Random Find: The Avago/HP HDLG-2416

Anyone who’s ever visited Makerspace knows that the ‘Library’ is home to tons and tons of stuff.  Component parts, IC chips, belts, pulleys, batteries, etc.  Occasionally I lose myself in there for a few hours and just explore the shelves.  This is a post about one of my more interesting discoveries.

I came across a whole bag of these in the LED bins.  They’re 1″ wide, four-digit alphanumeric displays.  Each character consists of a 5 mm tall, 5×7 LED dot matrix display.  The device comes complete with on-board RAM and an ASCII decoder capable of displaying up to 128 different characters.  It’s even possible to dim the brightness.  I’m also partial to the color green.

The major drawback I’ve found is the number of pins required for use.  The thing has seven data pins and the extended features for writing/reading/displaying require a ton of connections.  I used all but four of my Arduino Uno’s I/O pins while tinkering with it.  You’re probably better off using a LCD display or something with serial data support, but these are still small and numerous in our ‘Space so they’re worth toying with.  Also there’s been a few other people who played with these and posted their findings online. I’m seriously considering building a small desk clock around one or two of these in the future.

If you’re interested in using one of these displays on your next project, I’d suggest reading the blogs by these fine folks here:



http://gorgusgfx.se/?page_id=62 (I think this is in Swedish, but the code still works!)


Magic Mirror Theater Prop

My sister is a Theater Manager at the Patel Conservatory in Tampa, FL.  About two weeks ago she texted me and asked if I could make her a prop she needed for an upcoming production.  “How keen would you be on making me a mirror for “Beauty and The Beast,” she said.  “They want a mirror that lights up and sparkles like the one from the movie.” Even with limited experience just tinkering around, I knew I could do something fairly easily, so I agreed and got to work.

I combined two different circuits (a 555 timer to flash and a RC circuit to fade) and built a wooden frame with acrylic plates for the front and back.  The wood and plastic were CNC-milled, then sanded and painted before the electronics were installed and glued into place.

The result was a fairly decent-looking, shiny, light-up hand mirror with a small thumb button on the right side that flashes 16 bright green LEDs when pressed.  It all runs off a single 9-volt battery and the back can be unscrewed to replace it should it ever die.

Total build time from start to finish was probably close to 15 hours over the course of one week.  The play was Thursday, July 19th and from what I’ve heard, it was a great success.  I’ll add pictures from the performance if I get some.

Wedding LED Unity Display

I’m getting married in less than a week from now. My fiance and I didn’t want to use a traditional unity candle for our ceremony, so I came up with something a little different. I used some RGB LED strips to create my own LED unity display.


The LEDs are controlled by a relay and two arcade buttons wired in series. When both arcade buttons are pushed the LEDs in the two smaller frames are are turned off and the LEDs in the large frame are turned on.


Completing this project required using the laser cutter, the CNC router, making my own PCB, and even a little bit of wood working to put the frames together.





A Simple Aux Input For iPod Speaker Systems

The first generation of Bose SoundDocks did not feature an aux input jack, they are only compatible with the 30 pin connector of iPods and iPhones.  Lately, my music player of choice is my Droid Razr, which has 60+ Gb of music on it, even more in the cloud, and no 30 pin connector.  I decided to add an auxiliary input to my SoundDock in the easiest and quickest way possible. I made an adapter cable using half of a $6 iPod extension cable, half of a $1 3.5mm headphone cable, and two necessary resistors.  I can plug this adapter cable directly into any unmodified SoundDock, or any other amplified speaker system that has a 30 pin connector.

It turns out that the SoundDock is smart, and will only power on when it senses 3.3VDC on pin 18 of its input connector.  Luckily, it also outputs 12VDC on pin 19 to recharge the attached iPod’s battery.  To trick the SoundDock into turning on with no iPod attached, I made a voltage divider by soldering a 20 Kohm resistor between the wires connected to pins 18 and 19, and a 4.7 Kohm resistor between the wires connected to pins 18 and 1.  The voltage between pins 18 and 1 was measured to be ~3VDC, which isn’t 3.3VDC, but is sufficient to power up the SoundDock.  I soldered the three pins of the 3.5mm headphone jack to the 30 pin connector’s wires as follows: Ground to pin 1, right audio to pin 3 and left audio to pin 4.  I used 1206 surface mount resistors because they measure only 3.2mm by 1.6mm, a size which fits conveniently under the shrink wrap joining the two cables.  The most time consuming part of this two hour project was identifying which color wires were connected to pins 1,3,4,18 & 19, and determining if the pin on the left of the photo was #1 or #30.

Makers, assemble!

Yeah.  Having access to a laser cutter is pretty boss.  I’m planning to wear this to the premiere of a certain movie this weekend.  Four layers of acrylic; two diffuse, two opaque.  11 LEDs, 11 100 Ohm resistors, some phone cord, some solder, and a 9V battery.  There’s no lack of great pages on Instructables about how to make your own.

PCB with Lasered Paint Resist and Fast Sponge Etching

TomG shows how he etches PCB boards using paint, a 25W laser cutter, Muratic Acid, 30% H2O2 and a sponge. Much frothing ensues.

The technique is a neat one, given the presence of a laser cutter, because it can take you from copper clad to etched board in a pretty quick amount of time.

One note, the Muratic Acid is actually from a pool supply store, not Home Depot. It is, of course, dangerous. Wear safety goggles, use gloves, use in a well ventilated area. (The acid smells like a punch to the nose, don’t inhale it)

The Critic

This is “The Critic.” It’s the USB accessory version of a red pen: Once armed by rotating the red safety cover up, the device is activated by simply flipping the toggle switch.  When connected to a computer via the convenient USB plug, it will begin to delete text, continually deleting until all the (presumably erroneous) text preceding the curser has vanished. At that point, the safety cover can be lowered, thereby deactivating the device.  The Critic is an indispensable tool for use when the document you’re editing is just so full of errors that your fingers begin to ache from holding down the delete key.  The Critic measures 3″ by 2″ by 2″ tall, and was designed to fit conveniently within arm’s reach, beside your keyboard or mouse.

I was inspired by the open source work of Pete at RasterWeb! and his recent effort to bring “The Button” to a wider audience of busy or non-makers.  He has freely helped tens of people create their own buttons, but is now able to fulfill requests for preassembled units. Among other applications, these USB buttons can be used as the shutter control of  Mac powered Photo booths at public events. These photo booths are powered by Sparkbooth, which can automatically upload the photos to Facebook, Twitter, tumblr or other social media sites.  His buttons emulate a keyboard, and contain an Arduino Teensy (only 0.7″ by 1.2″), which is a USB based AVR microcontroller.  Despite the Teensy cost of $16, I saw an opportunity for cost savings by opening a standard USB keyboard and spending a few minutes to extract and reverse engineer their compact circuit board.  Although this isn’t a solution suitable for even small scale production, it can work for a one-off prototype, like The Critic.

Below are several photos that show the process of opening the keyboard to extract and modify the circuit board.  When the top of the keyboard is removed, a sheet of silicone ‘popples’ is revealed.  These ‘popples’ are the springs under each of the keys.  Under this layer are two sheets of thin plastic, one with conductive ink traces that are (mostly) horizontal, and one with conductive ink traces that are (mostly) vertical.  These layers of traces are separated by a small gap.  When a key is pressed, a protrusion on the bottom of that key’s popple pushes the two layers of plastic together at this location: connecting one of the vertical traces to one of the horizontal traces. These traces are routed to the circuit board via a row of contacts under the front edge:


The chip (under the black epoxy potting on the bottom of the board) detects this electrical connection, and outputs the appropriate character over the USB cable.  The keyboard, popples and plastic layers can all be replaced by an external switch and wires soldered directly to the circuit board.  The photo below shows wires (whose free end is to be connected to the switch) soldered to the pads required to output a space bar character.  To output other characters, simply follow the vertical and horizontal traces to the board, and solder wires to those pads instead.


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My neverending quest for quick turnaround prototype PCBs

For years I have dreamed of a fast way to prototype PCB for projects I am designing.

20 years ago I was using rub on drafting tape and stencils – slow and spotty results.

I tried to modify a plotter to plot resist directly to a PCB – no luck.

Magic markers – I’m no artist.

5 years ago I hacked a laminate router by tapping into the stepper controllers and adding a better Z axis – It can rout boards ok, but takes some tweaking.  It only does fairly wide traces.  But its great at drilling holes!

2 years ago I tried the inkjet printing systems – lots of smeared wet ink and poor registration, not very effective.

I opened up a laser printer and tried to get a board to go through it – almost worked, but the fuser was to narrow to take the board.

Although I haven’t found a fast system yet, I get by with the PNP Blue material and a good laminator.  Although I am regularly disappointed when dust, not quite clean boards, minor wrinkles and other issues leave gaps in traces that need touching up.

Which brings us to the latest attempt:

Now that the maker space has a small laser cutter I am trying to find something I can coat a board with and either burn away or melt onto the board to act as an etch resist.

Early attempts with paint had moderate results – our laser cutters on only 25W so it didn’t burn it cleanly.  I have heard that using flat black paint and a more powerful laser works.

Paste wax and markup fluid weren’t dark enough for the laser to vaporize (thinking of trying black crayons)

The latest attempt uses laser printer toner (just like the PNP only skipping the printing and iron on steps.)

The problem is how to get an even coat on a board without it blowing around.  Static electricity has potential (just like what they do inside a laser printer) but I don’t like the idea of a 5KV power supply exposed and handling powered toner is an automatic mess.

So for the first attempt I mixed the toner with rubbing alcohol (30% water).

Messy stuff!

I painted it on with the tongue depressor but it seemed to coat evenly and took only a few minutes to dry:

It mixes well and paints on fairly easily, here are some sample prints I did at various power and speed settings.  I cleaned the board fairly aggressively with paper towel and rubbing alcohol.

None are quite clean enough to become PCBs but they are getting close.

Although the toner paint looked dry, it may still have had some water in it.  I plan on trying a batch with denatured alcohol (100% – no water) and see if it works better.



Updated progress

I have been trying a number of materials and methods to make my fast turn circuit boards.

I’ve decided that last toner is too messy and there are too many variables to create a repeatable process.  So now I’m trying various other masking materials:


Black and white spray paint – it works ok, but the ash left behind by the laser resists the etchant and leaves you with a poor etch.

I also tried tape:  Painters tape, electrical tape, clear and brown box tape.  The masking tape worked ok until the etch was slow and the tape started to dissolve.

I held a few of the boards up to the light so you can see how it etched:







One of the other members of the space found someone who had made the black paint work.  The process is to do 2 passes with the laser – the first burns off the paint, the second burns off the ash!  Then you wipe the board down with rubbing alcohol to clean off any residue.   Here is a set of 3 projects I lasered and etched at once:

This board turned out rather well, I had some trouble with the etchant taking for ever so lost some of the detail on the lettering, but the boards came out nicely.  I should get even better results on the next project.

In an attempt to speed the entire process up I tried to drill holes with the laser cutter from the back of the board:

   Not very good results!  After about 6 passes it still didn’t cut through thin PCB material and stunk and smoked the whole time!







So instead, I used the laser to cut wholes in a small piece of acrylic to use as drill guide:




This gives you a pattern to follow using a Dremel and the holes wind up in the right places and nicely lined up.  I drilled 2 holes in opposite corners of the board and used the leads from resistor to line up the template and board and hold them together while drilling.




This image shows the template attached to the board and about half the holes drilled.  This worked very nicely!  The only problems was small disks of acrylic getting stuck to the drill bit (you can see little craters on the left side of the board where these came from)  I had to clean the drill bit twice to drill the whole thing.  Either bigger holes or a different plastic might fix this.


This is first of the 3 boards I put together and it works just fine.  It is a level translator for the encoder you see in the holder.  The encoder will be attached to the drive motor in my electric car and feed back motor position to the controller.  The encoder is 5V and the controller wants a 15V signal.  The test bed uses a 15V power supply and LEDs on the 4 quaderature outputs.

Encoder test video

The Library

The Library

If you’re ever at the Milwaukee Makerspace and you hear someone say “It’s in the Library!” you might wonder to yourself (much like I did) why it’s called the Library.

Yes, we do have some books in there, but we’ve also got a giant wall of electronic components, as well as a sewing machine, embroidery machine, computers, projects, supplies, and miscellaneous junk.

I ran the question past Royce, and he had this to say:

It’s because we have a library of electronic components.

For example, if you are reading the Arduino Cookbook and a circuit in there calls for a 47uF capacitor or a 2N2222 transistor that you don’t have, you needn’t pay $5 shipping for a 50 cent part and wait three days to boot. It’s almost certainly in our parts library. Just go grab it!

We have most every value of through hole resistors and capacitors in a variety of working voltages. We also have common discrete silicon devices such as diodes and transistors. We are more limited on the ICs because of the colossal variations in ICs, but we have a lot of common beginner type stuff such linear power regulators, silicon controlled relays, 74 series logic, the venerable 555 timer, RS-232 level shifters and more.

So there you have it! Sure, there’s some books, but mainly it’s a “library of electronic components” which for a hackerspace, is a pretty awesome thing to have.

XBee Breakout Board

I recently purchased a couple of XBee modules from Sparkfun for a new project I’m working on.  I’ll be using them to send a wireless signal from an ice fishing tip up when a fish is on the line. I was frustrated after I received my XBee modules because I realized they do not fit into a standard breadboard!

After I got over the initial frustration I started designing a breakout board that would allow me to use the XBee modules with a breadboard. I used Dip Trace to design my first two sided board.


After I got everything laid out in Dip Trace I etched the board using the equipment at the makerspace. I used our standard process for etching the board.

  1. Print the board design on press and peel blue using a laser printer.
  2. Transfer the circuit design from the press and peel to the copper clad fiberglass board using a heated press.
  3. Etch the board in ferric chloride.
  4. Drill all of the pads with a #65 drill bit using a Dremel.


Here is the finished breakout board.