Tag laser

MacGyver Season 2 Episode 12 Science Notes: Jack + Mac

rhettallain 2 Comments

Before I get to this science for this episode (there’s some great MacGyver hacks here), let me say something else about the show. The storyline for this episode was great. It had a nice plot, and I really enjoyed the MacGyver and Jack flashbacks. Now for some science.

Photophone

The best Mac-hacks are real. This is real—very real. It is indeed true that this was an early idea for a phone. Here’s how it works.

  • You need a directed light. One way to do this is to get a mirror that reflects sunlight. A parabolic mirror works a little better, but still the mirror is a great idea.
  • Use your voice to shake this mirror. This changes the intensity of the reflected light to match the wave pattern of your voice.
  • Use some type of electrical photo device (solar panel, photo diode, photo resistor) to modulate an electric current to this same sound pattern from the light. Send this to a speaker.
  • That’s it.

For MacGyver’s build, he uses a microphone and connects it to a porch light. The idea is that the microphone will modulate the brightness of the bulb. For this to work, I think it has to be an LED bulb. An incandescent won’t work (I don’t think) since the hot bulb filament won’t change brightness quickly enough for sound frequencies.

There is also the problem of AC vs. DC. If MacGyver connects to the AC power line going to the bulb, this might not work. But still—it’s very plausible.

On the other end of the photophone, Riley uses a police car light as her transmitter. Again, if this is LED it should work (plus the car runs on DC, not AC). Finally, the only problem is aiming. In practice, you need your detector to pick up the changing brightness from that one light. Of course it’s daytime, so there are many “lights” outside. Putting a lens on the detector to aim it would help a bunch.

OK, now you want to build one of these yourself. You should. It’s actually not too terribly difficult. Let’s start with the simplest part—the receiver. The easiest way to get this to work is to connect a small solar panel to an amplified speaker.

Oh, do you know where I got that solar panel? Yes, it was from a garden light. You put these small lights outside and the solar panel charges a battery during the day and the light comes on at night. They were old and the battery was bad, so I took it apart.

Now for the transmitting side of the photophone. I tried to do this with a laser instead of a light (so that I could aim it). It mostly worked, but it’s a bit more tricky.

This is something I need to rebuild at some point in the future. Make it better. But still, this should be in my list of Top 10 MacGyver Hacks. I need to make that list.

Gum Wrapper and Battery to Start a Fire

Ok, actually this was to melt a wire. MacGyver takes a foil gum wrapper and connects it to two ends of a battery. The idea is that the foil will make a short circuit.

But there are two questions:

  • Is a gum wrapper an electrical conductor? I don’t think they are actually made from aluminum foil—but I suspect that many of these do in fact conduct.
  • Would it get hot? Even with a small battery, yes I think it would.

DIY Non-Contact Voltage Probe

MacGyver needs to find wires behind the wall. He puts together this awesome looking probe (or as Jack calls it—a doohicky)

Actually, this prop is great. Here’s why.

  • It looks cool and it’s clearly a combination of multiple items.
  • It’s not specific—it doesn’t show exactly what MacGyver uses. This is good because that way it could still be plausible.
  • Finally, it’s based on something real.

But how does it work? There are multiple ways to detect voltages without touching—I think the most common method measures a super tiny voltage that is created by nearby electric fields. The NCVP is essentially part of a capacitor. When in the presence of an electric field, there is a voltage across the capacitor and you detect this voltage. I need to build one of these—for fun. I’ve seen a very basic version somewhere.

Kitchen Chemistry to Detect Explosives

How do you detect explosives? MacGyver is correct that most explosives are based on nitrogen. If you measure the nitrogen, you can get an estimate of the type of explosive.

There are many things in the kitchen that can be used to detect chemicals. Here is one that you can do at home—it’s a chemical-based pH detector (to determine if something is acidic). The color of this cabbage juice will change color depending on the pH level of the material.

Here’s how to make it.

Laser-Based Wire Cutter

Here’s the problem. There are two bombs that need to be disarmed at the exact same time.

The idea is to use a laser that turns on two identical cutters at the same time. The first thing to use is a beam splitter. This takes a laser beam and breaks into two beams. I guess that’s fairly obvious from the name. Here is a video showing how that works.

For the cutter part, it uses a photocell as the “switch” to turn it on. Here is a rough diagram I created for this hack.

In the end, these two motors might not cut at the exact same speed. But it’s still a fairly fun MacGyver moment.

MacGyver Season 1 Episode 10 Science Notes: Pliers

rhettallain 2 Comments

Boosting car speed.

Mac and Jack are trying to get away in a car chase (using a not very fast car). Of course MacGyver is going to give them a speed boost, but the first step is to remove the car hood. MacGyver makes some small explosives using chemicals and soda cans. Boom. No more hood.

The second step is to remove the air filter and pour some hydrogen peroxide into the intake. What would this do? This would give the gasoline more oxygen (from the hydrogen peroxide) to produce more combustion. Would this give a speed boost? Probably—at least a little bit.

Chemistry demo – elephant toothpaste.

This is real. Everyone does this—at least all the cool kids do it. You should be cool.

Liquid nitrogen in water

OK, liquid nitrogen is pretty awesome. It’s the same nitrogen that you find in the air, but in liquid form. That makes it very very cold (-196 C). When you add it to room temperature water, the liquid nitrogen boils. In this boiling process it produces a bunch of water vapor—stuff that looks like a cloud.

This was for a different episode, but here is my introduction to liquid nitrogen.

Remote listening device

MacGyver wants to hear what is going on inside a house. The obvious solution is to build a remote listening device. Here’s how it works.

A laser is aimed at a window such that the laser reflects off the window and back to a solar cell. Because people are inside the house speaking, this causes tiny vibrations in the window. The window vibrations vary the intensity of the reflected laser light. When this reflected laser light hits the solar cell, it causes variations in the voltage. Plugging this solar cell into an amplified speaker produces sound. Yes. This is real.

It’s pretty awesome—and you can do something like this yourself. All you need is an amplified speaker and a solar cell (don’t worry about the laser). Connect the solar cell to the audio input and you can hear variations in different light sources.

My favorite trick is to aim a TV remote at the solar cell. You can hear the variations in the IR light that produce different signals to change channels.

Here is a video.

Stop a car with paper

Yup, a version of the banana up the tail pipe from Beverly Hills Cop (great movie). See—everyone is a version of MacGyver at some point.

In this case, MacGyver sticks some paper up the tail pipe of a car. When the exhaust can’t escape, you can’t get internal combustion. Car stops.

Yaghi Antenna

Yes, you can build an antenna out of just about anything—including band instruments. It helps if they conduct electricity. I think this would work.

Technically it’s possible to find the location of a signal with just one antenna (well at least the direction). Just turn the antenna until you get the maximum signal. A better option is to use 2 or more antennas—but you have to work with what you have.

Over inflate tire

Yup. Boom.

Elephant toothpaste version 2

Bigger is better, right? It’s sort of funny.

Fetch with Ruff Ruffman uses a laser to measure temperature?

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I am sorry to point this out, but I can’t help it. My kids watch this show “Fetch with Ruff Ruffman”. It’s mostly an ok kids show. However, there was a problem. In one episode, some kids were in the desert and measuring temperature with (they said it several times and it was even a quiz question at the end) – a LASER. Here is the device they used:

![Images](http://blog.dotphys.net/wp-content/uploads/2008/10/images.jpg)

This is an infrared thermometer with a LASER aiming system. The laser is only there to help you aim. The temperature is determined by measuring the infrared radiation from the object. You don’t even NEED the laser. Those ear thermometers work the same way, but they don’t have lasers.

I guess when a laser is involved, it just makes it so cool that it must be the most important thing. I am going to put a laser pointer on my computer – that way people can say “look, that computer runs on LASERS.”

Fun things to do with a green laser pointer

rhettallain 1 Comment

I went home for lunch today. While waiting, I saw this lizard. We have many lizards in Louisiana, I like them, really I do. So, this is what I did:

No lizards were harmed in the filming of this video.

I was really surprised. I thought for sure that I had tried this before and nothing happened. Maybe it was because of the white surface the lizard was on. Maybe it was because it was an older and wiser lizard (it was larger than normal). Maybe this is already a well known fact about lizards and laser pointers. Needless to say, this was quite entertaining and completely justifies the cost of my laser pointer.