Tag Archives: Circuit Cellar

Good electronics videos and articles

My buddy Rob Bowers over at Brocade told me about this video channel for home made (aka Maker) electronics projects. It’s produced by Alan “W2AEW” Wolke. You can see by his nickname and video channel name, he is a Ham radio enthusiast. I never got that bug, my projects were more like a wire wrapped around a nail to make an electromagnet.

The video above is what got my buddy Rob excited. He enthused, “Wow electronics for everybody! There may be hope for me. I watched the one on completing the noise source on the Ham It Up! convertor. He builds it, tests the basics, and the shows a simple use case. I feel .031% less stupid. I wanted to know if I should purchase the noise source parts. ‘Yes’ is the answer, after watching this.”

This is the cool thing about the Maker Movement. Rob is not an engineer. He did software QA in the past and now works at Brocade in the IT department. He is technical, but not formally trained. But the Maker movement is about the fun stuff, and the dreary classrooms and boring lectures are dispensed with in favor of learning with a specific objective in mind. It’s all the fun of engineering without the tedium. We invented computers. They can do the tedium, and the math, for that matter.


Electronics enthusiast Alan Wolke at his bench.

You can see from Alan’s bench the passion he has for radio and electronics in general. Any person with a Metcal soldering iron and a Simpson 260 analog voltmeter is OK by me. The extended CRT (cathode ray tube) housing on that scope makes me think it is the 400MHz Tek 2467B, the fast glitch capture version of the Tektronix 2465B. The CRT is longer to add the plates needed for persistence.

Another cool tip from Rob was about Brocade where he works. He told me the labs have vending machines with cables and mice and other day-to-day engineering essentials. The engineers can just swipe their badge into the vending machine, pick out the cable and be on their way, no requisition forms or hassle. What a class outfit.

The good electronics article tip comes from a fellow eFlea attendee. I saw him at the Roasted Bean in Cupertino and he showed me the latest issue of Nuts and Volts magazine.


Nuts and Volts magazine has a ton of good articles about electronics.

Knowing I worked at Atmel, my pal wanted to point out the above article about Arduino by Joe Pardue. Nuts and Volts is a subscription magazine, so you have pay 27 bucks a year for print and digital, or only 20 bucks a year if you don’t want the print magazine.

Even without subscribing, you can download the code samples for the Arduino 101 article, and if you upgrade to the mysterious un-priced “preferred subscriber network” you get access to all the old issues of Nuts and Volts. This is a great complement to Circuit Cellar magazine, which is also a subscription magazine, but for $250 they can also give you a memory stick with every single article they have ever done. I recommend both these magazines since they are aimed at system design. The trade press, where I have worked, is fine to learn about the latest chip or test method. But Circuit Cellar and Nuts and Volts both show you how to hook up the chips, and do the code and everything else to get a working product. They even touch on 3-D printing and the stuff to put your gizmo in an enclosure. No wonder they can charge for a subscription. All they lack is articles about FCC, CE, and UL approvals, and those might happen one day for all I know.

So keep watching those YouTube videos and reading articles, but more importantly, keep hacking on circuits and code. That is the fun stuff that gives real satisfaction and happiness.

Using Arduino PWM for constant-current drive

The always excellent Circuit Cellar Magazine has a nice article by Ed Nisley. Arduino PWM vs MOSFET Transconductance describes his characterization of Arduino PWM outputs for the constant-current drive of MOSFETs. His application is LED drive, but you could use the knowledge anywhere, including a programmable current sink. Now Circuit Cellar is a paid-subscription magazine, so I can’t link to free article, but maybe their lawyers will let me take a picture of a picture in the print magazine, to which I am a long-time subscriber.


This photo of the board Ed Nisley used to develop his constant-current source tells you it is not some Spice simulation or a theoretical track. This is a sure tip-off that Ed knows what he is writing about.


This scope shot also reassures you that Ed is not venturing forth some opinion on how the hardware and firmware works, it is proof positive he built this stuff and that it really works. I scratched off the readouts to make sure this is fair use and not a violation of Circuit Cellar’s copyrights.

Analog Guru Paul Grohe taught me that you should always look for pictures of real hardware in articles, and that if the curves are ”too pretty” they are probably marketing BS instead of real data. That is the great thing about this article; it’s got both pictures and data that tell you that you can trust the content.

There is another interesting article in the March 2014 Circuit Cellar issue. It’s about an outfit called ImageCraft. They make a C compiler with an IDE (integrated development environment) for Atmel AVR and ARM Cortex-based MCUs. Now I am a fan of Atmel’s free Studio 6 IDE, but feel free to use whatever IDE you prefer to write the code for your projects.

Now I can’t show you these articles on-line, since Circuit Cellar is a subscription print magazine. You have to give them 50 bucks a year to get it. You can get it as a digital pdf if you want to save trees. Its $85 a year for the both print and digital versions. There are large discounts for two- or three-year subscriptions. Best of all, you can give them something like $225 and get every single issue in history on a thumb drive. Then with your combo subscription you can add your monthly pdf to the archive thumb drive, and still have the print edition to impress your friends and boss.

Single wire communication, with power too

I don’t like the term “single-wire communication, since you always need a ground path. My buddy Joe Betts-Lacroix worked on a system at IBM Research where if you shook hands with someone, your PDA (personal digital assistants) would exchange information like your business cards. The “one wire” was your handshake, and the return path was your body’s capacitance to earth.

Most times when you see “one wire communication”, they really mean two wires, they just don’t count the ground return as a wire. No matter, I still think this is a great technology. So I was delighted to see that Dick Cappels had a great article in Circuit Cellar on implementing a one-wire system using an Atmel ATmega8515 microcontroller.


You can tell Dick Cappels is the real deal since he actually builds the one-wire circuit he describes in the article.

This is Dick’s vamp off the Maxim one-wire products that send power and communicate to a device over a single wire (not counting that return path). This was dreamed up by Dallas Semiconductor, before Maxim bought them in 2001. What I like about Dick’s solution, besides his using an Atmel MCU, is that for a couple of cheap parts, you can do one-wire communications with any peripheral made by anyone, as long as you go slow enough. He calls it analog communication, which I also love.

This does not send a lot of power along with the bits; in fact, you don’t have to send any power if you don’t want to, but you should be able to scale things as needed. It is a subject near to my heart, since I dreamed up a system a few years ago to send power to a motorcycle headlight and communicate to the switches and gauges all over one wire. I will check out Cappel’s design, since we can all learn from each other.

Now a word about Circuit Cellar. You can read that blog post I linked to above, but the article itself is behind a paywall. I can attest, Circuit Cellar is worth every dime if you are a system engineer that is interest in hardware, firmware, and even mechanical hacks. It’s a little on the hobby side, but nobody will do your engineering job for you for 30 or 40 bucks a year.

I mentioned a Circuit Cellar article on a homebuilt DNA sequencer a while back—and I say it again, subscribe and pay the bucks for this great magazine. I thing they have a money-back deal, and best of all, for 230 bucks or so you can get all the old issues on a memory stick, and then add your pdf issues to that stick. Do be aware that it costs extra to get both print and pdf versions.

ATmega32 in your home-built DNA sequencer

The May 2013 issue of Circuit Cellar magazine has a great article by Fergus Dixon, who uses an Atmel ATmega32 microcontroller to operate a DNA sequencer.

One of the dozen ways to sequence DNA is to apply a reagent to the DNA sample. If the reagent reacts with the base pair on the end of the DNA strand it splits the pair and emits a tiny burst of light. If it is a double pair the burst of light is twice as strong. Then you just work your way up the DNA strand “zipper,” breaking the pairs and recording which of the 4 pairs you just broke. Now you understand why it took years to sequence even a short DNA strand.


Here is a control board from a DNA sequencer designed by Fergus Dixon

Fergus had the usual engineering fun you might expect when doing something this cool. The flat-black box he housed the light sensor in had a tiny hole. Light variance in the room showed up as noise. He had to figure out a method to drive stepper motors so they were smooth and got to 3000 RPM. He designed reagent solenoid injector drivers that worked off of 100V pulses, while also fiddling with the SPI ports. My consultant buddy John Haggis swears that any serial interface will take up 6-person months of labor.

I used to laugh at that – but I now think he is right. You have to get the hardware working, develop protocols, test for exception conditions – yeah, I can see six months just getting two devices to talk to each other.

You can see that Circuit Cellar has some great articles. The same May 2013 issue has an article on a wi-fi connected energy monitor, a serial port to SPI programmer, a G-code CNC router, a MIDI communication device, and a reprint of a radiation monitor – like a Geiger counter.

Now I can’t show you these articles on-line, since Circuit Cellar is a print magazine. And you have to give them 50 bucks a year to get it. You can get it as a digital pdf if you want to save trees. Its $85 a year for the both print and digital versions. There are large discounts for two- or three-year subscriptions. Best of all, you can give them something like $225 and get every single issue in history on a thumb drive. Then with your combo subscription you can add your monthly pdf to the archive thumb drive, and still have the print edition to impress your friends and boss.