Super-Animal Soundcard. Make your own sounds !!

Summary: This post discusses a simple,inexpensive Sound Card that reads bar codes and is used to generate animal sounds from animal-trading cards provided through our local supermarket chain. The post shows how you can make your own bar codes to create the sounds without (or in addition to) the cards.

Intro:  Collectable cards are a favorite again (right).

Our local supermarket giant (Woolworths) has started giving away cards with purchases above a certain value.  Theses card have animal pictures, names, a "did you know ?" question and Question/Ans section.

A nice feature of these cards is they have a bar code on the back (see image below).  With a purchased card reader (AUD$6) the card reader makes the animal sound associated with the animal when the bar code is swiped through the reader.

Our idea was, could we get the Sound Card to make a sound of an animal from a bar code that we created ?  We started by looking at all the bar codes lined up as shown below.  The bar codes all show a very similar pattern (try it if you have your own cards).  There are 13 bar code lines over a distance of 52 mm, so that the spacing between each line (called the pitch) is 4mm. 

 The first 3 lines are always very thin and the last  line is always fat.  These are typically referred to as START bits and STOP bits.  Combinations of thin and fat lines in between the start and stop bits tell the Sound Card what sound to play.  We started by using a black sharpie pen (from any stationary store or newsagent) to draw lines on thick card stock (around 220 gsm).  Thin paper generally doesn't work (see later for explanation).  If your very careful, you can get hand drawn lines to work, but the lines must be drawn very carefully.  Start by trying to copy the lines of an existing card that you have.  Some of our examples are below.

 We found it hard to make sounds consistently (all the time) with hand drawn lines.  So we created a template which you can download and print on thick card stock (~200gsm, again available from stationary stores an some newsagents).  Be sure when printing that you do not select "Fit to page".  You must print the original size of the bar code pitch will change.  When we used this template to create new bar codes, the results were much better. 

Things to try:  Randomly make some of the lines thicker between the start bit (3 first thin lines) and stop bit (thicker line on the end).  If it makes a sound, then try to find the corresponding card from your collection.  BETTER STILL, we'd love to hear from any one who has found a bar code that makes a sound  that does not belong to any card !  Some software programmers often put these special bonuses into their programs and call them "Easter Eggs".  They are most often found on CD's or DVDs, but I'm interested to know if there is an Easter Egg on the Sound Card reader.

Template for creating your own bar codes (use the pdf provided).  The bar codes must be printed on thick (200gsm) card stock to activate the switch in the Sound Card (see How it Works below).  The template contains the correct spacing of lines. Tthe 3 start line and stop line should not be altered when you make your own.

How it works 

The image below shows a card in the Sound Card reader, with the back of the Sound Card open. 

Figure:  Center - Opened Sound Card showing the on/off switch and bar code Sensor (operational detailed in image below).  To the left, larger image of the Switch and Bar code sensor, To the Right - larger image of the memory chip containing all the sounds.

As the card passes down the reader, it presses against a micro-ON/OFF switch (see below in more detail).  This turns the Sound Card on only when the card slides down the reader, and means that the batteries are not wasted when the Sound Card is not being used.  It's also the reason you need to use thick card stock (200gsm) for the bar code paper, as  regular paper is too light and will not push hard enough on the switch to turn it on.  After the micro-switch turns the Sound Card on, the bar code passes by a Bar Code Sensor.

 This Bar Code Sensor consists of a light source (called an LED which stands for light emitting diode) and a light source detector.  The LED emits infrared light (IR=infrared).  The IR light is invisible to your eyes but some cameras can see this light - ask your parent/guardian to try using their phone camera to see the light just as the card passes the sensor (it's a very weak light).  Also use the phone to see if your TV remote control is working (they use the same wavelengths) - i-phones may not work to view this light as some use a filter to block this wavelength of light.  An illustration of how the bar code sensor works is shown below [Source].  When the IR light (from the LED) passes by a white section of the card, the detector sees the reflected light and reads this information as the code "1".  When the light strikes the black portion of the card, no light is bounced off the card, so the detector sees no light, and reads this as a "0". 

Figure : Illustration of the LED (IR transmitter) and detector (IR receiver).  IR stands for Infrared and means that you can't see this light with your eyes (however some digital cameras can see this light) - Image Source

    So when the whole card is swiped past the Bar Code Sensor in the Sound Card it reads a code like 11101101001100101011111.  It then looks this code up in a list (often called a database) where it finds the correct sound for the animal.  An example list I made up is shown to the left (the codes are not correct). Using the code the brains in the Sound Card looks up and finds the correct animal/Sound from the list and then plays that sound. 

In the figure above which shows the opened Sound Card, the brains of the Sound Card (a small microcontroller) is covered up by this blob of black goop.  Manufacturers use this goop to cover up he part numbers to reduce the chance of someone reverse engineering the technology.  Actually, all the sounds (stored in the database) will be stored in the 8-pin chip (25L1605D) shown on the right of the image above (next to the opened Sound Card).  This is a 16M-Bit CMOS serial flash (technical datasheet).

 Let me know if you find any easter eggs using your own bar codes, or if you have any ideas on how you might use this Sound Card differently.  A great learning experience for AUD$6.  Please ask a parent or guardian before doing anything like taking the Sound Card apart.

NEWSFLASH:  We've recently found that Card #15 (Grater One-Horned Rhinoceros) makes what we think is a bird sound and the Southern Cassowary (Card #33) makes a grunting sound.  Did Woolworths mix these two sounds up in the soundcard reader (market name SoundKard) internal data base ? I suggest checking other cards for inconsistencies otherwise you or your children could grow up with a very distorted view of how animals sound.!!  Let me know if you find any other errors in these cards.

Adrian