In this section, you will learn how to protect yourself and your projects from injury or damage as you work with electricity and electronics.

You will understand why electricity can be dangerous to humans, identify ways to avoid electrical damage, and describe methods to keep you, your workspace, and your project safe.

You may be asking yourself, "Just how is electricity dangerous?"

To answer this question, we need to understand two aspects of electricity: the “pressure” pushing it through a wire, measured as voltage, and the amount of electricity that's being pushed through that wire, measured as amperage.

For you to get an electrical shock, you have to touch an exposed wire that has electrons being pushed through it by some force, measured in volts. Higher pressure is measured as higher voltage.

Your skin does a great job of protecting you from this pressure (voltage)—but only up to a point. Once you cross a certain threshold—about 50 volts—the electrons can begin to penetrate your skin. That number gets lower if your skin is wet, and a lot lower if your skin is broken or cut. When this happens, you start to feel the painful sensation of an electric shock.

Now it gets dangerous because it’s not the voltage that kills you—it’s the amount of electricity flowing through your body (measured in amps) once the voltage opens the door. Even moderately high currents—as little as one amp—can burn you or stop your heart. How much current can flow from a wall outlet? Fifteen or twenty amps—and 120 volts can penetrate your dry skin.

That’s why we have created a safe learning environment that has low-voltage/low-current devices so you can experiment to your heart’s content without hurting yourself or someone else.

You can still damage the electronic components you’ll use in this class, and even your computer under some circumstances, if you’re not careful. But it's very unlikely that you'll hurt yourself if you follow our precautions.

So please pay close attention to this section; review safety practices often; and whatever you do, DON’T experiment with anything directly powered by a wall outlet. Always power your projects with a battery or a low-voltage transformer.

As you know by now, power from a wall outlet can be very dangerous!

In these courses, we will never use wall outlets directly for power. When we do plug into the wall, we use transformers that convert high-voltage alternating current into the low-voltage direct current that your components are designed for, at a level that is safe for you.

You still need to be careful and pay close attention to the details. Even with low-voltage current, you can burn up the electronic components in your kit before you know what went wrong.

Keeping you and your workspace safe is the top priority. Review the following guidelines to ensure your safety while you have fun with your breadboard:

While most of the components you use are not too expensive, some are. As you advance in your work with electronics, components can become very expensive—hundreds of dollars each. Microcontrollers start at about $7 and can cost $100 or more. Even on the low end, if you fry several microcontrollers in a row, we may have to ask you to take out a loan to chip in for that.

Frying an electronic component (letting the magic smoke out of it) is almost always a sad thing. How does it happen? There are several ways:

Some electronic components that use direct current are sensitive to the direction of the flow of electricity through them. They will only work with the electricity going in one direction. In extreme cases, they will die if the current is reversed. We say that these components have polarity.

LEDs are a good example of a component with polarity. If you plug an LED into the breadboard backward, it will not light up. You might think it has burned out without realizing that it was just installed backward. The LED will not die; it just will not light up. So how can you tell which way to plug in an LED? Look closely at a new LED where the legs (called "leads") have not been bent and are still parallel. One lead is longer than the other.

That is not an accident. The longer leg is the POSITIVE lead; that wire always needs to be inserted into the breadboard TOWARDS THE DIRECTION THAT POWER IS COMING FROM. In a circuit by itself, we would connect the long lead to the red wire and the short lead to the black wire.

A key concept in working with electricity is knowing how to keep it “in bounds.” Most materials fall into one of two categories: they either conduct electricity or they don’t. If they do, we call them conductors; if they don’t, we call them insulators. Conductors are almost always wrapped in insulators to keep the electricity from leaking out to anything that could be damaged—like you.

Then, making sure that there is good insulation everywhere it needs to be is a key strategy in keeping you and your electronic components safe. Click each topic below to review the following safety guidelines!

Finally, let’s circle back to lithium-ion batteries, which are another potential fire hazard just by themselves. The hazard occurs when the material in the battery becomes extremely hot and causes a fire and/or an explosion. This usually happens in one of two ways:

Lithium-ion battery fires are extremely dangerous because they can start by exploding, which sends shrapnel and burning chemicals everywhere—like into your eyes—and once started, they are hard to put out. Sometimes they have to burn themselves out. If the battery is close to you or in your pocket, that can be very bad.

Houses and cars have caught fire and people have been severely burned. Quality batteries have safety mechanisms – such as temperature monitoring – built into them to help prevent problems. If you buy batteries, look for these features.

Bottom line: Don't charge batteries unattended. Pay very close attention to polarity. Watch this video to see how a battery can easily explode:

• Recall why electricity can be dangerous to humans
• Identify ways to avoid electrical and battery damage
• Describe methods to keep you, your workspace, and your project safe

Much of the information you have covered in this section considers circuits far more dangerous and powerful than what you will interact with - however, it is still important to have a broad understanding of electrical safety, as it will apply to the work you do with your robotic arm just the same.