August Waning...

August is on the wane (ok..ok... end of August) and I am in my design process for this year's Halloween props and decorations.

I got new Gemmy skulls from Lowe's....they are different than what they made last year.  I think last years model was better but a lot heavier....this year's model has these round eyes that light up.  On the web there are some models where these eyes move and light up..

I will be hacking these, this is what these look like:

 Here is what it looks like with the 4 screws removed....

How these work is they have a dc motor that spools a thread that is linked to the jaw lever...energize the motor and it spools up the thread and opens the jaw.   Voltage removed and the spring tension on the jaw closes it....very simple.   They have a circuit card with some sort of custom microprocessor chip that drives the sound with a custom series of sounds, plus drives the jaw and eyes.  There are inputs, one from the switch that comes with it for testing, a photocell that is between the eyes and a microphone that is a silver disk in the back of the skull that reacts to sound.   Either sound or shadows can activate the device.  I will be harvesting these boards for possible use later for triggers and what not.   If the output can drive dc motor, it can drive a relay coil so I can use it for triggering other effects (one day).

If you wish to hack these you basically cut the wires to the motor and tie that into a voltage source (like a relay with 5 vdc powered through it) and tie that into a light organ.  A light organ takes sound and converts that into voltage.  I will be using 2 Mr Christmas Digital Musical Light Show.  It cannot drive too much power but I tie the AC output and drive an AC coil on a relay (from Radio Shack) that switches DC power that ties into the motor and eyes.  You do have to include a resistor in series with the eyes or you will burn out the led eyes. 

Best site for hacking the Gemmy skull is, they are promoting their midi interface but for $45 and driving 2 skulls that is actually not a bad price at all:

Automat3d Gemmy Hack


Here is rough sketch of the Gemmy Skull circuit wiring.  The wire color may change and there is 2 wires going from and to every component:

As the wiring colors may change just be aware but this is what I rewired the above to be. I used the try me switch as my input port for power from the relays that I am driving the skull circuit with. So if there is a problem with a skull I can just change it out by unplugging the try me connector and swap out the skull.  For the connections I simply soldered all the connections and wrapped the connections in electrical tape.  I taped the wiring inside the skull to keep it away from the jaw motor lever machinations.

 

I have 2 Mr Christmas Digital Light Shows (MCDLS) where my left channel from my mp3 player audio output is connected to one  MCDLS and the right channel drives the other MCDLS.  I bought a couple of AC coil relays and drive those that switch on command DC power to the above skull(s). The relays essentially have their coils driven by the MCDLS whose contacts switch DC power to the skulls.  Its kinda clickity clackity with the sound, I have put the relay box inside a couple of boxes for sound proofing as I run the wiring from just inside my double door front door out under the jamb and up to the door header where the skulls are.

I still think if you are working from scratch, the above noted Gemmy midi link Automat3d Gemmy Hack is best way to go so far that I have seen.   The problem with some of the other hacks they use a Pulse Width Modulated signal to drive servos, that wont work for these simple dc driven skull motors that Gemmy uses.


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