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university:courses:alm1k:alm-lab-heart-rate-mon [24 Nov 2017 21:26] – [Questions] Doug Merceruniversity:courses:alm1k:alm-lab-heart-rate-mon [14 May 2022 16:31] (current) – [Questions] Doug Mercer
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 =====Background===== =====Background=====
  
-A type of Heart Rate Monitor consists of an electronic circuit that monitors heartbeat by clipping onto a finger tip. It does this by shining light into or through your finger and measuring how much light is reflected or absorbed. This goes up and down as blood is pumped through your finger. For the operation as a optical heartbeat detector, a pair of IR LED and Phototransistor is used. The LED emits light into or through the finger and the reflected or transmitted light is detected by the phototransistor, which acts like a variable current source conducting different amounts of current depending on the light received. +A type of Heart Rate Monitor consists of an electronic circuit that monitors heartbeat by clipping onto a finger tip. It does this by shining light into or through your finger and measuring how much light is reflected or absorbed. This goes up and down as blood is pumped through your finger. For the operation as a optical heartbeat detector, a combination of an Infrared LED and Photo transistor is used. The LED emits light into or through the finger and the reflected or transmitted light is detected by the photo transistor, which acts like a variable current source conducting different amounts of current depending on the light received. 
  
-The voltage variations change with the heartbeat and are acquired from the collector of the phototransistor. The small signal obtained is used as input for the following circuit, providing an output signal as a heartbeat detector or monitor. +The voltage variations change with the heartbeat and are acquired from the collector of the photo transistor. The small signal obtained is used as input for the following circuit, providing an output signal as a heartbeat detector or monitor. 
  
 In order to have a relevant output, the input signal is passed through multiple circuits: In order to have a relevant output, the input signal is passed through multiple circuits:
   *Preamplifier - the output signal from the heartbeat measurement setup is decoupled through the series capacitor and amplified using a negative feedback resistor(R4).   *Preamplifier - the output signal from the heartbeat measurement setup is decoupled through the series capacitor and amplified using a negative feedback resistor(R4).
   *Low-Pass Filter - RC filter that cuts the high frequencies (noise).   *Low-Pass Filter - RC filter that cuts the high frequencies (noise).
-  *[[university:courses:electronics:electronics-lab-1|Voltage Follower]] - buffers the output of the low-pass filter and reproduces its voltage with a low impedance output; +  *[[university:courses:alm1k:alm-lab-1|Voltage Follower]] - buffers the output of the low-pass filter and reproduces its voltage with a low impedance output; 
-  *[[university:courses:electronics:electronics-lab-1|Inverting Amplifier]] with Low-Pass Filter - amplifies the voltage signal and cuts the high frequencies (noise);+  *[[university:courses:alm1k:alm-lab-1|Inverting Amplifier]] with Low-Pass Filter - amplifies the voltage signal and cuts the high frequencies (noise);
  
 =====Materials===== =====Materials=====
 +
 +Select the following components from the ADALP2000 Analog Parts Kit. Note, the parts kit contains both OP-482 and OP-484 quad op-amps. They look very similar and are both in 14 pin DIP packages. The laser branding on the packages can be hard to read. Fortunately they share a common pinout so you will not damage them if you use the wrong one in this experiment by accident. The circuit will just not operate properly.
 +
 +There are two black plastic devices with two leads in the kit that look almost exactly the same. One is the photo transistor and the other is a photo diode. The one with the slightly shorter leads should be the photo transistor. If you have a DMM with a diode test function handy you can verify which is the photo diode and which is the photo transistor (the photo diode will conduct in one direction and the photo transistor will not conduct in either direction) 
  
 ADALM1000 Active Learning Module\\ ADALM1000 Active Learning Module\\
 Solder-less breadboard\\ Solder-less breadboard\\
 Jumper wires\\ Jumper wires\\
-1 - OP484 precision rail-to-rail I/O op amp\\ +1 - OP484 precision rail-to-rail I/O op amp (14 pin DIP package)\\ 
-1 - 100Ω resistor\\ +{{ :university:tools:adalp2000:op484.jpg?250 |}} 
-1 - 220Ω resistor\\ +<WRAP centeralign> **OP484 Quad op-amp** </WRAP> 
-1 - 470Ω resistor\\ + 
-1 - 1.5KΩ resistor\\ +Resistors are marked with color bands like this:\\ 
-1 - 10KΩ resistor\\ +{{ :university:tools:adalp2000:20k.jpg?250 |}} 
-2 - 22KΩ resistor\\ + 
-2 - 1uF capacitor\\+Find resistors with the following color bands:\\ 
 +1 - 100Ω resistor (brown black brown)\\ 
 +1 - 470Ω resistor (yellow purple brown)\\ 
 +1 - 1KΩ resistor (brown black red)\\ 
 +1 - 1.5KΩ resistor (brown green red)\\ 
 +1 - 10KΩ resistor (brown black orange)\\ 
 +1 - 20KΩ resistor (red black orange)\\ 
 +1 - 47KΩ resistor (yellow purple orange)\\ 
 + 
 +2 - 1uF capacitors\\ 
 +{{ :university:courses:alm1k:1uf.jpg?250 |}} 
 1 - 47uF capacitor\\ 1 - 47uF capacitor\\
-1 - Infrared LED ( QED-123 )\\ +{{ :university:courses:alm1k:47uf.jpg?250 |}} 
-1 - Infrared Transistor ( QSD-123)\\ + 
-1 - Red LED+1 - Infrared LED (QED-123) the longer of the two leads is the anode (+) and the shorter lead is the cathode (-). \\
 {{ :university:courses:electronics:a22_g1.jpg?250 |}} {{ :university:courses:electronics:a22_g1.jpg?250 |}}
  
 <WRAP centeralign> **QED-123 Infrared LED** </WRAP> <WRAP centeralign> **QED-123 Infrared LED** </WRAP>
 +
 +1 - Infrared Transistor (QSD-123) the longer of the two leads is the collector and the shorter lead is the emitter.\\
  
 {{ :university:courses:electronics:a22_g2.jpg?250 |}} {{ :university:courses:electronics:a22_g2.jpg?250 |}}
  
 <WRAP centeralign> **QSD123 Infrared Transistor** </WRAP> <WRAP centeralign> **QSD123 Infrared Transistor** </WRAP>
 +
 +1 - Red LED
 +{{ :university:tools:adalp2000:leds.jpg?250 |}}
 =====Directions===== =====Directions=====
  
-On your solder-less breadboard construct the heartbeat monitor circuit as shown in figure 1. +On your solder-less breadboard construct the heartbeat monitor circuit as shown in figure 1. The values shown for the gain setting resistors R<sub>5</sub> and R<sub>6</sub> are approximate and may need to be adjusted based on the response of the person who's heart rate is being monitored. Increasing or decreasing the ratio may be needed to obtain an optimal output signal amplitude that fits within the available 0 to 5V range. 
 + 
 +The collector load resistor R<sub>2</sub> of the photo transistor can also be adjusted to optimally center the signal.
  
 {{ :university:courses:alm1k:alm_fig1_heart-rate-mon.png?750 |}} {{ :university:courses:alm1k:alm_fig1_heart-rate-mon.png?750 |}}
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 <WRAP centeralign>Figure 1 Heartbeat Monitor Circuit</WRAP> <WRAP centeralign>Figure 1 Heartbeat Monitor Circuit</WRAP>
  
-The circuit uses quad OP484FPZ from the ADALP2000 Analog Parts Kit, the schematic design was implemented with three of the Precision Rail-to-Rail Operational Amplifiers. They operate from a single supply (+5V) from the ADALM1000 module.+The circuit uses the OP484FPZ quad opamp from the ADALP2000 Analog Parts Kit, the schematic design was implemented with three of the Precision Rail-to-Rail Operational Amplifiers. They operate from a single supply (+5V) from the ADALM1000 module.
  
 ====IR LED==== ====IR LED====
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 =====Simulation===== =====Simulation=====
  
-Considering the circuit designed in LTSpice or ADIsimPE, two types of simulation are preformed:+Considering the circuit designed in LTSpice or ADIsimPE, two types of simulation are performed:
   *Transient - Connect at the input of the circuit a waveform generation source. Configure the source to generate a sine with amplitude of 250uV, frequency 2Hz and 500mV offset. Observe the output signal amplitude in order to determine graphically the total gain of the circuit(Figure 2).   *Transient - Connect at the input of the circuit a waveform generation source. Configure the source to generate a sine with amplitude of 250uV, frequency 2Hz and 500mV offset. Observe the output signal amplitude in order to determine graphically the total gain of the circuit(Figure 2).
  
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 =====Procedure===== =====Procedure=====
  
-The Heart Rate monitor can operate in either of two modes. In the first mode, as shown on the left of figure 4, the light form the LED is reflected as it passes into the tip of the finger and bounces back into the photo transistor. Arrange the LED and photo transistor right next to each other both facing up. It might be useful to shorten the leads so that they sit against the breadboard surface. In the second mode, as shown on the right of figure 4, the light from the LED passes through the tip of the finger and into the photo transistor on the other side. Put the tip of your finger between the IR LED (D1) and the Photo transistor (Q1). The emitter and the receiver should be aligned and pointing one to another.+The Heart Rate monitor can operate in either of two modes. In the first mode, as shown on the left of figure 4, the light from the LED is reflected as it passes into the tip of the finger and bounces back into the photo transistor. Arrange the LED and photo transistor right next to each other both facing up. It might be useful to shorten the leads so that they sit against the breadboard surface. In the second mode, as shown on the right of figure 4, the light from the LED passes through the tip of the finger and into the photo transistor on the other side. Put the tip of your finger between the IR LED (D1) and the Photo transistor (Q1). The emitter and the receiver should be aligned and pointing one to another.
  
 {{ :university:courses:alm1k:alm_lab_heart-rate-mon-2modes.png?500 |}} {{ :university:courses:alm1k:alm_lab_heart-rate-mon-2modes.png?500 |}}
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 The red LED should blink on and off once per heart beat, about once per second. The red LED should blink on and off once per heart beat, about once per second.
  
-Observe the voltage waveform seen at the the output of the 3rd stage op amp (A<sub>3</sub>). The signal is very slow, low frequency, and is best viewed using the Alice M1K Strip Chart tool. Start the Strip Chart and select CH-A oon 1 grid, then hit Run.  An example of the output waveform is shown in Figure 5.+Observe the voltage waveform seen at the the output of the 3rd stage op amp (A<sub>3</sub>). The signal is very slow, low frequency, and is best viewed using the Alice M1K Strip Chart tool. Start the Strip Chart and select CH-A on 1 grid, then hit Run.  An example of the output waveform is shown in Figure 5.
  
 {{ :university:courses:alm1k:alm_lab_heart-rate-mon-wave.png?750 |}} {{ :university:courses:alm1k:alm_lab_heart-rate-mon-wave.png?750 |}}
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   * Download: {{:university:courses:electronics:heartbeat-bb-dl.zip|Breadboard Circuit - Fritzing}}   * Download: {{:university:courses:electronics:heartbeat-bb-dl.zip|Breadboard Circuit - Fritzing}}
 </WRAP> </WRAP>
 +**For further reading:**
 +
 +[[wp>Photoplethysmogram|Photoplethysmogram]]\\
 +[[wp>Heart_rate_monitor|Heart rate monitor]]
 +
 **Return to Lab Activity [[university:courses:alm1k:alm-labs-list|Table of Contents]].** **Return to Lab Activity [[university:courses:alm1k:alm-labs-list|Table of Contents]].**
university/courses/alm1k/alm-lab-heart-rate-mon.1511555187.txt.gz · Last modified: 24 Nov 2017 21:26 by Doug Mercer

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