Poor Mad Science

I am not just a mad scientist, I’m a poor mad scientist. Here you’ll find my mad science experiments and doodads that I performed or created at home and on the cheap. I’m a big proponent of inexpensive, open-source science, and here is where I show my support with my own at-home dabbling.

Homemade Infrared Goggles

For about $10, you can build your own infrared goggles. No, these goggles won’t let you see through houses, clothing, or in the dark. These goggles work simply by blocking all light that is not infrared. In technical terms, the goggles are infrared-pass goggles, meaning they filter out everything that is not infrared.

The inspiration and design of these IR goggles comes from Bill Beaty.

Warning: Wearing these goggles causes dilation of your pupils, which means more infrared light is entering your eyes than normal. I can’t tell you whether or not this is dangerous.

The first thing you do is purchase a cheap pair of welding goggles with replaceable filters. I got these ones on Amazon, and they work great. You’ll also need a sheet of 181 Congo Blue gel filter and a sheet of 106 Primary Red gel filter.

Welding goggles

Welding goggles

Take the colored filters out of the welding goggles and for each eye, add 1 red filter and 1-6 blue filters. Put the goggles on on a bright sunny day, and enjoy walking through a surreal world of infrared light.

Red and Blue gel filters

Red and Blue gel filters

Most infrared light is invisible to the human eye. These goggles do not allow you to see more infrared light than you normally can–they just block everything else so that all you see is the infrared light. To “see” infrared light that is invisible to the human eye, try this IR detector. The way these goggles work is that the red filter blocks the various shades of blue light and the blue filter blocks the various shades of red light. Together, they block almost all shades of visible light except infrared and the very near-infrared.

The picture below is sort of what it looks like to walk the sunny outdoors while wearing the infrared goggles. The reality (looking through human eyes instead of the eyes of a camera) looks even more surreal. The purple/violet colors are a lot more powerful and vibrant than what you see through the eyes of a camera.

It looks even cooler through human eyes!

It looks even cooler through human eyes!

Warning: Do not look directly at the sun with these goggles. Even though the sun looks a lot dimmer, the goggles are not blocking any of the visible or invisible infrared light, which can severely damage your eyes in seconds.

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How to use your Video Camera as an Infrared Detector

Many modern video cameras have a “night” mode, which allows grayish video of close subjects to be taken, even in utter darkness. This feature means that such video cameras can be used as infrared (IR) detectors–they can pick up infrared light that is invisible to the human eye.

The video camera I’m using today is a Sony DCR-SR45. It’s not a high end camera, and I purchased it used, but it has “Nightshot Plus,” which I’m interested in today.

Here’s how the night mode works on these cameras:

1) An infrared light on the front of the camera illuminates the subject with infrared light. You might see the near-infrared output of this light as a faint red glow if you look directly at the video camera when it’s in night mode.

Infrared light source on video camera

2) The infrared sensor in the camera picks up on the reflected IR light to render the picture. If you’ve ever used such a camera, then you know the video it produces when you’re using night mode is grayed out and looks something like the following:

Nightshot Mode

So what can we do with this IR detector? Well, one of the easiest things we can do is check if our TV remotes are working. Most TV remotes work by broadcasting an IR signal to the TV. To the naked eye, this IR light is completely invisible, but not to our IR detector. Check out the side-by-side video captures of a TV remote without and with night mode:

IR remote through video camera with nightshot

If you want to try it for yourself, just point the TV remote at your video camera (which should be in night mode) and press a button on the remote. If you’re watching the screen on the video camera, you should see the little bulb on the tip of the remote turn into a rapidly flashing light.

To the naked eye, the infrared light from the TV remote should be completely invisible, but even video cameras without night mode may detect some infrared light (see the left picture above). Turn it into night mode, however, and the IR emission from the remote becomes practically blinding.

Another interesting use for your IR detector is to tell from a distance whether a heat source is radiating thermal energy in the form of IR radiation. Recall from physics class that heat is transferred three ways: conduction, convection, and radiation. If you run really hot water through a faucet and take a look at it through a video camera on night mode, you won’t notice anything unusual. This is because the hot water isn’t transferring much heat through IR radiation. If you hold your hand close to the stream of hot water you won’t feel much. Touch it, however, and the heat from the water is conducted into your hand. Now take a look at a radiative heater through your IR detector, and you’ll see something interesting. In regular video, the heat source in the heater appears orange but it’s well-defined. Turn on night mode, and the heat source turns into a bright diffuse glow. It’s particularly interesting, to watch such a heater warm up through a video in night mode. When the heating tubes (or coils) are cold they look well defined (but monochrome) in the video. As they heat up, they become enveloped in a diffuse, white glow.

Visible-IR Comparison of Radiative Heater

If you’re the nefarious type, you may find our IR detector very useful. Security cameras with nightvision capabilities usually illuminate their field of view with infrared LEDs. To the naked eye, this illumination is invisible, but point a video camera with night mode toward a house with nightvision security cameras, and those security cameras stand out like spotlights.

One thing I haven’t tried yet is to point the video camera in night mode toward a circling police helicopter to see if they’re using an infrared spotlight to illuminate the ground. Some day I’ll check it out. I’ve always been curious whether or not our local police chopper uses IR technology to track suspects.

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Simple Homemade Spectroscopy

I love chemistry. I get to play with fancy instruments, do some experimenting, and act all sciencey and stuff. Next week, for example, I get to play with a nice spectrometer and do some mathjitsu on spectral stuff. Anyway, I decided to see if I could build a simple spectrometer myself. Five minutes later I learned how to build a simple device out of cardboard, some tape, and a DVD. An hour later, and here’s my spectrometer:

Homemade Spectrometer

Homemade Spectrometer

This spectrometer was designed by PublicLab.org–a nonprofit community science organization. The kit for the spectrometer can be purchased on Amazon, but I built mine from schematics provided by PublicLab.org.

It’s really an amazing spectrometer for its simplicity. Light enters a tiny horizontal slit at the front of the box and passes through a diffraction grating made from a piece of a DVD. Essentially, the light coming through the narrow slit hits the DVD which splits the light into the wavelengths that compose it. What you see looking through the DVD lens is the line spectrum of the light source. A good explanation of the tech and the underlying science can be found here.

So let’s take a look at a few emission spectra (Note: Usually you see spectra oriented horizontally, but these are oriented vertically… same thing different perspective):

Spectrum of sunlight through clouds

Spectrum of sunlight through clouds

Spectrum of Fluorescent Lightbulb

Spectrum of fluorescent light bulb

Spectrum of Incandescent Lightbulb

Spectrum of Incandescent Light bulb

I got these photos simply by holding the little homemade spectrometer up to my phone camera. I have a rather cheap phone camera so the spectra are not as well defined in the images as they are if I look through the spectrometer with eyes only. The really neat thing is that I can upload these images to SpectralWorkbench.org where my spectra are converted into graphs. After calibrating my spectroscope with a fluorescent light, I can compare my spectra against each other and against spectra taken by others. It should be a very useful tool for home spectroscopy.

In the image below, I’m comparing the spectrograph of a white L.E.D. light (white line and color spectrum) with the spectrograph of the same light shining through dark green glass (red line). From this comparison we can deduce the absorption spectrum of the green glass. It shows that the green glass reduces the intensity of the light across the spectrum (i.e. the red line is lower), and it shows that the glass absorbs blue and violet from the L.E.D. (i.e. red line drops at the left side).

Perhaps the most interesting spectrum I saw was that of sodium in the flame of a butane lighter. First I made a sodium chloride solution by stirring ordinary table salt into hot water. Then I dipped a cotton swab into the solution, held it over the flame of a butane lighter, and watched it through my spectroscope. At first all I saw was the full spectrum of the burning butane, but all of a sudden a yellow line much brighter than the rest of the spectrum appeared. The yellow line was the spectral signature of sodium. I’ve done this experiment in chemistry lab, but to see the same results at home with a homemade spectrometer is magical.

Getting the spectrograph of a fluorescent light.

Getting the spectrograph of a fluorescent light.

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