Mechanical and electrical systems, part 2. The booger trap.

In part one, we introduced the booger trap and explored internal mechanical connections of components. In part two we’ll spec out the trap.

The booger trap has three main interface components, and one “internal” component. First, we’ll explore each component individually, and then we’ll figure out the connections between components.

• Trigger
• Speakers
• Controller (probably an arduino or a raspberry pi or something)
• Booger Storm Mechanism

Trigger

We need to determine if the victim is in the area of effect or not. That’s it, we just need an affirmative response when we have a victim, and we want to reduce false positives (boogers fly and nobody’s there) and false negatives (somebody is there and we didn’t notice)

Options:
* “Mechanical Turk”. Wait at the peephole and push the bucket over yourself
* Switch mechanisms and pressure sensors, doorbells.
* Motion Sensor (Passive Infrared, most outdoor motion lights use this)
* Laser trip wires. Catherine Zeta Jones style.
* Blue Tooth low energy or wifi sensing using triangulation from the target’s device
* Computer Vision. Put up a webcam and have a program actively monitor the spot

Mechanical Turk

Requires Human Intervention

Minimises mechanical failures, using dynamic (human) component

You get to see the booger storm in real time

Low part count

Switch Mechanisms

Mechanical Part, can be failure prone.

Easy to build, use, and comprehend.

Cheap, and accessible components

Passive Infrared

Raw data is often failure prone, catches animals, other non-target changes.

Hard to calibrate, largely guess-work

Minimises mechanical failures, using passive, static component

Easy to use, and comprehend.

Cheap and accessible components

Laser trip wires

Difficult to calibrate

Difficult to source and find information
More expensive, and more parts
With proper installation, fairly static component

Effectively determine location.

RF Triangulation

Requires advanced programming techniques
More expensive parts
Effectively determine location.

Computer Vision

Requires advanced programming techniques
More expensive parts
Effectively determine location.

You get to see the booger storm in real time

Speakers

You can evaluate speakers in many ways. We’re probably not going for “quality” here.

When you’re evaluating sound for your installation consider the following.

• How loud do they need to be?
  
  • How much power and amplification are required to drive them to that volume?
  • How will they be powered? Batteries? Passively?
• Where will they be?
  
  • Do they need waterproof enclosures?
  • Will either side be exposed?

For most things you’re probably ok to pick some speakers out of the garbage or second hand store and power them with an off the shelf amplifier.
That’s what we’ll do here. I tend to use This Pyle Amplifier for most low power applications. It’s a good “set it and forget it” piece.
My only problem with it is that it can not be remotely power cycled without modification.

Controller

I’m not going to cover the controller choice here. I typically use one of the following.

• Arduino-alike (Arduino, Teensy, Particle Core/Photon, etc)
• Single Board Computer (Raspberry Pi, Beagle Bone)
• Computer (Intel NUC, or whatever happens to be around)

You could make any of them work for you for this purpose.

Booger Storm Mechanism

For the purposes of this series I needed a conceit that required a mechanical component. I chose a booger trap. Boogers are probably hard to source, if you were going to make this a long term operation, I’d probably suggest you use the contents of your garbage disposal and compost and some pumping mechanisms.

So, questions to ponder.

• What quantity (mass and volume) of boogers are required before it’s a storm?
• Do they need to blow around?
• What’s the viscosity? Will they fly or spill out of the container?

Possible Solutions
* Bucket of boogers and a pulley/motor mechanism
* Dry pile of boogers and a fan
* Idea: Second fan with water or a humidifier to to reconstitute snot

Bucket of boogers

Custom Made Mechanism.
More and more expensive parts
Feels like something out of a cartoon.

Works at higher viscosities and densities.

Booger Fan

Limits viscosity and density of substrate
Conspicuous
Cheap off the shelf parts.

Easy build

Bringing it together.

We’re going to use a fan and a camera, and a mac. This is a one-day installation, so we’ll use prefabricated cables and zip ties instead of custom cabling and conduit. We’re going to wing mounting and calibrating the camera. so here’s our rough plan:

We’ll trigger the fan with a Belkin Wemo so we don’t have to mess with 120v power. I don’t like them for long term installations as they have some network issues, but it should work great for today.

An intel nuc will watch and record the camera, and do the image processing, and play the audible siren.

This plan requires no custom connectors, cables or parts. It’s easy to implement and the best part is that I’ve got everything on hand.

22nd January 2016