LED Micro-Readerboard, version 2.0: FAQ File

Frequency asked questions for version 2.0 of the LED Micro-Readerboard project; this list will expand as we get asked more questions. ;)

If you don’t find what you’re looking here, you might consider asking a question in the forums.

Where can I find ____ about the LED micro-readerboard project?

Helpful links:

  • Project Overview: here
  • Datasheets & technical reference data: here
  • Assembly instructions: here
  • Source code: here
  • Support: here
  • Buy kit: here
  • Information about the old (v 1.0) version of the project? here

 


What is the LED micro-readerboard?

Our LED Micro-Readerboard is a fun little open source project that provides an introduction to the capabilities of microcontrollers. Once assembled, the readerboard spells out simple preprogrammed messages such as “MAKE,” or “HELLO WORLD,” one letter at a time on its alphanumeric LED display. With the default firmware, fifteen phrases are included and a bank of optional holiday messages can be enabled as well– in case you want to use it as a holiday ornament.

The kits come with pre-programmed microcontrollers, so no programming is actually needed– making it a simple electronics soldering project. Assembly is easy with comic book style instructions.


What’s new in version 2.0 of the kits?

Mostly battery life. The LEDs in the old version were not very efficient. In order to make the display bright enough, the LED segments had to be run with a surprisingly high duty cycle and drained the batteries very quickly. In the new kits we use a new highly efficient display, which allows us to run each segment on the LED with relatively low duty cycle.

The second significant change is that we went from using a common-cathode LED display to using a common-anode display; this requires some simple wiring and firmware changes, see technical data for more about those changes.

Aside from those, there are a number of other places that we’ve cleaned up the code, and we (finally) have proper packaging for our kits.


What *is* the battery life of these things?

That depends how you use it. ;) With the default firmware, you should typically expect it to run for at least three weeks continuously on a set of two new AA alkalines, if near room temperature.

If anyone runs one long enough to test the battery life, I’d be interested to hear what you found.


Why isn’t the battery life longer and/or why isn’t the display brighter?

Nearly all of the energy stored in the battery is used to light up the LEDs. So, there must be a trade-off between running the LEDs brighter and having the batteries last longer. (Stupid laws of physics!) While we’ve played with a lot of different brightness levels, we settled on this one that looks great in most indoor lighting conditions and only starts to look dim in a very brightly lit office. At the same time, it should be energy efficient enough to keep the typical battery life at three weeks or more.
If you’d rather run brighter for less time or dimmer for more, you are of course welcome to tweak the firmware to suit your desire.


How do you get started programming AVR microcontrollers?

Look here and here. (That is a lot of information.) If you need more hints, click the “Forums” link up at the top of the page and ask your questions there.


What phrases are in the default firmware?

The firmware contains a list of phrases. Each time that the unit is turned on, it picks the next one in sequence to display. Normally, it cycles through this bank of phrases:

 PLEASE CHANGE MY BATTERIES    JUST KIDDING   HAVE A NICE DAY
 HELLO WORLD
 I SOLDERED THIS MYSELF
 MAKE   TECHNOLOGY ON YOUR TIME     MAKEZINE DOT COM
 HELLO   I AM AN OPEN SOURCE MICRO READERBOARD
 MAKE
 MAKE IT
 THIS DISPLAY USES ONE HUNDRED PERCENT RECYCLED ELECTRONS
 MAKE DONT TAKE
 MAKER
 MAKE STUFF
 EVIL MAD SCIENTIST DOT COM
 I HEART ELECTRONICS
 DUDE    NICE BLINKYLIGHTS
 JOIN THE RESISTANCE      USE KIRCHHOFFS RULES AND OHMS LAW

If holiday mode is turned on, the following additional phrases are also enabled:

 A SUBSCRIPTION TO MAKE MAGAZINE MAKES A GREAT GIFT
 THESE ARE NOT THE PRESENTS YOU ARE LOOKING FOR   MOVE ALONG
 WARNING  WARNING   THIS TREE WILL SELF DESTRUCT
 I AM IN UR TREE BLINKIN UR LITEZ
 ORNAMENT
 LET IT SNOW  LET IT SNOW  LET IT SNOW
 I HOPE YOU SAVED SOME PRESENTS FOR US ORNAMENTS
 HAPPY NEW YEAR
 ALL I WANT FOR XMAS IS A MICROCONTROLLER PROGRAMMER
 I AM THE VERY BEST ORNAMENT ON THIS TREE
 SANTA CLAUS IS COMING TO TOWN    LOOK BUSY
 BAH  HUMBUG
 ALL YOUR GIFT ARE BELONG TO US
 HAPPY HANUKKAH

Finally, there is one additional built in phrase, “I AM SHOWING OFF MY PROGRAMS” that will cycle through all of the enabled phrases in sequence and repeat.


Do I have to buy the kit to build this?

Nope. It’s an open-source project. Get the parts, download the firmware & modify as you see fit, program your microcontroller, download our comic-book style instructions and have fun!


Can I buy the kits and then reprogram them to suit my nefarious purposes?

Yup. Go right ahead. =)
Let us know if you do something cool with them!


Is there anything in the chips that prevents them from being reprogrammed?

Nope. Go right ahead.


Can I build it with a socket?

Yup, go right ahead. Use the socket in the instructions as you would the microcontroller, and put the microcontroller in at the very end. If you do this, use either a DIP-20 solder-tail socket or a DIP-20 wire-wrap socket; machine pin sockets will make things tricky. If it’s too tricky, you might consider putting both the LED and the socket on a little protoboard, facing the same way.


I have a kit, but I don’t know whether it’s “version 1″ or “version 2″. Which do I have?

v1: LED display has grey face, instructions say “holiday electronics projects”

v2: LED display has black face, instructions say “MAKE”


Can I still download the instructions and code for the old version of the micro-readerboards?

The old instructions are here. (400 kB PDF)
The old firmware is here. (Please note that the old code is obsolete, and the revised firmware has switches in it that let you configure it to work well with the old kit hardware.)


How do you use the source code?

You need a (hardware) programmer and a working installation of AVR-GCC, or one of the programming environments based on it. In case you use one of the many programmer supported by avrdude, you can even use the makefile included with the source code.

To use it, follow these steps:

  1. Update the header of the makefile as needed to reflect the type of AVR programmer that you use.
  2. Open a terminal window and move into the directory with this file and the makefile.
  3. At the terminal enter
    		make clean   
    		make all     
    		make install
  4. Make sure that avrdude does not report any errors. If all goes well, the last few lines output by avrdude
    should look something like this:

    avrdude: verifying ...
    avrdude: XXXX bytes of flash verified
    
    avrdude: safemode: lfuse reads as 62
    avrdude: safemode: hfuse reads as DF
    avrdude: safemode: efuse reads as FF
    avrdude: safemode: Fuses OK
    
    avrdude done. Thank you.

If you do use a different programming environment, make sure that you copy over
the fuse settings from the makefile.


What other LED options do I have besides the suggested ones?

If you’re willing to modify the code a little bit,
Radionics has a very similar display, the Kingbright PSA08-12EWA, (Stock No. 451-6622) which is a common cathode display, but of a slightly different configuration.
You could also rewrite the font table to use a smaller 14-segment display, like part No. ANC-392 from All Electronics, or change the code more substantially to drive a 5×7 LED matrix, like part number LED1112 or LED1115 from BG Micro.

Finally, if you have nothing but old, dim, and boring LEDs, you can certainly arrange discrete LEDs in the same pattern; it might be best to use rectangular-shaped LEDs or to use two LEDs (driven in parallel) for each segment. If you’re willing to modify the code a little more, you can also consider using any number of other available dot-matrix or other alphanumeric LED devices. It’s just a matter of tweaking the font table a bit.

Do you sell kits with customized phrases?
Do you sell pre-assembled customized micro-readerboards?

No, usually not. But if you really really want customized or preassembled kits and you don’t want to do your own programming and/or soldering, you might ask anyway. Igor is sometimes willing, for a fee.


Drive LEDs without resistors? Are you crazy?

Hey, they don’t call us Evil Mad Scientists for nothing, you know. ;)
Actually it’s not crazy, but you do have to pay attention to the currents and voltages that you are using in order to be sure that the average current stays at a safe level. Resistors are usually used in series with LEDs for good reasons, so don’t go taking out the load resistors that you use in all of your other LED circuits.

Important note on that topic: If you hook up your microcontroller to more powerful source than the two alkaline batteries that we suggest, you are courting danger– be sure to use dropping resistors.


Can I drive the Micro Readerboard with NiMH rechargables or a 3V lithium coin cell?

Probably, but we don’t promise anything. =) NiMH cells have a lower voltage so they will definitely be less bright, and could possibly cause an undervoltage reset on the microcontroller. In our tests, they worked, but were indeed much less bright. Our past experience with lithium coin cells leads us to expect that they don’t always source enough current to run this project… however, we did successfully test a standard CR2032 lithium coin cell– and it worked quite well, albeit with reduced battery life. Our take on this was to make wearable name tags out of them.


Are any alternate sets of firmware available?

Yup. At least two. This one looks pretty interesting. We’ll be adding a few additional programs here when we get a chance (one of them– a POV version– totally rocks). If you develop other programs that can do something interesting on the tiny display, let us know and we’ll include it in the list here.    
Are any alternate sets of instructions available?
 Yup. Here is the article from MAKEKits on Instructables. They show you how to use a socket in the build, and how to reprogram it using WinAVR (on Windows, of course). If you want to build it with a ZIF (zero insertion force) socket, you might want to take a look at this too.


Where’s my obligatory warning? I want my warning!

Okay, okay, right here!

All projects, activities, and kit materials suggested and made available through evilmadscientist.com are provided solely in the hopes of providing entertainment, enjoyment, and education. And as they say, it’s all fun and games until somebody loses an eye. We cannot supervise you. Your safety and compliance with the law is fully your own responsibility. Always use common sense and appropriate safety precautions. Tools, heat, chemicals, electricity, foods and things-not-in-this-list can all be extremely dangerous if not used correctly. Minors should not attempt any projects that we describe without supervision by a responsible adult. Use of our instructions and project ideas is at your own risk and we disclaim all responsibility for any and all resulting damage, injury, or expense.

Soldering irons, hot glue guns, and things that have recently touched them can be extremely hot; you can burn yourself, someone else, and even set fire to large expensive things that you did not intend to. And wear eye protection.Keep in mind that it’s possible to cook (destroy) both LEDs and microcontrollers with a soldering iron, so please solder carefully and do not choose this project as your first “learn to solder” kit. If you haven’t ever used a soldering iron, this would be an excellent time to seek help from someone who has. If you think that you might make mistakes while you’re assembling your kit, you may want to order an extra one to begin with– you’ll save the cost of shipping that second box.

If you are in doubt about whether this project is for you, you may want to skim through the kit instructions before ordering a kit or a set of parts.

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