This document summarizes a student project to build an LED flasher circuit using a 555 timer IC. The circuit causes an LED to flash on and off. The students learned that they learn best visually by looking at the circuit diagram. They used problem solving skills to troubleshoot issues like a dim LED. The circuit was also simulated using software. Additionally, the students modified the circuit to make a speaker beep on and off, and added a second LED to alternate flashing.

1. LED Flasher as a Mini System
Leader: Ore Afolayan
Certifier: Kelvin Darden
Abstract
This project will show display the use of a 555 IC and other components such as resistors
and capacitors in a mini system.
Introduction
We built an electronic system using an Input-Processing-Output configuration. We
utilized the 555 integrated circuit. The first creation was that of a visual output in the
form of a flashing LED. The second was an audible representation, a speaker. This report
will display how to build the system, how the different components interact with each
other to form the system, and the different problems that can occur.
Learning Styles
As we prepared to construct the system, we viewed the diagram in the RadioShack
manual. From this, we determined that we learn the best visually. In developing the
project, we took a more active approach rather than reflective. Our hands-on work with
the system allowed us to better familiarize ourselves with it and increased our learning
and understanding. As our building continued, we learned from our errors and successes
and figured out how the system works as well as the roles the different parts play. In
addition to these learning styles, we opened ourselves up the Benjamin Bloom’s three
domains. In regard to the cognitive application, we learned about the LED flasher system,
and by studying it, we increased our understanding of it and were able to replicate it and
turn it into a speaker as well. For the affective application, when the system finally
worked, it made us happy. However, we came across problems along the way, which
frustrated and angered us. That anger and frustration was used to further motivated us to
diagnose the problems and fix them. The psychomotor application came into play as we
got hands on work with the system, which gave use an idea of how future systems might
operate and thus increased our knowledge and experience.
Team Building
Throughout working on the assignment, we learned that in order to complete a team
project, it is important that that team recognizes each other’s strengths and weaknesses
and splits up work to help eliminate stress and pressure. Putting each other’s brains
together is also very crucial because, for example, if one person isn’t able to think of a
solution to a problem, another team member can compensate for it and help out.

2. Basics
Figure 1. Components of the system
Figure 2. Circuit Diagram
Figure 1 displays the different items that were needed from the kit in order to construct
the IPO system. It requires a 555 IC, 3 resistors, a capacitor, and the LED. Figure 2
shows the different roles the components play. The input of the IPO system was the 6-
volt source that powered the circuit. A series of resistors process this input and limit the
amount of current going through the system so nothing is overloaded. The current is then
sent to the capacitor. The capacitor will store the charge and then discharge when full.
The charge then discharges into the 555, and finally the circuit directs the current to the
LED output.
Analysis
The circuit uses and input-processing-output system. The input is the 6-volt power
source, the resistors, capacitor, and 555 IC then processes that input and then sends the
charge to the LED output.
The two resistors on the left side as well as the capacitor determine the frequency of the
flashes.

3. Figure 3. Frequency equation
This constitutes what is called an RC time constant.
The current going into the LED is determined by the source as well as R3. Therefore,
increasing the amount of voltage going into the LED and/or decreasing R3 would
cause the LED to flash brighter.
Testing
We gathered all of the components needed for the system (LED, resistors, capacitor, 555)
and put them in their proper places on the breadboard. If the LED didn’t flash, we
checked to see if everything was secured in place and/or if anything was misplaced. One
of our initial errors that cause the LED not to flash was the fact that the system was not
grounded.
Figure 4. MultiSim computer simulation

4. After we constructed the physical electronic system on the RadioShack breadboard, we
utilized the computer program MultiSim and created a computer simulation of the
system. The simulation uses all of the same components as the real system. We put
everything together in the simulator and tested it to make sure everything worked as it
was supposed to. We even connected an oscilloscope to measure and observe what kind
of signal was going into the LED.
Another day, all of the parts in the physical system came apart so we had to reconstruct it.
Upon turning it on to see if it functioned properly, we noticed that the LED was flashing
but it was very dim and hard to see. We then started troubleshooting some of the possible
issues. First, we changed the batteries of the breadboard just in case they were faulty.
After changing them, the LED was still flashing dimly. Then, we used a multimeter to
measure the strength of the current. Everything seemed fine, so we turned on the system
again and still no change was made. We proceeded to ensure that the right resistors were
in the right places and that we had the right capacitor. Next, we thought the 555 IC might
be at fault so we carefully removed it and replaced it with a different one. After doing so,
still nothing changed. Finally, we thought to change the LED and then it flashed
normally. However, when we changed the output from the LED to the speaker, the sound
was very faint. We went through the troubleshooting process and unfortunately, we were
unable to determine the cause of the faint speaker.
Other Applications
Figure 5. Speaker
After working with the LED long enough, we decided to change it up a little bit. We
replaced the LED with a speaker, as shown in figure 5. Everything else works pretty
much the same, except now instead of a blinking light, the speaker plays a beeping noise.

5. Figure 6. Sim with a second LED
Additionally, we did more work with MultiSim and attached a fourth resistor as well as a
second LED. Now, when turning on the system, the two LEDs alternate.
Conclusion
Through working on this project, we found out that we learn better visually rather than
verbally, as we were able to construct the circuit by looking at the diagram in the
RadioShack workbook. We were able to see how Bloom’s Taxonomy applied to us in a
project environment. Using MultiSim, we were able to reconstruct the system with a
computer program. Finally, we were able to experience how to create two different IPO,
one with an LED and one with a speaker, as well as an electronic simulation of
alternating LEDs.
References
[1] Mims III, F. M., “Electronic Sensorlab Workbook,” RadioShack, Fort Worth, TX.
[2] Mims III, F. M., “Basic Electronics Workbook I,” RadioShack, Fort Worth, TX.