electronics design laboratory lecture #11ecee.colorado.edu/ecen2270/lectures/lecture11.pdf · speed...
TRANSCRIPT
Project• Must rely on fully functional Lab 2‐4 circuits, Lab 5 circuit is optional– Can re‐do wireless or replace it with a different control method if desired. The project does not have to include remote control.
• Must include an additional hardware component. Programming only add‐ons or enhancements do not count.
• When selecting components check– Range– Voltage– Communication
Electronics Design Laboratory 2ECEN 2270
Sensors• Range
– Ultrasonic– Infrared– Buttons
• Position– Compass– Accelerometer– Gyros– GPS– Tilt
• Sound– Voice Recognition– Microphone– Speakers
• Environment– Temperature– Humidity– Altitude– Pressure– Light (LDR, etc)
• Physical– Pressure– Flex– Vibration– Buttons
• Other– RFID– ZigBee– Bluetooth– Other wireless
Electronics Design Laboratory 3ECEN 2270
Actuators• Your robot• Motors
– DC (Brushed or Brushless)– Stepper– Servo– Linear– Solenoid
• LEDs– Single Color– RGB w/ PWM control– Infrared– 7 segment
Arduino• Shields
– Motor/Stepper/Servo– GPS– Audio (wave, mp3, etc)– Ethernet– GSM– Wifi
• Larger controllers
Final Project and Experiment 5• Final Project
– Project ideas and discussions this week, additional parts you may need?
– Parts can take 1‐1.5 weeks to get here. Order early and order extras!
• Experiment 5– Lab 5A: build the components of a wireless on/off and speed control circuit (should be done Tuesday this week)
– Lab 5B: prelab due on Thursday• Write code for the Arduino to measure the on time of a digital input for speed control (should start this Thursday, finish Tuesday next week)
• Demonstrate wireless control of the robot, demo is Thursday next week
Electronics Design Laboratory 4ECEN 2270
Wireless Transmitter/Receiver
• Carrier frequency fc is fixed at 434MHz• Modulation frequency fm is much lower• By filtering vrx the sent data can be re‐created
Electronics Design Laboratory 5ECEN 2270
Data
RF
vtx
1/fm
1/fc
vrx
Data
0 fm 3fm 5fm fc0
0.5
1
1.5
AM Modulation of RF signal at 434 MHz
Electronics Design Laboratory 6ECEN 2830
0
0.5
1
1.5
0 1/fm 2/fm 3/fm
-1
-0.5
0
0.5
1
-1
-0.5
0
0.5
1
Sinu
soidal M
odulation
ON/O
FF M
odulation
(Amplitu
de Shift Keying (ASK
)
Time Domain Frequency Domain
CarrierModulationSignal
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
1
2
3
4
5
Volts
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
1
2
3
4
5
Seconds
Volts
RF Communication
Electronics Design Laboratory 7ECEN 2270
• Group A (Red Waveforms) wants to send a 1sec pulse starting at 100ms. Group A will use a fm = 500Hz modulation frequency
• Group B (Black Waveforms) wants to send a 1sec pulse as well, but starting at 500ms. Group B will use a fm = 1200Hz modulation frequency
• Both groups are going to try and send this signal wirelessly, using a 434MHz wireless transmitter/receiver pair
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
Group A Data
Group B Data
This is just an example of data sent by two groups
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
1
2
3
4
5
Volts
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
1
2
3
4
5
Seconds
Volts
RF Communication
Electronics Design Laboratory 8ECEN 2270
Both signals are modulated using a 555 timer oscillating at 500Hz for Group A, and 1.2kHz for Group B
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
5VDC
Input
Output
fm1 = 500Hz
fm2 = 1.2kHz
Group A Modulated Data
Group B Modulated Data
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-3
-2
-1
0
1
2
3
Volts
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-3
-2
-1
0
1
2
3
Seconds
Volts
RF Communication
Electronics Design Laboratory 9ECEN 2270
The RF transmitter modulates the signal a second time at the carrier frequency of 434 MHz
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
fc = 434 MHz
fm1 = 500Hz
fm2 = 1.2kHz
Group A RF Signal
Group B RF Signal
0 1 2-3
-2
-1
0
1
2
3
Volts
0 1 2-3
-2
-1
0
1
2
3
0 1 2-3
-2
-1
0
1
2
3
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
-5
0
5
Seconds
Intesity
RF Communication
Electronics Design Laboratory 10ECEN 2270
• Both RF transmitters are sending on the same frequency
• In addition, there is a noticeable amount of noise in most environments
• The result is an extremely messy signal, and this is with just two groups transmitting simple data pulses.
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
Group A Transmission
Group B Transmission RF Noise
Total RF noise and signal
RF Communication
Electronics Design Laboratory 11ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
• When neither transmitter is operating, the RF spectrum is dominated by noise
• This random noise floor is generally of a low magnitude and equally distributed across all frequencies
fc
Noise spectrum when no one is transmitting
RF Communication
Electronics Design Laboratory 12ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
fc
• When Group A begins to transmit, spikes in the frequency spectrum appear
• These spikes are much larger than the noise floor and at known frequencies!
fc+fm1fc‐fm1
RF Communication
Electronics Design Laboratory 13ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
fc+fm2fc‐fm2
fc
• When Group B begins to transmit, additional spikes in the frequency spectrum appear
• These spikes are at a different frequency than Group A’s transmissions!
• Neither signal overlaps with the other
RF Communication
Electronics Design Laboratory 14ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
fcfc
• An RF receiver acts as a demodulator
• This demodulation shifts the frequency spectrum such that fc = 434MHz is shifted to 0Hz
• Both Group A and Group B receivers are picking up everything
fm1 fm2
RF Communication
Electronics Design Laboratory 15ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
• Each group’s filter is tuned to their specific modulation frequency
• This is how we separate our signal from noise and other groups
5VDC
5VDC47kΩ
47kΩ 0.1μF
210nF
10nF
R3
R1
R23
fm1 fm2
Group A Filtered Output
Group B Filtered Output
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
2
4
Seconds
Magnitude
0
1
2
3
4
5
Seconds
Volts
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
1
2
3
4
5
Seconds
Volts
RF Communication
Electronics Design Laboratory 16ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
• Each groups filter is tuned to their specific modulation frequency
• This is how we separate our signal from noise and other groups
5VDC
5VDC47kΩ
47kΩ 0.1μF
110nF
10nF
R3
R1
R22
Group A Filtered Output
Group B Filtered Output
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
2
4
Seconds
Magnitude
0
1
2
3
4
5
Seconds
Volts
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
1
2
3
4
5
Seconds
Volts
RF Communication
Electronics Design Laboratory 17ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
• Each groups filter is tuned to their specific modulation frequency
• This is how we separate our signal from noise and other groups
Group A Filtered Output
Group B Filtered Outputfm2
18ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
RF Communication
• Peak detector follows the peak value of the waveform
• This value is a diode drop less than the real peak!
• We can use a comparator on this peak detector output in order to generate our pulse outputs.
Out
Peak Detector
Electronics Design Laboratory
In
0.05 0.1 0.15 0.2 0.250
2
4
Seconds
Magnitude
0
1
2
3
4
5
Seconds
Volts
0.08 0.085 0.09 0.095 0.1 0.105 0.11 0.115 0.120
1
2
3
4
5
Seconds
Volts
0.7V
0.7V
Vthreshold
Vthreshold
19ECEN 2270
Input Signal Transmitter Receiver Robot
(Arduino)Modulator Filter Peak Detector
Complete Receiver
Electronics Design Laboratory
5VDC
5VDC47kΩ
47kΩ 0.1μF
Input10nF
R3
R1
R2
Peak Detector
5VDC
5VDC
R40.1μFR5
Comparator
Output
vf vpd
Vthreshold
Filter should have a gain of 1 (0dB) at fm
When you are transmitting, vf should be a 0‐5V sinewave
centered around 2.5 V
RC time constant in the peak detector should be large enough
so that ripple in vpd is small. The peak detector output vpd
should be around 4 V when you are transmitting.
Comparator Vthreshold should be close to but below the (vpd)minwhen you are transmitting
0‐5 V digital data to Arduino