# Platform 45: Electromechanical Feedback System

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What is this thing?

It's the highest level thing I've posted on here so far and uses sub-systems from a bunch of the other things I've put up. But it's still not at the point of being a usable system, so this is largely documentation that I'm laying down for part of the larger system, and it will make sense in context later on. This thing synthesizes a bunch of stuff I've worked on over the years. It is a rotational motor, and also a vibrational motor, a parametric mechanical amplifier, a massager, a musical instrument, and a chaotic pendulum. Really! And I've tested all this, at least briefly, but it will take some time to get videos that actually make sense up and in the mean time I need to have some record of the current version, so here it is.

This is an Instructable that only really makes sense as part of a network of instructions I'm posting on different sub components of a much larger overall system. What is shown here uses the Hexagonal HDPE Trash Coil, which is already published on here, the Trash Coil Drive Circuit, also already published on here, and the Amp Without PCB, which will be published next. It also uses basic cardboard and tape techniques shown in my Action Geometry stuff but also all over the place on this site from many users.

You need 3 Trash Coils, on Trash Coil Driver, and two Amps Without PCB, and one box of thick corrugated cardboard, as well as a steel rod, a small rare earth magnet, and miscellaneous tools(see Sub instructions mentioned above).

## Step 1: Cut Out the Cardboard Shapes

There are a few possible layouts, what is shown above is four 3 inch squares, two half squares, and one half square scaled up by 2x from the other two. In the final version I show later on here, I use a single small square instead of the large triangle. So I end up using a total of 5 3" squares and 2 3" half square triangles.

## Step 2: Cut Out Slots for Wires From Coil

As shown, draw lines with marker, use magnet wire with insulation still on to wrap coils tightly to three squares, and feed the leads through the slots to the opposite side. Be sure the ends of the coil leads are stripped with a razor blade all around on all sides(you probably already did this).

## Step 3: Use Clear Tape or Duct Tape to Assemble 3d Structure

As shown, fold it all up and use tape to hold it together.

## Step 4: Add Electronic Circuits

Driver drives one coil, the 10,000X gain amp connects to the other of the "bottom" coils, and the amp connects to the driver to make a feedback loop. A cut USB cable is used for power. Third coil connects to a 100X voltage gain op amp without PCB which goes through a DC block in the form of a 100 uF series capacitor on each of the leads going to an audio jack which goes to USB powered PC speakers.

## Step 5: Test and Deploy, Make More, Spread

I still don't have a reliable way to get the coil orientation right, so it's 50/50 if you get it right the first time and if you don't get oscillations, swap one coil orientation(doesn't matter which one) and try again.

If this makes little sense, wait for more details to come out both of sub-systems of this and of super-systems that use it to do things that are actually useful. Right now it's just a toy and a demo.

youtube video of noise making machine.

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