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<config src="./settings.json"/>
<report margin="1in">
<section title="Background">
Before we begin soldering, let's briefly cover some basic electronic components.
<section title="Resistors">
The simplest electronic component is the resistor; they get their name because they resist
the flow of current. If you imagine electricity as water, the resistor is a pipe of some diameter.
The smaller the diameter of the pipe, the less current that will flow. A resistor with a high resistance will act like
a narrow pipe. Each resistor is rated for a value measured in Ohms ($\Omega$) and they typically range from 1-1$M\Omega$.
<figure src="img/resistor.png" caption="Credit: Forrest M. Mims"/>
A resistor can be seen here, notice the color bands on the body of the resistor. These are used
to indicate the resistance value of the part.
<figure src="img/resistorirl.jpg" caption="A Resistor" size="0.3\textwidth"/>
To find out the value based on the color code, the table below is helpful. The colors are
mapped to numeric values based on a modified rainbow (Black-Brown-ROYGBIV-White). The value is analogous
to scientific notation. For a 4 band resistor the first two bands represent the ``a'' in $a\times10^{b}$, the third
band represents the ``b''. Finally, the fourth band represents the tolerance of the resistor (how accurate the resistance
is to its rated value). For some applications, there can be a very narrow tolerance for the circuit to work correctly. There are also
online resistor code calculators that speed things up greatly.
<figure src="img/codes.png" caption="Credit: Forrest M. Mims"/>
</section>
<section title="Capacitors">
The next component is the capacitor, it is essentially a storage tank for electricity. In the water model it would
act like a water tank, where it takes time for the tank to fill and drain. The time to fill the tank is dependent on the rate of the flow (current) as
well as the size of the tank. Capacitors have a ``capacitance'' value that represents the size of the ``tank'' and it is measured in Farads (F). Typically, this
value is small. For hobbyist electronics, values are around $10^{-6}F$ which is typically denoted by the Greek letter mu, as in $\mu F$.
<figure src="img/capacitors.png" caption="Credit: Forrest M. Mims"/>
Below is an image of an Electrolytic Capacitor. Other types of capacitors include ceramic and film. The main difference
in these capacitors is the range that they operate. Electrolytic capacitors typically have a higher capacitance than ceramic, but Electrolytic caps have the
consequence of being \textit{polarized}. A polarized component is one that has a positive and negative lead. If the capacitor is connected backwards and there
is significant voltage it can cause the component to fail, and possible burst. The capacitor will have the polarity indicated on the side. Usually negative lead is labeled,
additionally, the positive lead will the longer of the two.
<figure src="img/capirl.jpg" caption="An Electrolytic Capacitor" size="0.3\textwidth"/>
By combining a resistor and a capacitor an RC circuit is made. The resistor limits the current into the capacitor which decreases
the rate is charges by, and therefore creates a delay in voltage. The image below shows the graph of this occurrence. By selecting specific resistor and capacitor
values the delay time can be set.
<figure src="img/capcharge.png" caption="Credit: Forrest M. Mims"/>
The circuit we will be building relies on an RC circuit to blink LEDs. Essentially it charges the capacitor through one resistor, and once the voltage
reaches an upper threshold, it will drain the capacitor through another resistor. Once it drains to a lower threshold it will start over again. This creates
an oscillation where the on-time and off-time are set by the two resistors. The chip that we will be using is the 555 Timer IC, which handles the logic
of turing on and off the flow of electricity to the capacitor.
</section>
<section title="Additional Components">
In addition to the basic components here are the other components that will be used
<figure src="img/LED.jpg" caption="A 5mm LED" size="0.3\textwidth"/>
<figure src="img/555.jpg" caption="A 555 Timer IC (Integrated Circuit)" size="0.3\textwidth"/>
<figure src="img/IC_Socket.jpg" caption="An IC Socket" size="0.3\textwidth"/>
</section>
</section>
<section title="Soldering">
Here are all the required parts for the workshop,
<list>
<item/>9V battery snap
<item/>Printed Circuit Board
<item/>$10\mu F$ Electrolytic Capacitor
<item/>555 Timer IC
<item/>Two LEDs of any color
<item/>$1k\Omega$ resistor
<item/>$10k\Omega$ resistor
<item/>2 $620\Omega$ resistor
<item/>8 pin IC socket(not pictured)
</list>
<figure src="img/0002.jpg" caption="Required Items"/>
Additionally, A Soldering Iron, Solder, and a possibly a circuit board vice (to hold the board) are required.
<figure src="img/0004.jpg" caption="Tools"/>
<figure src="img/circuit.png" caption="Circuit Schematic for the kit"/>
<list>
<item/>
<list>
<item/>
Typically, the best order to place components is in the order of shortest to tallest. We will start with the resistors. The first two resistor we will place
are the $620\Omega$ resistors (R3, and R4). Before placing the resistors, bend the leads like this:
<figure src="img/0008.jpg" caption="Resistor After Bending"/>
<item/>
Once bent, these will go in the place of R3, and R4. They are inserted into the holes like in the image below.
\textbf{Note:} On this circuit board the holes are a little too close together, making it difficult to position
them flat. For the best results, the resistors
should lay evenly and a flat to the board.
<figure src="img/0005.jpg" caption="R3 and R4 Placed on the Board"/>
<figure src="img/0007.jpg" caption="R3 and R4 Placed on the Board (viewed from the bottom side)"/>
<item/>
It helps to secure the components with a bit of tape to ensure they stay flat to the board while soldering.
<figure src="img/0006.jpg" caption="Tape Added to Secure Components"/>
</list>
<item/>
To begin soldering, the iron should be turned on and allowed to heat. When
ready, apply some solder to the tip of the iron (tinning the iron). Then use the brass
wool or damp sponge on the stand to clean the tip.
<figure src="img/0009.jpg" caption="Applying Solder to the Tip"/>
<figure src="img/0011.jpg" caption="Cleaning the Iron Tip with the brass wool"/>
<item/>
The iron is touched to the resistor's \textit{pad} (the metal ring around the hole).
The solder is then pressed against the pad until it flows onto the joint. Once this happens remove the iron
and allow it to cool before handling the part. Ideally, you should use just enough solder to make an
even cone shape around the wire. The solder should also look shiny, if this is not the case,
it is called a cold solder joint. These tend to be more brittle and can be fixed by reheating the joint.
However, avoid heating anything for too long. The parts on the board, as well as
the circuit board can be damaged by excess heat.
\textbf{Note:} Applying solder directly to the iron isn't an effective way to solder.
Liquid solder gravitates to hotter areas and it will accumulate where the temperature
is at a local maximum. Meaning that the solder wont make it to the pad. Instead apply heat to where you
want the solder to end up.
<figure src="img/0014.jpg" caption="The Desired Wire"/>
<figure src="img/0015.jpg" caption="Applying Heat and Solder"/>
<figure src="img/0015b.jpg" caption="Close Up"/>
<item/>
Next the leads need to be snipped to reduce their length. They can be snipped right where the cone of solder converges to the lead. Be careful, when
snipping these leads, they can go flying through the air. Safety glasses are advised throughout this process.
<figure src="img/0018.jpg" caption="Snipping the Leads"/>
<item/> The next resistors to solder are R1 ($1k\Omega$), and R2($10k\Omega$). The same steps are repeated for these.
<figure src="img/0021.jpg" caption="Inserting R1, and R2"/>
<figure src="img/0022.jpg" caption="Soldering R1, and R2"/>
<figure src="img/0023.jpg" caption="Snipping R1, and R2"/>
<item/>
The integrated circuit can be soldered directly like in the photos, however, it is better practice to use IC sockets. IC sockets
are beneficial, because ICs can easily be removed from the circuit if they are damaged. Additionally, the risk of overheating the IC
while soldering is negated. The IC typically comes from the factory with leads that are not perfectly
90 degrees. To make it fit, the leads need to be pushed together slightly. The IC and its socket will have a notch to indicate
the top of the chip. When placing the IC, ensure that the notch corresponds with the dot on the circuit board.
<figure src="img/0024.jpg" caption="Bending IC Leads"/>
<figure src="img/0025.jpg" caption="Placing the IC with the Notch Aligned with the Dot"/>
<figure src="img/0026.jpg" caption="Placing the IC with the Notch Aligned with the Dot"/>
A method that works well for soldering parts with more than two leads, is to first tack one lead down then put pressure on the part to
flatten it while brefly applying heat to the joint. This allow the part to be placed as straight as possible. Once it is in the desired spot, the
remaining pins can be soldered.
<figure src="img/0029.jpg" caption="One lead being soldered"/>
<figure src="img/0032.jpg" caption="IC being adjusted"/>
<figure src="img/0033.jpg" caption="Remaining pins soldered"/>
<item/> Now capacitor C1 needs to be soldered. Since these capacitors are polarized they need to be inserted in the correct orientation.
On the package for the capacitor, it is labeled with a negative sign to indicate
the negative lead. Also the other lead (the positive lead) is longer. When placing it on the board ensure that the positive lead goes in the hole
labeled with the plus sign. Once the capacitor is in its place, solder it and then snip the leads.
<figure src="img/0035.jpg" caption="Electrolytic Capacitor (note the negative strip and the longer positive lead)"/>
<figure src="img/0040.jpg" caption="Inserting C1 (being careful of polarity)"/>
<figure src="img/0041.jpg" caption="C1 in its Place"/>
<figure src="img/0042.jpg" caption="Soldering C1"/>
<item/>
Next, the LED is soldered. LEDs are also polarized so their orientation matters. The LED will have a flat edge that indicates the negative lead, and the same
longer positive lead. The circuit board has the outline of the LED, align the flat edge of the LED with the flat edge on the outline. Do this for both LEDs then solder them and
snip their leads.
<figure src="img/0043.jpg" caption="LED (note the flat side indicating negative and longer positive lead)"/>
<figure src="img/0045.jpg" caption="Inserting LED (being careful of polarity)"/>
<figure src="img/0046.jpg" caption="Both LEDs in Place (they are oriented opposite from each other)"/>
<figure src="img/0047.jpg" caption="Both LEDs Soldered"/>
<item/> Finally, The 9V battery snap is soldered. Insert the red wire into the hole labeled with the plus sign, and the black to the one
with the negative sign. Solder the wires in, and then snip the leads.
<figure src="img/0048.jpg" caption="Battery Snap Leads in place"/>
<figure src="img/0050.jpg" caption="Battery Snap Soldered"/>
<item/>
Now the kit is finished and can be powered with a 9v battery.
<figure src="img/0052.jpg" caption="Finished Kit"/>
</list>
</section>
</report>