Holla,
For the past few weeks, I have been really busy doing my Final Year Project (FYP). I am so restless and tired, and the everytime I remember that I am far behind schedule and there is still much to do before I can finish my FYP, makes me nervous that I push myself hard to give my all to finish my project no matter what. Even worst, that the deadline of this project is just around the corner....Sob2....Hope I can finish on time.
Okay enough with my babbling. So as for today I am going to update you guys with my Heart Rate circuit as promise. This will be my last circuit and I am really excited to share with you guys.... :D
What is Hear Beat/ Pulse?
A heartbeat has two
parts. They are sometimes called lubb and dubb because those
are the sounds that a doctor hears. A lubb happens when the
upper chambers of the heart contract to squeeze the blood
downward into the ventricles. A dubb happens when the lower
chambers contract.
| Figure 1: Diagram of Heart Structure |
Every time the lower chambers of the heart contract, the blood in the left ventricle rushes upward into the aorta. It quickly speeds away from the heart causing the aorta to expand as it passes. As the blood races along, some of it pushes into the first artery that branches off from the aorta. Some of the blood enters the next artery. The blood from each contraction of the heart produces a bulge in the artery. We call that bulge a pulse. One pulse equals one heartbeat.
Source: http://www.ebsinstitute.com/Baseball/EBS.crb1df.html
What is Heart Rate?
Heart rate is determined by the number of heartbeats per unit of time,
typically expressed as beats per minute (BPM), it can vary with as the
body's need for oxygen changes, such as during exercise or sleep.
Source: http://www.news-medical.net/health/What-is-Heart-Rate.aspx
Construction of PCB for Heart Rate
Last weekend, I went to Pasar Road to fetch myself some components to make this Heart Rate circuit. After a stressful week working on this PCB, I have successfully finish the PCB. Now I will reveal my work of arts, here you go. tADAAAA......!
Figure 2: Heart Rate PCB
As you can see in Figure 2, I used 7 resistors and 2 of it is a variable resistor, an amplifier, 3 LED's including 1 super bright LED, 3 capacitors and 1 Light Dependent Resistor (LDR).
Figure 3: Side view of the PCB
Sorry for the blurry image, I'm using a cheap handphone with a very bad image resolution....haha.... Let's now see my bad soldering technique...hehe
Figure 4: Soldering of the PCB
Concept of LDR
Light-dependent resistor, alternatively called an LDR, photoresistor, photoconductor, or photocell,
is a variable resistor whose value decreases with increasing incident
light intensity.
An LDR is made of a high-resistance semiconductor.
If light falling on the device is of high intensity then it will lower the resistance value of the LDR, whereas if the intensity of light is low then it will increase the resistance value of the LDR.
Besides that, the bigger the LDR the better sensitivity it has. That is why I am using a large LDR (thumb-size surface diameter is the most suitable, as the LDR can cover the whole thumb, to get the most accurate output during Heart Rate measurement)
If light falling on the device is of high intensity then it will lower the resistance value of the LDR, whereas if the intensity of light is low then it will increase the resistance value of the LDR.
Besides that, the bigger the LDR the better sensitivity it has. That is why I am using a large LDR (thumb-size surface diameter is the most suitable, as the LDR can cover the whole thumb, to get the most accurate output during Heart Rate measurement)
Circuit Operation
As for my project, I am using super bright red LED for my project. The LED is use as the transmitter and the LDR is use as the receiver. Refer Figure 5, this is how I place my LDR and LED, where its facing towards each other.
Once the circuit is given a 5 Volt DC supply, The LED will continuously flash red light onto the LDR surface as in Figure 6. This indicates that the circuit works, so after programming the PIC, hopefully it can produce accurate output for Heart Rate measurement. Wish me luck people! :)
As for my project, I am using super bright red LED for my project. The LED is use as the transmitter and the LDR is use as the receiver. Refer Figure 5, this is how I place my LDR and LED, where its facing towards each other.
Figure 5: Placement of the sensor receiver and transmitter
Figure 6: Functional circuit
That's it for today. Hope you like what you read today.. :D I was hoping that I could update more on my progress..Next week, I will show all my circuits, including those from the first week till the latest one. See you next week. Tata for now!
Bubye :)
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Quote of the day.....!
Spread joy. Chase your wildest dreams. ~Patch Adams
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With lots of luv,
Idriah Safriza :p
