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And now for something completely different – a Dollar Store Dissection.

To electronics hobbyists, dollars stores aren’t just a source of cheap gadgets that break easily — they are also a source of fresh cadavers for dissection.  In addition to giving us insight into the design and contruction of cheap gadgets that break easily, the dissection provides very cheap electronics parts (which don’t necessarily break easily).

As a robot builder, I’m drawn to anything that is battery operated and moves, since that almost always means that I’ll get a low voltage DC motor for my dollar.  On my last trip to the dollar store, I nabbed a couple of battery operated fans. 



These babies have an "LED Color Matrix" which, according to the package, form 64 different patterns (I didn’t count them) and are great for "disco party" (haven’t tried that yet).

The case was held together by a single screw in the battery compartment.  When the case was opened, the innards spilled out.  A pretty good haul for 30 seconds work: a DC motor, a toggle pushbutton (which are remarkably expensive when bought new), and a case that will make a nice LED flashlight, methinks.



The sharp-eyed reader will have noticed:
 a) The fan case changed colour from green to red. I’m saving the green unit shown previously for the aforementioned disco party.
b) The motor has a resistor and a small filter capacitor, presumably because the 4.5 V of battery required by the disco lights are a little more than the motor can handle.  I think it’s quite nice that they bothered to add the capacitor.
c) The fan is sold by ACME Toy Company.  I probably shouldn’t try to catch the Roadrunner with it.

That’s all well and good, but hardly worthy of a blog posting.  So let’s move on to the advanced technology which gives the fan its name: the LED Color Matrix.



Behind the nose cone of the fan lies a small circular white circuit board.  Attached to the board is a ribbon strip of surface mount LEDs of various colours. 




















The front side, shown on the left, has several different test points (not solder pads, as I would learn) on the circuit board, but the only ones that appeared to be hooked up to anything are the two that I’ve marked with a "+" and "-".  There is also an epoxy covered chip which, presumably, is responsible for generating the acclaimed 64 colour patterns.  I must admit that I didn’t dare try to remove the epoxy, for fear both of destroying the LED strip’s functionality and of drawing the wrath of the ACME Toy Company’s lawyers.  

The reverse side, as shown on the right, had 2 solder pads and 2 test points, but they all appear to connect to ground.  

Originally, I had planned to make the LED strip more usable in future project by soldering leads to the positive and ground test points.  (In situ, the circuit board was powered by pressing it against leads from the battery).  For reasons that I admittedly don’t understand, the LED strip wouldn’t work after I added the solder – touchy! So, I hastily desoldered, and had to switch to using the bare metal in the middle of the board as the ground for the following photo.

Trial and error showed that 3 volts was enough to get the green and red LEDs glowing and blinking.  At the full voltage of 4.5, the blue LED joined the party.   The top secret chip does it magic by varying the blinking pattern and intensity of the lights.  Presumably, the other 2 LEDs won’t light because of some damage that I did to the circuitry when I attempted to solder it.

The package actually indicates that there are 2 models: one that takes 2 AA batteries, and the one which I got, which takes 3 AAA.  It would be interesting to learn how the 3 V version differs — less flash, or more advanced circuitry?  Perhaps that model is for less flashy events than a disco party? Tea party?  Inaugural ball?  The mind reels at the possibilities.

Admittedly, though, my mind has failed to think of a use for the LED strip yet, especially given its resistance to soldering.  Still, the other loot — especially themotor and pushbutton — made this a dissection well worth doing.