High school students complete Optoelectronics Summer Program
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Optoelectronics: Laser-Pulse-Activated Remote Control
By Michael Cimorosi, Adjunct Physics Instructor Department of Physics and Engineering, Delaware State University
During the week of June 27 to July 1, from 11 AM to 3 PM, four local high school students (Figure 1) engaged in a hands-on optoelectronics project. The mission was to build a system capable of controlling a computer fan activation time. Of course, a brief single laser pulse would serve as the trigger! The program took place in Room 211(EE Lab) in Mishoe Science Center South. The program was an OSCAR-sponsored event that awarded each student a stipend! So, the students not only had fun while they learned, but were also financially rewarded for their efforts. Thank you Jacquelyn Jones (Coordinator & Analyst of Student Activities OSCAR) for coordinating this program.
Let the fun begin! We’re ready.
Figure 1. (L-R) Jaren Kennedy (Early College High School), Dorian Baker (Dover High School), Dion Baker (Dover High School), and Ameen Zerrad (Dover High School)
A busy week, indeed!
Monday – Electromagnetic Relay
Following a brief introduction and orientation period, two student teams were formed. Each team was then issued a computer fan, electromagnetic relay, blue LED, red LED, green laser λo = 532 nm), IC chips, and other electronics components. The students then busied themselves constructing and testing an electromagnetic relay circuit. After the circuit was constructed, a little troubleshooting was required to find and correct a few wiring/component connections. Eventually, each team’s circuit worked as expected. As is often the case, when constructing electronics circuits, incorrect connections (I’ve made my share) happen and must be remedied. Welcome to the world of electronics!
Tuesday – Resistor and Capacitor Check
First thing in the morning, I discussed the details of a Resistor-Capacitor (RC) electrical circuit and its essential role in controlling the computer fan’s activation time. After that, each team measured resistors, experimentally determined capacitors, and compared them to nominal values. One team discovered that one issued capacitor was way out of specification. However, success was “in the cards” since the other capacitors were within 10% of nominal values. Don’t worry, the team that received the bad capacitor had it replaced with a good one!
Okay, I put this off long enough. It’s now time for a little “techie” talk: Resistors and capacitors determine the fan’s activation time. One team was issued a 1-MΩ (one MegaOhm, Mega means million) resistor, a 22-μF (microfarad) capacitor, and a 10-μF capacitor. The two different RC combinations produce fan activation times of 24.2 seconds and 11.0 seconds, respectively. The other team was issued a1-MΩ resistor, a 22-μF capacitor, and a 4.7-μF capacitor. The two different RC combinations produce fan activation times of 24.2 seconds and 5.2 seconds, respectively. For folks who like equations, the activation time can be calculated using
T = R C ln(3). That’s enough mathematics for this article.
Wednesday – Detector Circuit
The day started with the construction of a laser pulse detector circuit. Once built, each team spent a little time troubleshooting and correcting connection issues. One team met with success by the end of the day. However, the other team had additional connection issues and had to wait until Thursday morning before being welcomed by the opened arms of success!
Thursday – Timing Circuit
Most of this day was spent constructing the timing circuit. Eventually, each team completed the timing circuit and was ready to check out the entire system. Filled with anticipation, they watched as I used a white light LED to shine on a light-dependent resistor (LDR) to see if the computer fan would be activated for the expected time. Within minutes, the “crowd” exhaled with a sigh of relief. Both systems responded perfectly and were poised for a “date” with the laser on Friday morning!
Friday – Time to fire up the Laser!
In the morning, each team aligned the laser with the pentaprism used to deliver the laser pulse to the detector. After a little optical tweaking, each team’s Laser-Pulse-Activated Remote Control system worked perfectly. Check out Figures 2, 3, 4, and 5.
Figure 2. No pulse applied (blue LED on) Figure 3. Computer fan not activated
Figure 4. Laser pulse applied (red LED on) Figure 5. Computer fan activated
The measured activation times aligned with those calculated. This basic circuit used to control the computer fan’s activation time could also be used to control the precise burn time of a spacecraft’s rocket thruster!
After returning the equipment to its proper location, and before heading to the OSCAR building, each student anonymously completed a Program Follow-Up Questionnaire. Below is a sampling of questions with responses.
• Why did you elect to participate in this program?
One student responded, “To learn more about the optics program at DSU”
Another student responded, “For the experience”
Two students indicated that they received encouragement from parents!
• Did you find the experience of constructing, testing, and troubleshooting circuits interesting?
Every student responded, “Yes”
• Did you enjoy the general college atmosphere experience?
Every student responded, “Yes”
Figure 6. OSCAR building basking in blue Figure 7. Dr. Khan explaining sensors
Around 1:45 PM, we headed to the OSCAR building (Figure 6), where Dr. M. Amir Khan, Assistant Professor (Figure 7), discussed his latest laser research involving greenhouse gas emission sensors (try to say that fast, three times!). After the presentation, he gave us a guided tour of the OSCAR building. A great way to end the day! Thank you Dr. Khan.
Maybe in a year or two, one or more of these students will walk the halls of Delaware State University as an Engineering Physics major (track in Optical Engineering) with an eye toward graduate work or direct employment in the field of lasers and optics! DSU has the staff, the equipment, the time, and the facilities to prepare them.