Simple Circuits: Turn a Tube Radio Into an MP3 Amp

Want to give your MP3 player vintage tube sound? You can with the proper circuits, an antique radio, and a little know-how. In addition to generating amazing sound, the design will be an eye catcher in your home or office.

Here I present excerpts from Bill Reeve’s article, “Repurposing Antique Radios as Tube Amplifiers,” in which he provides vintage radio resources, simple circuit diagrams, and essential part info. He also covers the topics of external audio mixing and audio switching. The article appeared in the May 2012 edition of audioXpress magazine.

Manufactured from the 1930s through the 1960s, vacuum tube radios often contain high-quality audio amplifiers at the end of their RF signal chain. You can repurpose these radios into vintage, low-power tube amplifiers—without marring them in any way or detracting from their original charm and functionality as working analog radios.

Wood-cased radios have especially good sound quality, and the battery compartments in antique “portable” radios (like the Philco 48-360 or the Zenith Transoceanics) provide perfect locations for additional circuitry. When restored properly, large furniture-style radios that were built for “high fidelity” (like the late 1930s and early 1940s Philco console radios) can fill a room with rich beautiful sound.

Simple Circuits

The simple circuits described in this article perform two functions. They mix an external line-level stereo signal (typically from an MP3 player or computer) and reference it to the radio’s circuit. They also use the radio’s on/off knob to switch this external signal to the radio’s audio amplifier.

There is not one circuit that will work for every antique radio. (Original schematics for antique tube radios are available on the web www.justradios.com). But the circuits described here can be adapted to any radio topology. All the parts can be ordered from an electronics supplier like Digi-Key, and the circuit can be soldered on a prototyping printed circuit board (such as RadioShack P/N 276-168B).

External audio mixing

Figure 1 and Figure 2 show some examples of circuit schematics that mix the line-level stereo audio signals together (almost all tube radios are monophonic), while providing galvanic isolation from high voltages within the radio. Figure 1 shows an inexpensive solution suitable for most table-top radios.

Figure 1: An inexpensive circuit for mixing an MP3 player’s stereo audio signals safely into an antique radio. None of the component values are critical. (Source: B. Reeve, AX 5/12)

These radios have relatively small speakers that are unable to reproduce deep bass, so an inexpensive audio transformer (available from on-line distributors) does the job. I picked up a bucket of Tamura TY-300PR transformers for $0.50 each at an electronics surplus store, and similar transformers are commercially available. Alternatively, the Hammond 560G shown in Figure 2 is an expensive, highquality audio transformer suitable to high-fidelity radios (like the furniture-sized Philco consoles). A less expensive (and fine-sounding) alternative is the Hammond 148A.

Figure 2: A high-fidelity circuit for mixing external stereo audio signals safely into an antique radio. (Source: B. Reeve, AX 5/12)

I use Belden 9154 twisted, shielded audio cable for wiring internal to the radio, but twisted, 24-gauge wire will work well. An 8′ long audio cable with a 3.5-mm stereo jack on each end can be cut in half to make input cables for two radios, or you can use the cord from trashed ear-buds. You can route the audio cable out the back of the chassis. Photo 1 is a photograph of a 1948 Philco portable tube radio restored and used as an MP3 player amplifier.

Photo 1: A 1948 Philco portable tube radio restored and repurposed as an MP3 amplifier. (Source: B. Reeve, AX 5/12)

Audio switching using the radio’s on/off knob

After creating the mixed, radio-referenced signal, the next step is to build a circuit that switches the voltage driving the radio’s audio amplifier between its own internal broadcast and the external audio signal.

Figure 3 illustrates this audio routing control using the radio’s existing front panel power knob. Turn the radio on, and it behaves like the old analog radio it was designed to be (after the tubes warm up). However, if you turn the radio off, then on again within a few of seconds, the external audio signal is routed to the radio’s tube amplifier and speaker.

The circuit shown in Figure 3 uses a transformer to create the low voltage used by the switching circuit. There are many alternative power transformers available, and many methods of creating a transformerless power supply. Use your favorite….

The next photos (see Photo 2a and Photo 2b) show our additional circuit mounted in the lower (battery) compartment of a Zenith Transoceanic AM/shortwave receiver. Note the new high-voltage (B+) capacitors (part of the radio’s restoration) attached to a transformer housing with blue tie wraps.

Photo 2a: The inside view of a Zenith Transoceanic AM/shortwave radio restored and augmented as an MP3 audio amplifier. b: This is an outside view of the repurposed Zenith Transoceanic AM/shortwave radio. (Source: B. Reeve, AX 5/12)

The added circuit board that performs the audio re-routing is mounting to a 0.125″ maple plywood base, using screws countersunk from underneath. The plywood is securely screwed to the inside base of the radio housing. Rubber grommets are added wherever cables pass through the radio’s steel frame.—Bill Reeve

Click here to view the entire article. The article is password protected. To access it, “ax” and the author’s last name (no spaces).

CircuitCellar.com and audioXpress are Elektor International Media publications.   

A Workspace Built for Precision Design

Brad Boegler is a do-it-yourselfer’s DIYer. His West Bloomfield, MI-based workspace is something to admire. It features a sturdy 8’ × 5’ workbench, a well-built machining bench, and dozens of handy tools that enable him to work on projects ranging from constructing a temperature-monitoring network to milling custom heatsinks. Simply put, it’s an appealing space for any innovator interested in DIY electronics and machining projects.

Photo 1: One of Boegler's Altera CPLD breakout boards is on the bench. He said he was "experimenting with some video generators in VHDL" when he took this picture. (Source: B. Boegler)

As I reviewed Boegler’s space, the same word kept popping into my mind: precision. Why? Let’s see.

Building a bench (or benches) for a workspace like Boegler’s takes a lot of precision measuring, cutting, fitting, and constructing. Check out the workbench in Photo 1. That’s no “Ikea hack.” The 8’ × 5’ bench fits a dual monitor setup, plenty of test/measurement equipment, a solder station, and more.

Boegler—who works as Linux sysadmin—described some of the equipment on this bench via email:

The left side of the bench is mostly RF equipment: there are two HP RF frequency generators, a VNA, and spectrum analyzer. The analog scope is a Tek 2246 and is one of my favorite scopes. Next to that is an HP 16500B logic analysis system and then a HP 54112D digital scope … The bench was custom made. I was not able to find any benches to my liking so I ended up building my own. It is 8′ wide by 5′ deep and constructed out of mostly 4×4s. It weighs a ton, but it has to be sturdy as a lot of this equipment is very heavy. I like very deep benches as I can push the equipment back far enough on it and still provide enough working space.

And don’t forget the power!

Those are various adjustable voltage current limiting power supplies, when working on projects needing various voltages you can never have too many supplies.

I’m sure everyone agrees that access to power supplies is key.

Photo 2: Boegler's workspace for machining (Source: B. Boegler)

On a separate bench (Photo 2) are Boegler’s milling machine and drill press, which are two tools intended for precision designing and machining. Boegler wrote:

The drill press is used almost daily, one of the best tools ever. I use the milling machine for custom shielded aluminum cases for RF boards, making special sized heatsinks, and it comes in handy for any special brackets I can make to hold boards or components.

I’m sure you’d agree that machining board cases and heatsinks requires a bit of exactitude.

Much like the bench in Photo 1, building the actual machine bench required precise measurements and cuts. Just look at its clean edges and sturdy frame. And don’t you like the shelf underneath? It’s a simple yet effective place for stowing frequently used tools.

On the topic of storage, check out Boegler’s wheeled shelf system. I like it and will consider something similar for my garage. (We all take wheels for granted until we’re in a pinch and need to move a heavy object. For instance, try moving a wheel-less six-shelf system full of parts in order to track down a screw that fell on the floor. Actually, don’t try that. It’s an accident waiting to happen.)

A wheeled shelf system for microcontrollers, op-amps, and parts of all sorts (Source: B. Boegler)

Lastly, check out the neatly labeled parts boxes. I see labels such as “Microcontrollers/DSP,” “Op-Amps,” “Serial Cables,” and more. Nice!

Share your space! Circuit Cellar is interested in finding as many workspaces as possible and sharing them with the world. Click here to submit photos and information about your workspace. Write “workspace” in the subject line of the email, and include info such as where you’re located (city, country), the projects you build in your space, your tech interests, your occupation, and more. If you have an interesting space, we might feature it on CircuitCellar.com!

Issue 263: Privately Funded Engineering

The public vs. private funding debate endures in the United States and Europe. Everything from energy generation (e.g., oil) to social welfare programs are debated daily by government committees, discussed in corporate board rooms, and argued over at lunch tables from Los Angeles to Brussels and beyond.

One particularly interesting discussion pertains to the role of the public and private sectors in space flight and exploration, which comprises fields such as aerospace design, embedded electronics, and robotics. In Circuit Cellar June 2012, Steve Ciarcia weighs in on this debate and makes a thought-provoking argument for the benefits of privately funded engineering endeavors. In “Google LUNAR X Prize” he writes:

This is certainly an exciting time to be an engineer. We have seen the success NASA has had with robotic exploration, especially on nearby planets such as Mars. Contrary to everything coming from NASA in the future, however, thanks to the advances in robotics and launch vehicles, “space” will soon become the province of private enterprise and not just government. Very soon, commercial space flight will become a reality.

The Google Lunar X PRIZE provides a focal point for these efforts. Google is offering a $20 million prize to the first team to complete a robotic mission to the moon. The basic goal is to put a lander on the surface of the moon, have it travel at least 500 m once it’s there, and send back high-definition pictures and video of what it finds. There’s a $5 million second prize, and also $5 million in bonus prizes for completing additional tasks such as landing near the site of a previous NASA mission, discovering water ice, traveling more than 5,000 m while on the surface, or surviving the 328-hour lunar night.

When the Lunar X PRIZE registration closed in December 2010, a global assortment of 33 separate teams had registered to compete. Seven of those teams have subsequently dropped out, but there are still 26 active teams, including 11 from the U.S. The first launch is expected sometime in 2013, and there’s plenty of time before the competition ends December 31, 2015. Some teams are even planning multiple launches to improve their chances of winning.

It’s interesting to browse through the team information and see the vast diversity in the approaches they’re taking. This is the part that is most exciting from an engineering point of view. Some teams are building their own launch systems, while others are planning to contract with existing government or commercial services, such as SpaceX. There’s a huge amount of variety among the landers, too: some will roll, some will walk, and some will fly across the moon in order to cover the required distance. Each one takes a different approach to dealing with the difficult terrain on the moon, and issues such as the raw temperature extremes between blazing sunlight and black space.

This sort of diversity is a powerful driver for future development. Each approach will have its strengths and weaknesses, and there will certainly be some spectacular failures. Subsequent missions will draw on the successful parts of each prior one. Contrast this to the approach NASA has tended to take of putting all its effort into a single design that had to succeed.

It’s also interesting to consider the economics of this sort of competition. The prize doesn’t really approach the full investment required to succeed. Indeed, Google is quite up front about the fact that it probably only covers about 40%, based on other recent high-tech competitions such as the Defense Advanced Research Projects Agency’s DARPA Grand Challenge and the Ansari X PRIZE. This means the teams need to raise most of their money in the private sector, which keeps them focused on technologies that are commercially viable.

I have long been a fan of “hard” science fiction, as typified by writers such as Larry Niven, Arthur C. Clarke, and Michael Crichton. To me, hard science fiction means you posit a minimal set of necessary technologies, such as faster than light (FTL) space travel or self-aware computers/robots, and then explore the implications of that universe without introducing new “magic” whenever your story gets stuck. In particular, Larry Niven’s “Known Space” universe—particularly in the near future—includes extensive exploration of the solar system by private entrepreneurs. With the type of competition fostered by the Google Lunar X PRIZE, I see those days as being just around the corner.

The competition among these teams, and the commercial companies that arise from them, will be good for society as a whole. For one thing, we’ll finally see the true cost of getting to space, as opposed to the massive amounts of money we’ve been pouring into NASA to achieve its goals. As a public agency, NASA has many operational constraints, and as a result, it tends to be ultra-conservative in terms of risk taking. Policies that dictate incorporating backups for the backups certainly makes a space mission more expensive than the alternative.

Despite these remarks, however, I don’t mean to sound overly negative about NASA at all. It has had many spectacular successes, starting with the Mercury, Gemini, and Apollo manned space programs, as well as robotic exploration of the solar system with the likes of Pioneer and Voyager, and more recently with the remarkable longevity of the Mars rovers, Spirit and Opportunity. There have been many beneficial spin-offs of the space program and we have all benefited in some way. We wouldn’t be where we are today without the U.S. space program. But the future is yet to be written. There are striking differences between a publicly run space program and the emerging free-market privately funded endeavors. We would do well to recognize the opportunities and the potential benefits.

Circuit Cellar 263 (June 2012) is now available on newsstands.

Issue 263: H2M & M2M Communication

Before I introduce this issue, I’d like to bring your attention to our recently redesigned website, CircuitCellar.com. It enables engineers and programmers around the world to communicate and share ideas via project articles, videos, and social media. The site’s features range from project posts (how-to articles, videos, and photos) to daily updates about products and industry news. We also run short write-ups on actual circuit cellars and workbenches in the well-received “Workspaces” section of the site. I encourage you to submit photos and info about your workspaces. Share your space with the design community!

Now let’s focus on this issue, which has articles on both human-to-machine (H2M) and machine-to-machine (M2M) communication. Topics as diverse as smart switch management and human motion-sensing systems are covered.

Kevin Gorga kicks off the issue with his “AC Tester” project (p. 14). It is an isolated variable voltage power source that includes an electronic circuit breaker for testing and debugging equipment. An mbed controller displays voltage and current, and it controls the breaker’s trip point and response time.

Circuit Cellar published 15 of Aubrey Kagan’s articles from 2000 to 2010. In an interview on page 24, Aubrey shares some of his engineering experiences from designing controllers for mines in Africa to helping create specs for the remote control arm on the International Space Station.

On page 28, Fergus Dixon presents a ’Net-connected controller for up to 50 smart switches for lighting systems. The controller’s RTC pulses a 24-V AC line once or twice to turn off the smart switches at the end of the day.

Final PCB with a surface-mount Microchip Technology ENC28J60 Ethernet chip (Source: F. Dixon, CC263)

Turn to page 36 if you’re interested in computer vision technology. Miguel Sánchez introduces depth camera technology, and describes how he used Microsoft’s Kinect in an interactive art project.

On page 44, columnist Bob Japenga starts an articles series on the subject of concurrency in embedded systems. In this article, he defines concurrency and covers some concurrency-related pitfalls.

Last month columnist George Novacek examined the topic of product testing and simulation. In this issue, he tackles a different yet equally important topic: diode ORing (p. 48).

On page 52, columnist Ed Nisley carefully explains MOSFET channel resistance. He describes power MOSFET operation and explores the challenges of using a MOSFET’s drain-to-source resistance as a current-sensing resistor.

A serious RF designer should have a sound understanding of frequency mixers. On page 58, columnist Robert Lacoste summarizes the basics of RF mixers and presents real-life applications.

A simple single-diode unbalanced mixer and its simulation done with Labcenter's Proteus. The RF and LO frequencies are 340 MHz and 300 MHz respectively. You can see on the output spectrum that these two frequencies are still visible, but as well as the difference 40 MHz and sum 640 MHz, among others. (Source: R. Lacoste, CC263)

Jeff Bachiochi wraps up the issue with an article about a DIY, MCU-based blood pressure cuff project (p. 68). He converted a manual blood pressure cuff into an automatic cuff by adding an air pump, a solenoid release valve, and a pressure sensor.

Circuit Cellar Issue 263 (June 2012) is now available on newsstands.

Electronics Engineering Crossword (Issue 263)

Across

1.     SPARKGAP—A space in an otherwise closed electric circuit [two words]

3.     FUZZYLOGIC—Began in 1965 with Lotfi Zadeh’s proposal of a certain type of set theory [two words]

6.     NULLTEST—Cancels a device’s signal input by negative feedback from its output [two words]

7.     COULOMB—One of these is equal to 6.28 x 1018 electrons

10.   EDDYCURRENT—A.k.a. Foucault currents [two words]

11.   KIRCHHOFF—Created a law of thermochemistry

13.   ANDGATE—Relies on truth and logic  [two words]

16.   HOLONYAK—Invented the LED while working at General Electric in the 1960s

17.   SOLIDSTATERELAY—Doesn’t rely on movement or contact to switch electric circuits [three words]

20.   ACCIRCUIT—A circuit with a current that goes one way and then another [two words]

Down

2.     ANNEAL—Run hot and cold

4.     OPTOISOLATOR—Changes electrical signals to light and back into electrical signals

5.     CHECKBIT—Adds a bit to make things even or odd [two words]

8.     MICROFARAD—1,000,000 pF

9.     THEVENIN—French engineer (1857–1926); augmented Ohm’s law

12.   KELVINSCALE—Temperature scale where 0° = absolute zero [two words]

14.   PHOTODIODE—Turns light into current or voltage

15.   ACORNTUBE—A small tube used at very high frequencies [two words]

18.   ERG—Causes 1 cm of movement

19.   ASCII—A character-encoding system used to represent text

 

A Workspace Where Meccano Meets Arduino

Peeking into someone’s workspace gives you a glimpse of their interests, personality, and aspirations. Thus, in the same way no two personalities are exactly same, no two workspaces are identical. Some workspaces are retreat-like locations where designers spend their precious “alone time”; other spaces are 24/7 where innovators work, play, eat, and even sleep. Some spaces are intended for leisurely designing, learning, programming, and tinkering. Other spaces are high-pressure work zones where electronics innovators endeavor around the clock to create the systems and programs that pay their bills. And so it’s due to the personal nature of each workspace that we’re grateful to the generous innovators who’ve pulled back the curtains to give us a look.

Today let’s check out a space that’s intended more for innovation and learning than building the next money-making embedded system.

Ralph Laughton’s multifunctional London-based workspace was designed for model-making and Meccano-building. It wasn’t intended to be an electrical engineering workspace.

But Circuit Cellar and Elektor members shouldn’t overlook a space simply because it isn’t full of MCUs, soldering irons, PCBs, and EE test equipment. You can learn a lot by studying someone’s work area: innovative storage systems, novel workbench designs, handy power supply solutions, equipment customization, and more.

Laughton's bench in London

Laughton wrote the following with his submission:

Please find attached a photograph of my modest workspace here in my workshop in London, England. My space has to be shared with other activities such as model making as in this picture. Component storage and larger equipment is stored to one side of the bench, keeping the main area clear. The shelves across the window are mounted on adjustable brackets. Not only does this give flexibility, but it enables easy access to the window and blind for cleaning and maintenance.

On his blog he writes:

My workshop has to accommodate woodworking, model making, photography as well as anything else that needs fixing, modifying or investigating.

When comes to investigating, Laughton has begun learning about Arduino. In late April he posted the following about his early experiences with it:

I am now at the stage where I can make it do what it is supposed to do and I have even written and modified my own lump of code. This may not seem like much to some of you reading this but for me this is a big leap into the world of digital electronics and microprocessors—something I didn’t think I would ever entertain. Mind you, what do I know? I used to think digital photography would never catch on.

So, with Arduino and the recent purchase of a scope (see his May 2 post), Laughton is positioning himself to take on more electronics projects in his multifuctional workspace

We can’t wait to see what sorts of Arduino-controlled Meccano projects he creates.

Do you want to share photos of your personal electronics workspace, hackspace, or “circuit cellar”? Do you have an article or tutorial you’d Circuit Cellar to consider for publication? Click here to submit your proposal or write-up and photos. Write “Submission” or “Proposal” in the subject line of your email.

MCU-Based “PHOTO-PAL” Camera Controller

A while back, I designed a camera and flash control device that will be the subject of a future Circuit Cellar magazine article.  This device, which I affectionately call Photo-Pal, allows me to use sound (or a contact closure) to trigger a high-speed electronic flash after a user specified delay. The device consists of a microphone amplifier, a Microchip Technology PIC16F873A microcontroller, a 2 × 16 character LCD, and six pushbuttons for the user interface. Delay from sound trigger input to flash trigger output can be adjusted from 1 to 59,999 ms.

The Photo-Pal design (Source: R. Lord)

The high-speed photos are taken in complete darkness with the flash as the only light source for the photo.  The Photo-Pal device also controls the camera shutter. Once the room lights have been turned off, an “arm” push button input causes Photo-Pal to remotely press the camera shutter button, causing the camera shutter to open. The sound trigger input is also enabled. The triggering sound then starts a delay countdown, which then triggers the flash output. Once the flash has fired, the Photo-Pal then releases the camera shutter. 

For the last several months, I have been experimenting with using Photo-Pal to freeze the action of a light bulb being shattered by a hammer, water droplets rebounding from a surface, and eggs being shattered by a pellet from a BB gun.

The BB gun timing setup (Source: R. Lord)

 

For the photos using the BB gun to smash an egg, I needed to make a cradle to hold the gun so that each shot would be aimed at the same location. I also needed to establish how long it took for the pellet to reach the egg.

An egg hit by a BB (Source: R. Lord)

To make the measurement, I bolted three sheets of plastic together and drilled a large “target” hole. I then sandwiched two sheets of aluminum foil between the three sheets of plastic so that the two foil layers were separated. The microphone for the Photo-Pal was attached to the cradle so that it would be triggered when the BB gun was fired. My oscilloscope was triggered by the Photo-Pal flash output with delay set at 0, and the interval was measured between the time of the trigger output and the moment when the two sheets of aluminum foil were shorted together by the pellet passing through them. With the target set 4 feet from the muzzle of the BB gun, this time interval was measured to be 25 ms. For the egg photographs, I added another 20 ms to the delay so that the flash would catch the egg in mid-burst, after it had started to fly apart. The 45-ms delay was then programmed into Photo-Pal for the photos.

Egg smashed and sound-triggered flash (Source: R. Lord)

 

The Photo-Pal device has several other modes of operation where it can produce a burst of flash outputs for a stroboscopic effect, or can activate the camera’s shutter from sound or at periodic intervals for time lapse photographs. As you can see, the Photo-Pal device is a useful photography tool that also can be a lot of fun to play with.

Richard Lord holds a B.S. in Electrical Engineering and an M.S. in Biomedical Engineering. During his career, he has designed digital electronics for an aerospace company and several telecommunication test equipment manufacturers. Working as a consultant in the 1980s, Richard designed several medical pulmonary test instruments and the electronics for an autonomous underwater robot. His 2011 article “Panning Control: A Digital Indexing Panoramic Tripod Head” appeared in Circuit Cellar 248.

Editor’s note: Do you have an article or tutorial you’d Circuit Cellar to consider for publication? Do you want to share photos of your personal electronics workspace, hackspace, or “circuit cellar”? Click here to submit your proposal. Write “Submission” or “Proposal” in the subject line of your email.

EE’s Two-Bench Workspace in Silicon Valley

I met Vincent Himpe—a Senior Staff Engineer at STMicroelectronics—a few years ago at the Emebdded Systems Conference in San Jose, CA. It took all of about 5 minutes to learn that he was an engineer with a lot on his mind. Himpe described his work on hard disk drives, sketched a few circuits on a piece of paper, and even mentioned a few ideas for books. (Yes, that’s books—plural.) Where does such a productive engineer get so many ideas and all that energy? I wondered after we parted. I didn’t get to ask him before the conference ended.

Fortunately, Himpe recently contacted me, so I took the opportunity to get more insight into the life of such a multitalented engineer. I sent him a few questions via email, and he kindly replied. We have some insight into where he does a lot of creating, problem solving, programming, and writing.

When Himpe isn’t working on advanced controller devices for hard disk drives at STMicro, he’s writing books (check out Mastering the I2C Bus, Elektor 2011), tackling personal design projects, and repairing surplus electronic electronic equipment in two-bench workspace in San Jose.

My short interview with Himpe appears after the following two photos of his San Jose-based workspace.

Vincent Himpe’s workbench for hardware development

Himpe’s workbench for programming

C. J.: What are you working these days?

VINCENT: I make the reference designs and the development system for a hard disk mechatronic interface chip. This chip spins the 3 phase motor, does the head positioning including velocity control for the seek algorithms, shock sensing (to park the heads when freefall or shock is detected), provides power to all other parts (it’s got 4 switching regulators onboard). In case of unexpected power loss, we protect the data by retracting the heads. We recycle the mechanical energy in the spinning platters by using the motor as generator. This gives us a few seconds of power where we can gracefully shutdown the drive, preventing disasters.

C. J.: What sorts of projects do you work on at these two workstations? Work-related projects? Personal projects?

VINCENT: Personal projects. I have a number of books published through Elektor. Some of the hardware for those was developed there.

C. J.: Can you tell us a bit about the equipment at your hardware workstation? What do you use most frequently?

VINCENT: This is almost all salvaged equipment that was half functioning or broken. Some machines were repaired by combining two broken ones. I scout local surplus stores and eBay for damaged equipment. And once in a while you get lucky. There was a local company moving to a new building. They had ceased hardware development a couple of years ago and only do IP blocks now. They had a “yard sale.” That’s where I picked up my logic analyzer and my favorite scope: an Agilent mso7104: 4 analog and 16 digital channels 1GHz bandwidth with deep memory and all the protocols enabled.

C. J.: It looks like you’re working on something at the hardware bench. On the shelf is some equipment with red wires.

VINCENT: Those are three bench power supplies e3410 from Agilent. Next to it are three 34401 multimeters, also Agilent. I’m a bit of an Agilent fan. The fact that you can easily get full-service manuals that include schematics, calibration and troubleshooting procedures makes it ideal to fix these machines. That’s not the case with many other brands. Plus, they are built to last.

C. J.: What’s the piece of equipment directly under the magnifier/lamp?

VINCENT: Looks like a roll of desoldering wick. I was working on the ringlight. You can see a circular PCB just above it. Thirty-six white LEDs driven by a current-controlled boost pump with PWM. The halogen light bulbs in my Mantis burn out too easily. So I will replace them with this ringlight.

C. J.: How many solder stations do you have at your hardware station?

VINCENT: About seven. I have a Microtouch for precision work, SMD tweezers to remove passives, a hot air pencil, two WSP80s with different tips (so I don’t have to switch tip continuously while working), and a regular desoldering station with a vacuum pump. These are all surplus and/or repaired machines.

C. J.: What is board you’re working with at your software station?

VINCENT: That is a controller board for a UV exposure unit to make PCBs. It’s got an ATmega328 and LCD display. The board does double duty as pizza oven reflow controller. Just install two thermocouple interface chips and change software.

CircuitCellar.com is an Elektor International Media (EIM) publication. EIM published Himpe’s book, Mastering the I2C Bus.

Propeller Games (P1): Hi Lo

Welcome to the Propeller Games! In a few installments, I’ll present several gaming projects that use the Parallax Propeller chip. The Propeller is perfect for gaming with its multiple CPU cores to handle simultaneous gaming activities and its on-board video generation circuitry.

My first game project is the classic “higher/lower” game, where the computer thinks of a number between 0 and 99 and you guess it. You have probably seen this played as the “Clock Game” on The Price is Right TV show, though some contestants struggle with a basic binary search algorithm. (You can watch videos of the game at YouTube.com.)

This entire project is built on a solderless breadboard. If you are new to the Propeller, this is the perfect project to get acquainted with the hardware and programming. If you are a Propeller guru, you will enjoy the nostalgia of gaming on LEDs and push buttons. Grab your breadboard and follow along.

Parts

What you’ll need:

  • Breadboard and wire
  • 9-VDC wall transformer
  • Parallax PropStick USB
  • Two-digit 7-segment LED display
  • Five SPST pushbuttons
  • Audio speaker
  • Sixteen 200-Ω resistors
  • Five 10-kΩ resistors

The board and basic parts

The Parallax Propeller chip requires a few external components. You need a 3.3-VDC power regulator, a crystal, and a USB-to-serial converter. You also need a serial EEPROM if you want the Propeller to run your program at power up. You can buy all these separately and wire them up on the breadboard. Or you can save time and space with the Parallax PropStick USB. It combines all these external parts on the same footprint as the 40-pin Propeller chip.

I bought the LED display for this project from Mouser Electronics (part number 630-HDSP-521E). The large red segments are common anode (common ground). You supply positive voltage from a propeller port pin through a 220-Ω resistor to light the segments.

I bought the push buttons from Pololu Robotics & Electronics (part number 1400). They are specially designed for mounting on a breadboard. One side of each switch is connected to 3.3 V and the other is connected to a propeller port pin and pulled to ground with a 10-kΩ resistor.

I bought the speaker from Digi-Key (part number 668-1140-ND). The negative terminal of the speaker hooks to the breadboard’s ground. The positive terminal hooks directly to a Propeller port pin.

A speaker, one LED segment, and one switch wired to the Propeller

I placed four of the switches on the corners of the display. These switches are used as up/down inputs for each digit allowing the player to select a number from 00 to 99. The fifth button to the right of the display is the “Enter” button.

The photo above shows the speaker, one LED segment, and one switch wired to the Propeller. I tested the hardware and software incrementally as I hooked it up instead of trying to debug the final system as a whole.

The Parallax Propeller Tool is the free graphical Integrated Development Environment (IDE) you use to develop code for the Propeller. The code editor colors and highlights your work making it easy to see functions and keywords. It also manages indentation. The SPIN programming language uses indentation to identify code blocks much as Python does.

Basic hardware test

The code above is my basic hardware test. The CON (constants) section at the top configures the clock speed of the chip: 5 MHz × 16 = 80 MHz. The OBJ (object) section pulls in the serial terminal driver library. This library object allows you to use the USB cable for both programming and an input/output terminal. The one second pause on line 12 gives you time to switch from the IDE program to the terminal program on your PC once the code is downloaded. The Propeller tool download includes the parallax serial terminal for your PC.

Line 10 sets general I/O pin 0 (P0) as an output (they are inputs by default). Line 17 reads the switch connected to P11 and turns the LED segment on or off accordingly. Line 18 prints the state of the input pins to the PC terminal in an infinite loop.

Parallax serial terminal

It took me a while to warm up to the SPIN programming language. It is syntactically very different from C and its derivatives. But conceptually it is familiar: you break your software up into functions and local/global variables. In the end the simplicity of the syntax and the friendliness of the IDE won me over!

I really like the “Propeller font” used in the Propeller Tool IDE. It includes special symbols you can use to draw circuits and timing diagrams in your code comments. For instance:

Check out the font

Now to wire up the rest of the LEDs and switches. I thought about wiring the left digit to the first port byte and the right digit to the second port byte so that the segments are laid out the same way in each byte. This would make the software easier to write. But the pins for the segments on the display are kind of scattered around at random. The wiring is easier and neater if you wire the segments from the bottom of the display to the bottom of the propeller and from the top of the display to the top of the propeller. You can make up for the scattered pattern with software.

Two tips: Wire the segments from the bottom of the display to the bottom of the Propeller. Wire from the top of the display to the top of the Propeller.

Hi/Lo breadboard layout

That’s it for this installment. Now I’ll clean up all the little wire stripping sprinkles I left around my workbench. In Part 2 of this series, I’ll switch modes from hardware to software and write the Hi/Lo game. Hopefully you are following along. Until next time, may the COGs be ever in your favor.

Chris Cantrell earned an MSEE from the University of Alabama. He writes Java and Flex for Emerson Network Power in Huntsville, Alabama. Circuit Cellar published 10 of his articles between 2002 and 2012: Issue 145, Issue 152, Issue 161, Issue 184, Issue 187, Issue 193, Issue 205, Issue 209, Issue 139, and Issue 260.

One Electronics Workspace Among Nuremberg’s Thousands

Living in and around the international technology hub of Nuremberg, Germary, are tens of thousands of professional electrical engineers, tech-focused academics, and electronics DIYers. According to the city’s website, the IT sector—comprising radio technologies, embedded systems, and software development—has more than 100,000 employees working in more than 7,000 companies.

Heiner Tucher's bright, sufficiently powered electronics workspace

Within this burgeoning city and metro area are innovative circuit cellars, hack spaces, and workspaces of all sorts. Let’s take a look Heiner Tucher’s space.

With a general interest in electronics, Tucher built the space to serve as his “personal hobby room.” He works with older parts, and builds some of them himself. The tube-based generator is still full functional, he said.

If you look closely, you’ll see Tucher smartly equipped his workbench with a few essentials that every serious electronics designer should consider for his or her space:

  • Sufficient power: It’s no secret that easily accessible, wall-mounted power strips make designers’ lives much easier. Tucher has a great power supply setup.
  • Smart Storage: The process of designing and programming an electronic system comes with plenty of obstacles and bugs. So why create more headaches for yourself by cluttering your space or mixing random parts in unlabelled boxes and drawers? A storage system doesn’t have to be expensive or elaborate. Tucher made good use of what look like basic cabinets with decent depth. Nice and simple, yet extremely useful.
  • Proper lighting: Check out the overhead lamp Tucher placed suffificently above the main work bench. Notice how you don’t see any shadows from his various pieces of equipment. That’s essential when working with small components.

Do you want to share images of your workspace, hackspace, or “circuit cellar” with the world? Click here to email us your images and workspace info.

A Workspace for Radio & Metrology Projects

Ralph Berres, a television technician in Germany, created an exemplary design space in his house for working on projects relating to his two main technical interests: amateur radio and metrology (the science of measurement). He even builds his own measurement equipment for his bench.

Ralph Berres built this workspace for his radio and metrology projects

“I am a licensed radio amateur with the call sign DF6WU… My hobby is high-frequency and low-frequency metrology,” Berres wrote in his submission.

Amateur radio is popular among Circuit Cellar readers. Countless electrical engineers and technical DIYers I’ve met or worked with during the past few years are amateur radio operators. Some got involved in radio during childhood. Others obtained radio licenses more recently. For instance, Rebecca Yang of Tymkrs.com chronicled the process in late 2011. Check it out: http://youtu.be/9HfmyiHTWZI and http://tymkrs.tumblr.com/.

Do you want to share images of your workspace, hackspace, or “circuit cellar” with the world? Click here to email us your images and workspace info.

 

Elektor Weekly Wrap-Up: Projects Update & LED Book/Kit

Yet again, last week was hectic yet productive for my Elektor colleagues overseas: articles were edited, design projects were undertaken, and much more.  Here’s the inside scoop on two important items.

Progress  at “Elektor Projects”

The “Elektor Projects” website is officially live, and members have begun sharing their electronics experiences and discussing projects.

Check out some of the current projects members can join:

  • Pico C-Plus and Pico C-Super
  • MYC, a universal system to control devices and programs
  • Sub low pass filter
  • Wheelie 2
  • USB record digitizer with RIAA correction
  • Analog Theremin

Go to www.elektor-projects.com to find out more.

LED Book & Kit Promo

Elektor announced a nice offer for members interested in Willem van Dreumel’s book Fun with LEDs. For a limited time, Elektor members get 15% discount and free shipping and handling. Here’s the info about the book straight from Elektor:

LEDs are found everywhere these days. These colorful lights seem to offer so many you may wonder where to begin using them. This booklet presents more than twenty exciting projects covering LEDs, aimed at young & old. From an Air Writer, a Party Light, Running Lights, a LED Fader right up to a Christmas Tree.

Use this book to replicate various projects and then put them into practice. To give you a head start each project is supported by a brief explanation, schematics and photos. In addition, the free support page on the Elektor website has a few inspiring video links available that elaborate on the projects.

A couple of projects employ the popular Arduino microcontroller board that’s graced by a galaxy of open source applications.

An optional 60-piece starter kitis also available with the book.

Starter kit

The kit includes:

  • 1 pc. breadboard w. 270 contacts
  • 1m hookup wire
  • 1 pc. 9V battery clip
  • 27 pcs. carbon film resistor (27E, 56E, 82E, 150E, 270E, 330E, 390E, 8x 470E, 560E, 1K, 6x 2K2, 10K, 3M9, 4M7, 5M6)
  • 4 pcs. ceramic capacitors (10nF; 5mm pitch)
  • 5 pcs. BS170
  • 1 pc. LM555CN (NE555CN)
  • 1 pc. C4017 (HEF4017)
  • 3 pcs. trimpot, horizontal (1K, 10K, 100K, + 3 wheels), pitch 10mm/12.5mm, with spindle
  • 1 pc. RGB LED (4-pin)
  • 1 pc. UV LED, 5mm
  • 1 pc. LED, 5mm, Rainbow (Colour-Change)
  • 5 pcs. LED, diffuse, red, 5mm
  • 5 pcs. LED, diffuse, yellow, 5mm
  • 5 pcs. LED diffuse, green, 5mm
  • 3 pcs. LED, bright blue, 5mm
  • 3 pcs. LED, bright white, 5mm
  • 2 pcs. 1N4148 diode
  • 3 pcs. 10uF electrolytic (10uF/25V), pitch 2.54mm
  • 3 pcs. 220uF electrolytic (220uF/25V), pitch 5mm
  • 1 pc. 74HC14
  • 1 pc. LM324
  • 1 pc. CD4093 (HEF4093)
  • 3 pcs. BC547B

You can use the kit build and test circuits on a breadboard without having to get involved with soldering.

CircuitCellar.com is an Elektor International Media publication.

 

Project Spotlight: Electronics + Wood Fab Speakers

MIT graduate student David Mellis is interested in how designers are combining high-tech parts like microcontrollers with low-tech materials in clever ways. Yesterday, I pointed everyone to Mellis’s inspiring 3-D Printed Mouse project. Now let’s look at another creative design—Fab Speakers.

Whether you’re a microcontroller fanatic, professional engineer, audiophile, musician, or all of the aforementioned, this open-source Fab Speakers project will surely inspire you to customize your own. I’d love to see how others tackle a similar DIY project!

Fab Speakers (Source: D. Mellis)

Mellis writes:

These portable speakers are made from laser-cut wood, fabric, veneer, and electronics. They are powered by three AAA batteries and compatible with any standard audio jack (e.g. on an iPhone, iPod, or laptop).

The speakers are an experiment in open-source hardware applied to consumer electronics. By making their original design files freely available online, in a way that’s easy for others to modify, I hope to encourage people to make and modify them. In particular, I’d love to see changes or additions that I didn’t think about and to have those changes shared publicly for others to use or continue to modify. The speakers have been designed to be relatively simple and cheap in the hopes of facilitating their production by others …

Use 6mm (1/4″) plywood. For the veneer, 1 9/16″ edging backed with an iron-on adhesive is ideal (like this one from Rockler), but anything should work if you cut it to that width. Pick whatever fabric you like. For the electronic components, see the bill-of-materials above. You’ll also need two-conductor speaker wire, available at Radio Shack… There’s also a wall-mounted, oval-shaped variation on the design. It uses the same circuit board, but combines both speakers into a single unit that can hang on a nail or screw in the wall. You’ll want to replace the batteries with a 5V power supply (included in the bill of materials); just cut off the connector and solder the wires directly into the + and – holes for the battery holder. You’ll also want to omit the power switch and just solder together the holes where it would have gone.

The design's battery holder (Source: D. Mellis)

Mellis gave me permission to write about the projects and post some of the photos from his website.

Click here to check out all the files for this project.

Project Spotlight: “3D-Printed Mouse” Circuitry & Design

I get to meet and interact with creative engineers and researchers around the world who are working on innovative MCU-based projects. Some of them show up at our office to chat. Others I meet with when I travel to California for events like the Embedded Systems Conference. But many of the most interesting people and projects I find are on the Net. A perfect example is David Mellis, whose projects and research grabbed my attention recently while I was browsing the MIT Media Lab website. He is a PhD student in the High-Low Tech research group at the MIT Media Lab.

Mellis gave me permission to write about the projects and post some of the photos from his website, so let’s take a look at one of them—the “3D-Printed Mouse.”

The 3D-Printed Mouse design (Source: D. Mellis)

Check out the mouse strapped to a hand.

The mouse in hand (Source: D. Mellis)

Mellis writes:

This mouse combines a traditional electronic circuit board and components with a 3D-printed enclosure. The mouse is open-source: the original files necessary to make or modify its design are available for download below.

Download

Enclosure
Rhino: mouse.3dm
STLs: mouse-shell.stl, mouse-base.stl

Circuit board
Eagle files: mouse.brd, mouse.sch
Gerbers: mouse-gerbers.zip
Schematic: mouse.pdf

Component Datasheets

Button: SS-P_1110.pdf
Mouse Chip: ADNS2620.pdf

Code: hid-mouse.zip

Mellis notes that the circuitry and code are based on SparkFun’s ADNS2620 Evaluation Board, but “have been modified to include buttons.”

The first prototype with the SparkFun board (Source: D. Mellis)

Click here to access the project site.

 

Elektor June 2012: Nixie Thermometer, PIC Programmer, AVR Software-Defined Radio, & More

Elektor’s June issue is going to be a classic. You’ll read about a wide range  of topics from a Nixie thermometer/hygrometer to a PIC programmer solution to an Intersil IMS6100 vintage dev kit. And much more!

Watch the video below, and be sure to check out the Nixie tubes at the 6:50 min mark.

Here’s a summary of what you’ll find in the issue:

  • Nixie Thermometer/Thermometer: Nixie tubes are used in a retro-looking temperature & humidity meter
  • Preamplifier 2012 (3): A discussion of the LLLL board, the switch boards and the power supply board.
  • Flexible Stepper Motor Driver: If you have concerns about connecting a stepper motor driver to your PC, consider building this one with full electrical isolation.
  • Embedded Linux made Easy (2)
  • Computer-driven Heliostat: Here’s software and some electronics to enable you to use inexpensive servos to track the sun.
  • Dual Hot-wire Anemometer
  • AVR Software Defined Radio
  • Platino, controlled by LabVIEW (2)
  • Electronics for Starters (6)
  • PIC Programmer for Emergencies
  • 2-Wire Interface for Illuminated Pushbuttons
  • Retronics: Intersil IMS6100 Vintage Dev Kit (Series Editor: Jan Buiting)

CircuitCellar.com is an Elektor International Media publication.