Wiki

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
university:courses:electronics:electronics-lab-led-sensor [04 Aug 2017 12:19]
Markus Persson [Background:] Corrected quadrant #3 description.
university:courses:electronics:electronics-lab-led-sensor [25 Jun 2020 22:07] (current)
Line 31: Line 31:
  
 =====Hardware Setup:===== =====Hardware Setup:=====
 +
 +{{:​university:​courses:​electronics:​led_single_emitter-bb.png|}}
 +
 +<WRAP centeralign>​ Figure 2 LED and single common emitter NPN light sensor Breadboard Circuit </​WRAP>​
 +
 Use the variable positive power supply from the ADALM2000 module set to +5 V to power your circuit. Use scope channel 1 to monitor the voltage at the collector node of Q<​sub>​1</​sub>​. Use the variable positive power supply from the ADALM2000 module set to +5 V to power your circuit. Use scope channel 1 to monitor the voltage at the collector node of Q<​sub>​1</​sub>​.
  
Line 36: Line 41:
  
 Insert a red, yellow or green LED into the circuit as shown one at a time. Try exposing the three different color LEDs from your ADALP2000 Analog Parts Kit to different light sources such as standard incandescent,​ florescent and LED lights held at differing distances from the LED sensor. Observe the voltage waveform seen at the collector of Q<​sub>​1</​sub>​. Try inserting the infrared LED from your kit and observing how it responds to the light from the different sources. Try increasing the sensitivity or gain by increasing the value of R<​sub>​L</​sub>​ to 200KΩ or 470KΩ. Insert a red, yellow or green LED into the circuit as shown one at a time. Try exposing the three different color LEDs from your ADALP2000 Analog Parts Kit to different light sources such as standard incandescent,​ florescent and LED lights held at differing distances from the LED sensor. Observe the voltage waveform seen at the collector of Q<​sub>​1</​sub>​. Try inserting the infrared LED from your kit and observing how it responds to the light from the different sources. Try increasing the sensitivity or gain by increasing the value of R<​sub>​L</​sub>​ to 200KΩ or 470KΩ.
 +
 +{{:​university:​courses:​electronics:​led_single_emitter_wav1.png|}}
 +
 +<WRAP centeralign>​ Figure 3 Red LED and single common emitter NPN light sensor - Led light max distance </​WRAP>​
 +
 +{{:​university:​courses:​electronics:​led_single_emitter_wav2.png|}}
 +
 +<WRAP centeralign>​ Figure 4 Red LED and single common emitter NPN light sensor - Led light medium distance </​WRAP>​
 +
 +{{:​university:​courses:​electronics:​led_single_emitter_wav3.png|}}
 +
 +<WRAP centeralign>​ Figure 5 Red LED and single common emitter NPN light sensor - Led light min distance </​WRAP>​
 +
  
 =====Step 2 Directions:​===== =====Step 2 Directions:​=====
  
-Change the circuit on your breadboard to the Darlington configuration shown in figure ​2. Be sure to turn off the power supply before making any changes to the circuit. With the Darlington connected transistors the emitter current of Q<​sub>​2</​sub>​ becomes the base current of Q<​sub>​1</​sub>​ such that the photo generated current from the LED D<​sub>​1</​sub>​ is now multiplied by ß<​sup>​2</​sup>​ and will appear in the load resistor R<​sub>​L</​sub>​ from the collectors of Q<​sub>​1</​sub>​ and Q<​sub>​2</​sub>​. Because of this much higher current gain we can use a much lower value load resistor.+Change the circuit on your breadboard to the Darlington configuration shown in figure ​6. Be sure to turn off the power supply before making any changes to the circuit. With the Darlington connected transistors the emitter current of Q<​sub>​2</​sub>​ becomes the base current of Q<​sub>​1</​sub>​ such that the photo generated current from the LED D<​sub>​1</​sub>​ is now multiplied by ß<​sup>​2</​sup>​ and will appear in the load resistor R<​sub>​L</​sub>​ from the collectors of Q<​sub>​1</​sub>​ and Q<​sub>​2</​sub>​. Because of this much higher current gain we can use a much lower value load resistor. 
 + 
 +{{ :​university:​courses:​electronics:​aleds_f2.png?​600 |}} 
 + 
 +<WRAP centeralign>​ Figure 6 LED and Darlington connected NPN light sensor </​WRAP>​ 
 + 
 +=====Step 2 Hardware Setup:​===== 
 + 
 +{{:​university:​courses:​electronics:​led_darlington-bb.png|}} 
 + 
 +<WRAP centeralign>​ Figure 7 LED and Darlington connected light sensor Breadboard Circuit </​WRAP>​
  
 =====Step 2 Procedure:​===== =====Step 2 Procedure:​=====
Line 45: Line 73:
 Repeat the same procedure of inserting the various LEDs into the circuit for D<​sub>​1</​sub>​ and measuring the response to the various light sources and record them in your lab report. Repeat the same procedure of inserting the various LEDs into the circuit for D<​sub>​1</​sub>​ and measuring the response to the various light sources and record them in your lab report.
  
-{{ :​university:​courses:​electronics:​aleds_f2.png?600 |}}+{{:​university:​courses:​electronics:​led_darlington_wav1.png|}} 
 + 
 +<WRAP centeralign>​ Figure 8 Red LED and Darlington connected light sensor - Led light max distance </​WRAP>​ 
 + 
 +{{:​university:​courses:​electronics:​led_darlington_wav2.png|}} 
 + 
 +<WRAP centeralign>​ Figure 9 Red LED and Darlington connected light sensor - Led light medium distance </​WRAP>​ 
 + 
 +{{:​university:​courses:​electronics:​led_darlington_wav3.png|}} 
 + 
 +<WRAP centeralign>​ Figure 10 Red LED and Darlington connected light sensor - Led light min distance </​WRAP>​
  
-<WRAP centeralign>​ Figure 2 LED and Darlington connected NPN light sensor </​WRAP>​ 
  
 =====Questions:​===== =====Questions:​=====
Line 54: Line 91:
  
 How does the sensitivity of the Darlington connected configuration compare to the single common emitter configuration?​ Are the minimum and maximum voltages the same for both configurations?​ If not, why? How does the sensitivity of the Darlington connected configuration compare to the single common emitter configuration?​ Are the minimum and maximum voltages the same for both configurations?​ If not, why?
 +
 +<WRAP round download>​
 +**Resources:​**
 +  * Fritzing files: [[downgit>​education_tools/​tree/​master/​m2k/​fritzing/​led_light_sensor_bb | led_light_sensor_bb]]
 +  * LTspice files: [[downgit>​education_tools/​tree/​master/​m2k/​ltspice/​led_light_sensor_ltspice | led_light_sensor_ltspice]]
 +</​WRAP>​
  
 **For Further Reading:** **For Further Reading:**
university/courses/electronics/electronics-lab-led-sensor.1501841998.txt.gz · Last modified: 04 Aug 2017 12:19 by Markus Persson