MightyOhm

Online store (temporarily) closed, kits still available through distributors

Jeff — Wed, 16 May 2012 17:02:58 +0000

A quick update: As of last Saturday night I am no longer taking orders for kits.

The easiest way to do this was to remove all inventory from Paypal’s online ordering system, so if you try to place an order you will get the dreaded “out of stock” error message.

Fear not!

Geiger Counter kits are still available through my distributors (click each logo to visit the corresponding product page):

Adafruit Industries

Maker Shed

HV Rescue Shields are available from:

Solarbotics

A huge thanks to everyone who took advantage of last week’s special pricing on Geiger Counter kits. Enjoy your new kit! (And if you need help getting it working, I’ll still be monitoring the support forums, so ask your questions there.)

Thanks again!

-Jeff

See you this weekend at the Maker Faire Bay Area!

Jeff — Mon, 14 May 2012 14:17:05 +0000

The Maker Faire Bay Area is this weekend (May 19 & 20th) at the San Mateo County Event Center.

I’ll be in the Maker Shed selling Geiger Counter kits. I’ll be doing a demo on Saturday at 6PM in the Shed and will also be giving a presentation about finding radioactivity in everyday objects on the Make: Demo stage in Expo Hall on Sunday at 2PM.

Stop by and say hello!

Just a few Geiger Counter kits left, online store closes tomorrow at midnight

Jeff — Fri, 11 May 2012 17:44:11 +0000

This week only, $99.95 gets you a Geiger Counter kit with sensitive SBM-20 Geiger tube and a clear acrylic case.

Thanks to everyone who has been taking advantage of the reduced pricing on Geiger Counter kits this week, there are just a handful left in stock.

If you’ve been holding out on placing an order, now might be a good time. There’s a fair chance that I’ll run out of kits before I close the online store at midnight tomorrow (CDT).

PS: There are still some HV Rescue Shields in stock as well.

Update: I have been asked if I am closing up shop permanently – hopefully not! I plan to reopen the online store after I move to Seattle, but my new day job might slow down the process a bit. I’ll post updates as I get settled.

Austin Mini Maker Faire this weekend at Pine Street Station

Jeff — Wed, 09 May 2012 15:19:30 +0000

The Austin Mini Maker Faire is this weekend!

This is the first Make: sponsored event we’ve had since the “big” Faire in 2008. It’s being held at the Pine Street Station in East Austin (5th and Waller).

I’ll be there checking out all of the cool exhibits, including the soldering workshops being run by my friends at the ATX Hackerspace.

Click the poster below for more information, or visit austinmakerfaire.com.

See you there!

Geiger Counter Kits on sale this week, online store closing May 12th

Jeff — Mon, 07 May 2012 23:06:16 +0000

This week only, Geiger Counter kits are on sale!

For a limited time, $99.95 gets you a Geiger Counter Kit and a stylish clear acrylic case.

Also, my online store will be closing this weekend (May 12th) and will reopen after I unpack in Seattle next month.

Working at Valve

Jeff — Fri, 20 Apr 2012 22:23:46 +0000

Yes, the things you have heard are true. After four glorious years of freelancing and working on fun open source hardware projects, I am going full-time again.

In June, I will be joining the hardware team at Valve.

Yes, Jeri works there. No, she is not my boss (or anyone else’s, more on that later).

On my last visit to Valve, I got a copy of the brand new Handbook for New Employees. This handbook outlines what it’s like to work at Valve.

If you read the handbook, you will discover that working at Valve is quite a bit different than working at other software or hardware companies.

Perhaps most significantly, Valve is a completely flat organization – there are no managers. (And by flat I don’t mean simple, or boring, because it is certainly neither of these things.)

No one, not even Gabe, can tell you what to do or what projects to work on.

So how does anything get done? Simple:

Interested in working at Valve? The handbook also talks a bit about the sorts of things that Valve looks for in the hiring process. I found this diagram particularly interesting:

Valve looks for people who are experts in their field but also generalists. (Jack of all trades, master of one?) This applies across all disciplines.

(Does this sound like you? If you are interested in working on hardware in an amazing work environment, surrounded by other super-talented people, I highly recommend that you contact Valve.)

The handbook contains lots of other good information for new and prospective employees. Unfortunately, it’s not available for download (yet), so you’ll have to come visit and beg for/borrow/steal a copy. (In the mean time, there are a few more scans here.)

As for me, I need to start packing. Wish me luck.

Update: LambdaGeneration just posted a link to the complete handbook.

Soldering is Easy Comic Book turns 1

Jeff — Wed, 11 Apr 2012 14:09:44 +0000

Today marks one year since Mitch Altman, Andie Nordgren and I released our Soldering is Easy comic book.

Since then it has been translated into 15 other languages (not including Morse Code) and has been downloaded more times than we can count (40,000 times in the first week alone).

I would like to extend our sincere thanks to all of the translators and to everyone else who has helped spread our comic book around the world. I’ve seen it at hacker conferences and Maker Faires, referenced in university electronics courses, and posted at hackerspaces in very far away places.

Thanks for making our comic book such a huge success, we couldn’t have done it without you!

Geiger Bot on the iPad

Jeff — Thu, 05 Apr 2012 19:04:03 +0000

Last week I went to my local Apple store and came home with a shiny new iPad.

Why? So I could play with Geiger Bot for the iPad, of course!*

Fortunately that’s not the background level in my lab, but a measurement of a Fiestaware plate I have in my collection of “slightly radioactive stuff“.

* Not really, but it is pretty cool.

How to use Geiger Bot with the MightyOhm Geiger Counter

Jeff — Fri, 09 Mar 2012 20:46:15 +0000

Geiger Bot is an iOS application that allows you use your iPhone or iPad as a sophisticated display for an ordinary Geiger counter. It works with most Geiger counters that make an audible “click” for each event or count that is detected.

Here’s how to get your MightyOhm Geiger Counter working with Geiger Bot. These instructions were tested with an iPhone 4, but should work with other iOS devices (iPads and other versions of the iPhone).

Connecting your MightyOhm Geiger Counter to an iOS device

The documentation that comes with Geiger Bot claims that you can collect data by holding your Geiger counter up to the microphone of your iOS device. I didn’t find this to be the case – the number of counts registered was inconsistent and strongly affected by background noise. A direct connection is definitely preferable, so we need devise a way to connect our Geiger counter to our iOS device.

The easiest way to do this is by using the microphone input. Apple uses a 3.5mm 4-way headset connector that is somewhat unusual (you’re not going to find it at Radio Shack). The easiest way to get your hands on the proper connector is to cannibalize a wired headset. Bonus: You get a short length of nice flexible cable for free!

While you could use a genuine Apple headset for this, the quality of the headset isn’t important (since we’re just going to cut it apart anyway). Use the cheapest headset you can find. This one, by Miztech was $3.99 at my local Fry’s Electronics:

The sales rep actually tried to steer me away from buying such an awful headset (I tested it, the audio quality is horrible), but quickly disappeared after I tried to explain what I planned to do with it.

The pinout of the headset connector is well-documented online, but here’s a quick diagram:

We don’t care about the left and right audio outputs. What we’re interested in is the microphone input and the “common” pin, which we will tie to ground.

Cut the headset wire just before it reaches the strain relief for the microphone and strip away about an inch of the insulation to expose the wires inside. Use your soldering iron to tin each of the wires. It takes a few seconds, but the enamel insulation will dissolve into the solder, exposing the copper wires underneath:

Use your DMM or other continuity tester to determine which wire color corresponds to which pin on the headset connector.

The wire colors vary for different headsets. (Apple uses a completely different scheme for their headsets, and combines the microphone wires in a single twisted pair.) In my case, two samples of the same headset had a different pin assignment (no wonder they didn’t work so well!)

The MightyOhm Geiger Counter outputs a short (100 microsecond) pulse on pin 2 of header J6 (marked PULSE) every time an event is detected. This pulse, which is active high, swings all the way from ground to the full battery voltage of the kit, typically around 3V.

The iPhone microphone input expects a much smaller signal, less than 100mV. (I measured that the microphone input starts clipping around 40mVpp @ 1kHz!)

Before we connect the Geiger kit to the microphone input, we need to reduce pulse signal amplitude to levels that are compatible with our iOS device. This simple circuit will do the trick:

C1 is a ceramic (nonpolarized) capacitor and R1 & R2 are common 1/8W carbon resistors.

I built the circuit on a small piece of protoboard and parts I had in the lab.

…and used hot glue to protect the delicate headset wires. I made sure to provide ample strain relief for the headset cable. When plugged into the Geiger kit, the resulting adapter looks sort of like a diving board hanging off the side:

It’s not pretty, but it works!

Configuring Geiger Bot

If you haven’t already, open the Apple App Store and install the Geiger Bot application.

Launch Geiger Bot and you should see the home screen:

Click on the small gear icon to open the settings menu:

Select Geiger Counter

Select Custom GM Tube…

You can leave the Conversion Factor and Offset alone for now. Select I/O Settings…

I experienced lots of missed counts with Auto Adjust enabled, so against the author’s instructions I suggest turning it OFF. RMS Window and Delay Windows didn’t seem to have much of an effect, but I recommend starting with RMS Window = 1 and Delay Windows = 30. The Volume Threshold is the most critical adjustment, and I recommend setting this to 20000.

Scroll down to see more settings:

The other critical setting is Ultrafast Rates, this needs to be turned ON to get reliable counts with my kit (I think this is because the pulse length is short compared to other kits). Leave the rest of the settings at the default values.

Return to the settings page and click Done to return to the Geiger Bot application.

Testing

Make sure your Geiger counter is connected to your iOS device. Turn the Geiger counter on. Within a few seconds, you should start seeing counts register on the display:

If you touch the right arrow under the graph a couple times, you can see a display of the pulse signal as intepreted by Geiger Bot. Each vertical peak is a detection event, blue pulses are registered as counts, while black pulses are ignored:

The red line is the volume threshold, and this should be comfortably below the minimum level of the peaks, or you will occasionally miss pulses. If your display looks similar to the one shown, Geiger Bot is working.

That’s it! For more information about Geiger Bot and how to use its many features, consult the Geiger Bot documentation.

Hopefully this helps everyone who has been asking for a way to use Geiger Bot with the MightyOhm Geiger Counter kit!

Enjoy!

Comments or questions? Post in the support forum!

An Analog Life: My pilgrimage to the workbench of analog guru Jim Williams

Jeff — Fri, 24 Feb 2012 18:03:49 +0000

Last week, while visiting the San Francisco Bay Area, I had a chance to visit the Computer History Museum.

Surprisingly, I didn’t go there to see their impressive collection of vintage computers, although I highly recommend checking out the PDP-1, Babbage Engine, and Revolution, a tour of the first 2000 years of computing.

Instead, I went there to check out An Analog Life, a temporary exhibit at the museum. There, I got to see first-hand the famously cluttered workbench of the late analog guru Jim Williams.

Jim’s workbench holds an impressive collection of vintage test equipment, but Jim particularly loved old Tek scopes, and his 547 is on display:

There’s also a Tek 454 and a 576(?) curve tracer on the bench:

Jim worked on making efficient laptop backlight power supplies for many years, and there are a lot of artifacts from this long term project on his desk, including God’s Own Backlite Current Calibrator:

I’m not sure what’s going on with his desk phone, but it appears to be the recipient of some sort of hack:

There is so much stuff on the bench that it takes a while just to take it all in. Yes, there is a soldering iron somewhere in this photo:

Jim’s workbench (more photos) is impressive, and reason enough to visit the museum. But the freshly-remodeled museum is really breathtaking, and the new exhibits are excellent. Plan to spend a day here, or you’ll discover (as I did) that 3 or 4 hours isn’t enough time to see everything.

The Computer History Museum is located in Mountain View, California. An Analog Life runs through April 15th.

For more on Jim Williams, I recommend checking out Reading Jim Williams, a blog about Jim’s famously well-written (and sometimes humorous) app notes.