset featured as Make: Weekend Project

Jeff — Fri, 01 Jan 2010 19:44:11 +0000

In this week’s Make: Weekend Project, KipKay shows us how to turn a Bluetooth headset into a retro-styled wireless handset.

This project is based on the ‘Retro Wireless Handset’ article I wrote for Make: magazine volume 20.

KipKay also posted a pdf version of the article so now you can read about this project even if you’re not a Make: subscriber.

Enjoy!

2009 in Review

Jeff — Thu, 31 Dec 2009 14:44:34 +0000

Wow, 2010 came a lot quicker than I expected! With one day to spare, here’s a brief look back at some of the highlights of 2009 here at mightyohm.com.

DIY PID-Controlled Soldering Hotplate:

I needed a hotplate for surface mount soldering, so I built one from scratch using a milled block of aluminum, a 500W cartridge heater, and a surplus PID controller. Some of my favorite DIY projects have been building my own tools, and this one is a great example.

The AVR HV Rescue Shield:

This year saw the release of my first electronics kit, the AVR HV Rescue Shield. Designed in response to my own experience accidentally setting the RSTDISBL fuse on an AVR microcontroller, the AVR HV Rescue Shield has helped many microcontroller enthusiasts around the world rescue their otherwise crippled, stuck, or deaf AVR’s.

My Wifi Radio Project:

After planning out the project and completing a good chunk of the software in 2008, most of the construction of my Wifi Radio project occurred in the early part of 2009. I put the finishing touches on the radio for the 2009 Bay Area Maker Faire. Around the same time the project also made it onto Engadget (and a bunch of other blogs as well). This project continues to be one of the most popular projects on the site and has inspired several other projects based on the Asus WL-520gU wireless router, including an extension to the Adafruit Industries Tweet-a-Watt.

This brings me to:

Notacon 6:

In April I flew out to Cleveland and gave a talk about Hacking the Asus WL-520gU Wireless Router at Notacon 6. The con was a huge amount of fun but reminded me just how much work it is to give a talk. I met lots of cool people there, including George Sanger and Jeri Ellsworth, aka The Fatman and Circuit Girl.

By the way, the submission deadline for talks at Notacon 7 closes on January 31st!

DIY TiVo IR Blaster:

My DIY TiVo IR Blaster was a simple hack constructed in an hour entirely out of parts I already had in the lab. The best part is that eight months later, it’s still working flawlessly. Like any good hack, this one is cheap, simple, and just works.

Harrison’s Box:

This project, codenamed “Harrison’s Box“, was a collaboration with my wife Kylie and my father-in-law Bill to build an “electronic box” to give to my nephew Harrison’s on his first birthday. We added as many switches, knobs, and lights as we could. Harrison loved it!

Retro Wireless Handset / Make Magazine:

I originally posted about my Bluetooth Handset Hack back in November of 2008, but it took exactly one year for the article I wrote about it to finally be published in Make: magazine volume 20. I just learned that my Retro Wireless Handset will be featured in an upcoming episode of the Make: Weekend Projects podcast. Cool!

Those are some of the highlights of 2009. I hope to bring more cool projects, hacks, and kits to you in 2010!

Lastly, Happy New Year and a sincere thanks to everyone who has been reading the blog, leaving comments, buying kits, or supporting the site in some way over the past year!

Happy Holidays…

Jeff — Sun, 20 Dec 2009 18:12:35 +0000

Hello everyone! Happy Holidays from mightyohm.com!

Extended traveling, 8-bit music festivals, and holiday planning have kept me away from a keyboard recently, but I hope to post more soon.

Stay tuned…

The Crucible’s annual Holiday Gifty Art Sale this weekend

Jeff — Wed, 09 Dec 2009 20:56:55 +0000

The Crucible’s Holiday Gifty Art Sale 2009 is this weekend, December 12th and 13th, from 10AM to 4PM at their shop in West Oakland.

Admission is free!