In the last post (here),
we talked in detail about the breadboard and how it works. Now we will be using
the breadboard to explain the concept of connecting components in parallel or
in series. This is also essential because our robot and programming is only as
good as the circuit it. We will also look at these connections in a breadboard
view and in a schematic view. The
schematic is a more
abstract way of showing the relationships between components in a circuit. Schematics
don’t always show where components are placed relative to each other, but they
show how they are connected.
(Schematic View)
(Source: Arduino Projects Book)
Let us quickly glance through the components
in the circuit.
An LED, or light-emitting diode, is a component
that converts electrical energy into light energy. LEDs are polarized
components, which mean they only allow electricity to flow through them in one
direction. The longer leg on the LED is called an anode, it will connect to
power. The shorter leg is a cathode and will connect to ground. When voltage is
applied to the anode of the LED, and the cathode is connected to ground, the
LED emits light.
A resistor is a component
that resists the flow of electrical energy (see the components list for an
explanation on the colored stripes on the side). It converts some of the
electrical energy into heat. If you put a resistor in series with a component like
an LED, the resistor will use up some of the electrical energy and the LED will
receive less energy as a result. This allows you to supply components with the
amount of energy they need. You use a resistor in series with the LED to keep
it from receiving too much voltage. Without the resistor, the LED would be brighter
for a few moments, but quickly burn out.
A switch interrupts the
flow of electricity, breaking the circuit when open. When a switch is closed,
it will complete a circuit. There are many types of switches. The ones in your
kit are called momentary switches,
or pushbuttons, because they are only closed when pressure is applied.
SERIES CONNECTION
You’re going to use the Arduino in this project, but
only as a source of power. When plugged into a USB port or a 9-volt battery, the
Arduino will provide 5 volts between its 5V pin and its ground pin that you can
use. 5V = 5 volts, you’ll see it written this way a lot.
If your Arduino is connected to a battery or computer
via USB, unplug it before building the circuit!
Connect a red wire to the 5V pin on the Arduino, and put
the other end in one of the long bus lines in your breadboard. Connect ground
on the Arduino to the adjacent bus line with a black wire. It’s helpful to keep
your wire color consistent (red for power, black for ground) throughout your
circuit.
Now that you have power on your board, place your switch
across the center of the board. The switch will sit across the center in one
direction. The bend in the legs of the switch point to the center of the board.
Use a resistor e.g. 220-ohm resistor to connect power to
one side of the switch. On the other side of the switch, connect the anode
(long leg) of the LED. With a wire connect the cathode (short leg) of the LED
to ground. When you’re ready, plug the USB cable into the Arduino.
Once everything is set to go, press the button. You
should see the LED light up. Congratulations, you just made a circuit! This is
similar to the circuit in the video explaining how a breadboard works with the
exception of the added push-button for control. Here, the push-button lies in line with the resistor and the LED i.e there is only one current flow path and so
we say it’s in series with the resistor and LED. Looking at the schematic view
of the circuit explains this easier. Once you’re tired of pressing the
button to turn the light on, it’s time to shake things up by adding a second
button.
COMPONENTS IN SERIES COME ONE AFTER ANOTHER
Once you’ve removed your power source add a switch next to the one already on your breadboard. Wire them
together in series as shown below. Connect the anode (long leg)
up the LED to the second switch. Connect the LED cathode to
ground. Power up the Arduino again: now to turn on the LED, you
need to press both switches. Since these are in series, they
both need to be closed for the circuit to be completed.
The two switches are in series. This means that the
same electrical current flows through both of them, so that they both have to
be pressed for the LED to light up.
PARALLEL CONNECTION
COMPONENTS IN PARALLEL RUN SIDE BY SIDE
Now that you’ve mastered the art of things in series,
it’s time to wire up switches in parallel. Keep the switches and
LED where they are, but remove the connection between the
two switches. Wire both switches to the resistor. Attach the
other end of both switches to the LED, as shown in Fig. 12.
Now when you press either button, the circuit is completed and
the light turns on.
These two switches are in parallel. This means that
the electrical current is split between them. If either switch is pressed, the
LED will light up. With Parallel connection, there is more than one path for current flow and the components do not lie in line, rather they run side by side having separate paths.
We have looked at connecting components in series and parallel, we used push buttons mainly to illustrate this, but it is important to note that any type of component can be connected using these ways depending on the design of the circuit. We can have batteries, resistors, capacitors and the likes in series or parallel. There are even circuits that combine both arrangement. There are some components in series in the circuit while some are in parallel. This begs the question; what are the pro's and con's to each arrangement and why may we want to use one or the other or both.
Series Properties
- It can be easily constructed using less conductor.
- In the series circuit, the same current is flowing through each component or load IT=I1=I2=I3
- Each component has resistance that causes a drop in voltage (reduction in voltage). VT = V1 + V2 + V3…
- Total resistance goes UP with each resistor since the current has must go through each resistor. Req = R1+R2+ R3
- If a single component is damaged, the current does not flow through the circuit and the whole
- series will become useless.
- In a series connection, fault cannot easily detect.
Parallel Properties
- The construction of the parallel circuit is complicated. It requires more conductor
- In the parallel circuit, the equivalent current is the sum of current passes through all the branches. IT = I1+ I2 + …
- In the parallel connection, each branch has the same voltage. VT = V1 = V2 = V3…
- The more paths, the less TOTAL resistance. 1/ Req=1/R1+1/R2+1/R3
- If any of the components are damaged, the current will not flow through that particular branch as current flows
- through other parallel branches, this circuit will work properly.
- You can easily find out the fault condition and disconnect from the connection.
Eventually, it depends on what we want to achieve, if we want simplicity or just to oppose the
flow of current, we may connect resistors in series to achieve this. But if we need voltage to
be stable in parts of the circuit or we need more redundant paths, we may connect in parallel.
This looks like a lot but I endeavor you to relax and go over it as many times as you desire
because these are the building blocks of electronics and robotics and we will be using these
skills as we proceed. You can also try your hands on building different series and parallel
circuits by yourself. Ciao
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