LEDs and Lighting Class
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Introduction: Electronics Crash Course

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In order to make things light up, we need to have a basic understanding of electricity, and the tools required to work with it. In other words, we need to cover the basic of electronics; the art of regulating the flow of electricity. By controlling the flow of electricity in different ways, we can work with the different light sources to achieve all kinds of lighting effects. However, before we can do that, it is important to review the fundamentals. This is a little bit difficult at times, but please stick with me.


A charge is the build up of charged electrons.

Ground is an area that neutralizes that charge by removing excess charge.

For instance, charged electrons build up in a thundercloud. When it reaches a certain threshold of charge, the electricity is able to ionize the air and arc across the sky as a plasma. Albeit it could travel in any direction, it goes towards the Earth because of its large difference in charge. Just like the north and south poles of a magnet attract, so do negative and positive charges.

However, unlike magnets which, keep their charge when they meet, electrical charge functions differently. When the (typically) negative charge from the cloud strikes the much larger positively charged surface of the Earth, the Earth is able to absorb and dissipate the negatively charged particles from the thunder cloud. This is what is meant by electric ground neutralizing the charge. The same thing that happens during a storm also happens on a much smaller scale with all electronics.


AC / DC

When we are talking about AC/DC, we are not talking about the Australian hard rock band, but the two different types of electrical current.


There is alternating current or AC. It is called alternating current because the electrical signal alternates above and below the electrical ground. So, if you were to look at the picture of the 12V AC waveform above you will notice that it alternates above and below the electrical ground (indicated by the little yellow marker on the left). This type of waveform consists of a current that is constantly fluctuating between a positive and a negative voltage.

AC electricity is the type of current you will find coming out of your home wall socket.


The other type of current is direct current or DC. It is so named because it travels in a direct line above ground. If you will look at the waveform of a 12V DC voltage supply, you will notice that it's basically a solid yellow line running parallel above the ground. This type of electricity consists of a steady positive voltage, set apart from a ground plane.

DC electricity is the type of current that comes from batteries, which are basically special containers that store a predetermined amount of voltage.

AC wall current can also be rectified (more on this later) to become DC voltage. Just because a device plugs into the wall does not necessarily make it an AC device. If you look carefully at a power adapter, it will tell you what the output is. Aside from voltage and current, if you look carefully at the bottom of the label, you will see an illustration that even tells you the inside of the plug is a positive DC voltage and the outer barrel is ground.


Ohm's Law

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Imagine a ball being thrown through the air.

Voltage is the speed the ball is traveling. This is measured in Volts. It's symbol is a capital V.

Current is the size of the ball being thrown. This is measured in Amperes (or Amps for short). Its symbol is a capital A.

Before I dive into ohm's law, let's revisit our ball analogy. If you have a small ball traveling at a very high speed, it could potentially have as much or more power as a large ball traveling at a very low speed. In this way, you could say there is a direct relationship between the speed a ball is traveling, the size of the ball, and the potential power of the ball.

Of course though, we are actually not really talking about balls, but electricity. When dealing with electricity, voltage and current are in a direct relationship with power. In a circuit, power is expressed in terms of Watts. The symbol for this is a W.

You likely have heard the term Watts before in relation to light bulbs. All light bulbs are measured in the amount of power they consume.

If we know how many watts a light bulb can consume, and that it is receiving 120 volts from a wall outlet, we can then deduce how much current it will require. By dividing 60W by 120V, we are left with the value of 0.5 amps of power. On account of this relationship between the three, given any two values, we can solve for the third.

There is also another factor we have yet to talk about that also plays a role, and that is resistance. In our analogy, resistance is the headwind that the ball must fight against to move forwards. On a calm day, there might be little resistance to it's flight, but on a windy day, it might have to fight against the wind pretty hard. Again, we are actually talking about electrical resistance in a circuit and not throwing a ball.

Resistance pushes against the flow of electricity. As such, it is also in direct relationship with Watts, Voltage and Current. Resistance is expressed in Ohms (after it's discoverer). This mathematical relationship between Watts, Voltage, Current and Resistance is unsurprisingly called Ohm's Law.

Ohm's Law is not something you must memorize, but it will play an important role later when determining how much resistance a circuit must have. Thanks to this law, a circuit having a minimum amount of resistance is not optional, but necessary. The energy in the circuit must encounter resistance in order to expend itself. The thing in the circuit which uses energy is considered the Load. If an electrical supply is connected to ground without a load to use up the energy, bad things will happen.


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When building a circuit, there are basically two ways in which you can connect a load. They can either be in series or parallel.

When you wire electrical components in series, they are in a line.

So, if you were to break the circuit in any way -- say by unplugging a light bulb -- electricity has no path to continue flowing and the whole connection is broken.

Alternately, you can prevent this problem by wiring the light bulbs in parallel. When wired in this way, they are connected side-by-side and share the same electrical connections on both ends.

Thus, when you unplug one bulb, electricity can continuing flowing through the other one unfettered.


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Power supplies such as batteries can also can be connected in series and parallel. However, before we get to that, let us take a moment and talk a bit more about batteries.

The most common types of batteries you will encounter are standard cylindrical dry cell batteries. Most notably these consist of AAA, AA, C, and D batteries. What is important to know about these batteries, is that even though they are different sizes, they are all rated at 1.5V (remember - V is the abbreviation for volts).

What changes as they get bigger in size is the amount of power they are capable of producing. A D battery will be able to provide power for much longer than a AAA battery. In other words, a bigger battery can provide more amperes for a longer amount of time than a smaller battery.

Batteries are measured in Amp Hours or Ah. This is basically the measure of how many amperes can be drawn from the battery in an hour. For instance, a 20Ah battery will let you draw 1 ampere for 20 hours. However, let's say you are building a giant robot and it needs 5 amperes per hour; in this case you can run that robot for about 4 hours using the same battery until it runs out (20Ah / 5A = 4 hours).

It may have by now dawned upon you that 1.5V is not very much. You might be wondering why we don't just use a 9V battery instead? Assuredly a 9V battery is producing more power than a 1.5V battery.

This, in fact, is not true at all. 9V batteries actually are not great in producing power at all. A good way to think of a 9V battery is to imagine 6 really small 1.5V batteries smushed together inside. In fact, if you take a 9V apart, that is essentially what you will find inside. Now, compare that to the size of 6 AA batteries for instance. The 9V batteries are rather tiny by comparison!

The only time 9V batteries come in handy is when you need a relatively high voltage for a project that doesn't require a lot of current and it needs to fit it into a small enclosure.

Well then, you may be wondering how you can power anything if batteries are only 1.5V? The answer is rather simple. We connect them in series.What this means is that we connect them front-to back in a row. So the positive (plus) end of one battery gets connected to the ground (minus) end of the next battery, and so on, and so forth. We can then calculate the new voltage simply by adding 1.5V for each battery in the series. So, if you have three 1.5V batteries in series you could multiply 1.5V times three to get a total of 4.5V.

The easiest way to connect batteries in series is to use a battery holder. To calculate the voltage that a battery holder provides, you simply need to count the number of batteries it holds and multiply it by 1.5V, just as you would with any other set of batteries connected in series. So, a 4-cell battery holder would produce 6V of power (1.5V x 4 = 6V).

To access the power provided, simply connect the red wire to the positive terminal on your project, and the black wire to ground. As a reminder from earlier, red wires always indicate a positive voltage, and black always indicate ground.

We can also connect batteries side-by-side in parallel so long as they have identical voltage ratings. When power sources are connected in parallel, the voltage remains the same, but the amount of available current increases. This is useful when a single battery does not provide enough current to power your circuit.

Keep in mind, this will only work if the batteries are the exact same voltage and should be avoided if possible. Without the proper diode protection circuit, fluctuation in voltage between the batteries will force them to try to charge one another, decreasing their lifespan.


Circuits

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A circuit is a complete loop in which electricity can flow. An ideal circuit is any path in which electricity can flow from start to finish and pass through a Load, where the energy is put to use. This Load can be almost anything that uses the power, such as a light bulb, LED, or EL wire.

Circuits for lights are usually fairly simple. A power supply is connected to both terminals on a light source, and then electricity is allowed to flow through it, which completes the circuit and turns the light on.

That is the most fundamental circuit that can be made.

Of course more complex circuits can be made. Multiple lights can be wired together in series and/or parallel, or a switch can be placed in series to turn lights on and off. Additional components can also be added. For instance, when dealing with LEDs, we will also include a component called a resistor in series with the LED. However, more on that in a bit.


Soldering

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To make lighting circuits, sooner or later you will need to know how to solder. So, there is no sense dancing around the subject. Let's get down to business.


Holding the Iron

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A soldering iron is held like a pencil, but with one significant difference. Instead of holding it by the tip, you hold the soldering iron further back by the insulated handle.

That's all there is to that.


Never touch the metal part of the soldering iron while it is turned on. This can result in nasty burns, and is generally unpleasant.

Never leave soldering iron resting on the table. It will burn your work surface and could potentially start a fire.

Soldering can build up a mighty appetite, but don't eat while soldering. Some solder has lead in it, a known carcinogen. Even lead free solder has things in it you likely do not want to ingest. Before chowing down on a slice of pizza, turn off the soldering iron, take a break, and wash your hands with soap and water.

Breathing in the fumes from soldering is bad for you. Always use some sort of ventilation fan to minimize your exposure. Your lungs will thank you.

While arguably not necessary, it is recommended that you wear safety glasses while soldering. Solder has been known to splash and splatter. Albeit a rare occurrence, getting burning hot solder in your eye can be an unpleasant experience (or bits of cut wire, for that matter).

After soldering, you will always want to remember to wash your hands with soap and water.


Tinning the Iron

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Turn on the soldering iron and wait for it to heat up. If you splurged on an adjustable temperature model, you can dial yours in to about 650 degrees.

Once it is heated up, you will want to tin the tip before using it for the first time.

All this involves is thoroughly melting solder all over the tip of the iron. This makes sure the tip has a nice solder coating, which will make it easier to melt solder the next time you use it.


Cleaning the Iron

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Every time you melt solder using the tip, you will want to clean it off.

To do this, simply drag the tip 2 or 3 times across the cleaning pad.


Solder Wires

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Now is time to solder some wires together.

To do this, strip the insulation off of the ends of two pieces of stranded wire using your wire stripper.

Slide a 1" piece of shrink tube onto one of the wires and then twist the two ends of wire together.

Place the soldering iron against the wire to heat it up, and push the solder into the wire. It should start to melt and get wicked up into the wire, coating it in silver.

Remove the soldering iron to let it cool.

Trim the excess parts of wire so the connection is as compact as possible.

Slide the heat shrink tube over the solder joint.

Shrink it into place with a heat gun.

Congratulations! You have just soldered something together. Continue practicing until the act of soldering feels comfortable.

CLASS PROJECT

Share a photo of your finished project with the class!

Nice work! You've completed the class project