June 9, 2013

Mr Freeze Part 3: The Goggles

These were a bit tricky.  After much testing, prototyping, and tweaking, I happily ended up with this terrifying creation:

In person, they look excellent - a textured, glowing lens with 6 hotspots of light around a black pupil-like-darkness set into welding goggles.  Also, I can see surprisingly well through a tiny hole in the center of each lens.  It's super bright in the photo because you are seeing 12 LEDs going at full blast, but in person it looks great in a bright room.  So how did I do this?  Lets go.

The Process

I started with a pair of cheap welding goggles, chosen both because they were a form I liked and also because welding goggles have easily removable lenses so you can switch the darkness rating for different kinds of welding.  In this picture you can see a lens cap ring unscrewed from the goggles body, the dark lens, clear lens, and plastic gasket ring removed.

Putting in the lights, I needed to find a way to have tons of light come out of the lens with absolutely none coming into my eye.  The easiest way was to mount the LEDs to a mirrored Acrylic disc.  Simply gluing tinfoil to the acrylic would have done, but I already had some with a mirrored film attached.  Before we go much further, let's look at a cross section plan of this thing:

Don't be scared - it's actually pretty simple.  Now this is what I ended up with - far, far away from where I started.  Here's an explanation of the pieces of the cross-section from the front to the back.  Pictures follow.
  • The lens holder is an original part of the goggles, basically a ring that screws onto body to hold onto the various lenses.
  • The glass lens is a flat, boring glass disc that came with the goggles.  I kept it to make sure the front of each lens has a uniform, shiny surface.
  • The gasket is just a tiny plastic ring that acts as a small spacer between the glass and plastic.
  • The plastic disc is a disc of opaque, white plastic I cut from an Ikea storage box.  The front is lightly textured and the back has a regular triangular tessellation carved into it with a dremel.  Through the center is a small hole (roughly 1.5cm diameter) through which I can see.
  • The black foam tube is a small tube I cut/carved from EVA foam (craft foam) to keep the LED light from making it into my eye by maintaining a solid tube of darkness.  The squishiness of the foam also helps keep everything in place.
  • Six LEDs are mounted evenly around the foam tube, mounted onto a piece of mirrored acrylic simply by pulling the leads through tiny holed drilled through the acrylic.  Acrylic because it's solid and can be clear in the center, mirrored to bounce all the possible light out of the front of the lens.  The mirroring was a film applied to the front side, but tinfoil or aluminium tape would work equally well.  I made sure to cut away the mirroring in the center of the acrylic so I could see through.
  • The foam disc is for comfort, to protect my face from the electronics, and to make sure to block any light that comes through or around the acrylic.

In Pictures

Here you see the LEDs wired in parallel into the mirrored acrylic.  I used the leads from the LEDs and resistors themselves to complete the circuits around the center for the positive sides of the LEDs and extended with small wires around the edges for the negative side.

Here you see both acrylic/LED discs mounted into the goggles.

Here are all the layers in front of the LEDs, though not quite in the right order.  You can see the pattern etched into the back of the plastic disc in this picture.  When all lit up, that pattern shines through each lens, though the front of each plastic piece is flat.  It's a cool effect.

After some testing, I wired the left lens into the right, thus putting all 12 LEDs in parallel.  Then I could replace the noseguard with a new one made from bent steel wire and EVA foam and add the foam discs.

All put together.

And that's it for this week!  Right now the voltage source is a pair of AA batteries (totaling 3V).  All LED/resistor calculations were simplified by using this website, LED Wizard.  They're not hard calculations, but if you're new at any kind of electronics, it's nice to have a computer tell you that you're on the right track.

Future modifications will be few.  Namely, I'll change the wire-hanging-from-my-goggles look to one that looks like a curlicue earpiece wire attached to a fake (or potentially functional) earpiece.  Also, I'm going to change the voltage source from simple batteries to an arduino so I can add dimming for picture taking (via a dimmer knob hidden on the chest armour) and timed pulsing.

See you next time!

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