# Having trouble with my Gemmy skull hack...



## Ryan Wern (Dec 3, 2009)

Some people on here gave me a schematic for a circuit to drive the DC motor on my Gemmy skull-dropper that I'm trying to hack. What I'm trying to do is feed audio into the skull and have the jaw move along with the new audio. I built the toy motor circuit, and it appears to be working ok, but the problem is that the motor on the skull does not seem to be able to overcome the spring the closes the jaw now. I guess what I'm saying is that the motor tries to turn but can'topen the jaw against the spring. I'm feeding the DC motor 6 volts DC, which is the same as what the batteries provided. I was wondering if...

1. The input audio signal needs to be stronger

2. I need a softer spring to replace the factory one

3. There is something else that I missed...

PLEASE HELP! I know it's only February but I have big plans this year! I need to get these props going.


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## hedg12 (Jul 6, 2008)

Was this the circuit you used? If so, it needs a good strong speaker level signal to drive it. What are you using for an audio source, and how is it connected?


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## Ryan Wern (Dec 3, 2009)

Yes that's the circuit I used. I'm using a small home stereo for the source. I just tapped into the speaker wires coming out of the amplifier. I'm very familiar with audio and I thought that maybe the audio signal was the problem. I was thinking of using eighther a large home receiver or a 12 volt line driver to boost the voltage of the audio signal. What do you recomend? I did a garage haunt last year with all human actors, but I'm new to the whole animatronic haunt thing and I have big plans this year. I'm beefing up my walls (we had people literally run through a few of them last year, the chainsaw scare gets 'em every time!) and building a handfull of animatronic props (this skull project, a cauldron-stirring witch, a ground breaker skeleton so far) along with LOTS of new static props and improved lighting. I'm going to build a walk-through yard haunt geared toward young kids and another garage haunt which will include the huge, paved side yard of my new house for the big kids and adults who REALLY want to be scared. Great forum. This is where I get most of my ideas from! After last year, I've become known as the "haunted house guy" in my neighborhood. Thanks for the help


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## Dr Morbius (Sep 21, 2004)

I've built a couple of those circuits and they work good provided you have a very good amplifier and a power supply that matches the voltage of the original prop but with extra current available. It seems this circuit sinks more current than the original props motor needs to operate. If the original prop uses 2 AA batteries at 1.5V ea =3V then use an ATX power supply tapping off the orange wire (3V side). These power supplies provide ample current to make the motor work with this circuit. If after using a power supply with enough current and it still doesn't work, you need a better amplifier.


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## Ryan Wern (Dec 3, 2009)

Dr. Morbius,

Thanks for the insight. Here's a stupid question...what's an ATX power supply and where can I get one? I'm pretty new to this stuff and not a genious with computers or 120v AC electrical stuff. I'm figuring it out thanks to you all. Give me 12v DC and a car and I'll make it work, but my knowledge is limited on this stuff.


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## hedg12 (Jul 6, 2008)

The good Dr. is referring to a PC power supply. They can be had very inexpensively (even new) and can be easily modified.

I used one of the toy motor circuits last year with good results. I used a 6V wall wart and an amplifier from an old set of PC speakers. Worked very well.


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## fritz42_male (May 5, 2009)

The Cowlacious sound to servo board now also comes with a high current drive for motors. I also bought a dual port box off Jim Kadel (http://hauntmasterproducts.com/) who designed the original circuit that hedg12 referrred to - haven't set it up yet though.

The box I bought from Jim is similar circuit wise but has a 555 timer in it that looks as if it is set up to extend the jaw opening 'pulse'


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