Flash Animation
Flash Animation

Happy Halloween Everyone!
I heart oscillators! This project is born of a workshop that I'm running in Brooklyn, NY at 3rd Ward. I'm teaching an ongoing series of basic electronics workshops called Electro Lab. Each time I do it, there is a theme. Last summer (2010) it was the Robotics Edition. This fall, it's Halloween Edition, and this circuit is the culmination of our work.

Note: This Instructable will be amended with video and more notes at the end of the workshop. For now, enjoy dorking out at the 3-D oscillator!

If you've ever done much work with a 555 timer, you know that you can make sounds (A-Stable), and also that you can turn things on (or off) for a given amount of time (Mono-Stable). Some of you may have even gone as far as creating a warbling siren. This Halloween, I wanted to make a spooky sound.... like the kind the ghost makes on Scooby Doo. It's a low tone, that raises and lowers pitch slowly, and has a kind of vibrato. "Perfect", I thought, "I'll use a 555!". Well, a pile of 555s more like.

I found a few examples of tone modulation online, and this one gave me the variation in tone that I was looking for to slowly raise and lower the pitch. The basic idea is to connect the first 555 Threshold/Trigger pins to the second one's Control V pin and send a low freqency wave that occurs as the capacitor charges and discharges. That works great, you get a nice US police siren warble.

Then, I needed to add that creepy vibrato, so I looked around and found a few other ways of adding oscillation to my oscillator. Here is an example of a type that takes the Output of one timer, and ties it to the Discharge pin of the second. That makes the tone change in pitch, like a Euro police siren (bee-boo-bee-boo). I played around with the wires and found that if I connect from the Threshold/Trigger pins, It worked to smoothly change the tone! Then I added the Monostable circuit to control the on duration of the audio.

I've got a picture of the circuit, and a schematic to follow along. It's all been double checked, I promise. More accessories, including an IR doorway switch to turn it on, coming soon!!


Step 1: Spooky Sound Machine Schematic

This is a working schematic for the Spooky Sound Machine. It has been triple checked for errors ;]
Click the [i] in the upper corner to see the image without the yellow rectangles.

Step 2: Spooky Sound Machine Breadboarded

Here's a nice clear image for those who want help breadboarding or troubleshooting their work.
In your schematic I couldn't read the values, but it looks interesting.
I'm finding it hard to find .01nf and the .047nf. I'm putting your circuit with another 555 timer circuit that acts as the skeleton's eye's, an Arduino Uno, and a Parallax PIR Sensor. Going to be great for halloween :).
nice instructables.. but i thought the project is made up of 555 timer, but i see in your project is 556 timer. my i ask for a schematic diagram using a 555 timer?<br><br>thanks...
<br> The 556 is a dual 555 timer. It gives you two Discharge, Trigger, Threshold, Reset, Voltage Control and Output pins. Here is a link to the <a href="http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS007852.PDF">datasheet</a>. All the pin connections in the diagram above are for the 556. If you want to, you can co-relate the pin connections to the 555 IC and build the same circuit with 4 555s.<br>

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