Electronics Design Laboratory
Lecture #10, Spring 2016
ECEN 2270
Electronics Design Laboratory
1
Lessons from Experiment 4
• Code debugging:
– Use print statement
• Circuit debugging:
– Re‐check operation of the speed sensor, driver, speed controller
– Clean up the circuit
• Neat layout helps reduce parasitics, reduces errors, helps in debugging
• Drop short wires from Arduino pins down to the breadboard next to Arduino, then route connections neatly from there
• Do not forget to include decoupling caps next to each chip
• Include 1K (or larger) resistors between encoder outputs and Arduino
interrupt pins
• Use scope to check encoder pulses; noise may generate spurious interrupts
ECEN 2270
Electronics Design Laboratory
2
Look Ahead: Project (Experiment 6)
• About 3 weeks total, 6 sessions, including final demo
• Must rely on fully functional Lab 2‐5 circuits
• Must include an additional analog circuit‐design hardware component. Programming only add‐ons or enhancements do not count.
• Some possible topics: – Additional sensors (light, IR, ultrasonic, audio, …)
– Additional actuators (light, audio, …)
– More advanced wireless control
ECEN 2270
Electronics Design Laboratory
3
Experiment 5 and Final Project
• Experiment 5 time will be split between preparing for your final project and designing a wireless controller for your robot
• Final Project
– Start working on final project ideas
• Milestone 1 (week of March 28): informal discussion about project ideas
• Milestone 2 (week of April 4): final project ideas and possible parts lists
• Project proposal presentations due Sunday, April 10. Each group will present in class on Monday, April 11
• Written project proposals are due Wednesday, April 13
• Experiment 5
– Build the components of a wireless on/off and speed control circuit – Write code for the Arduino to receive/set a threshold on an analog control signal for on/off control and to measure the duty‐cycle of a digital input for speed control
– Demonstrate wireless on/off and speed control of the robot
ECEN 2270
Electronics Design Laboratory
4
Wireless Control
5VDC
5VDC
5VDC
Wireless
Controller
Transmitter
Receiver
5VDC
Robot
(Arduino)
vrx
vtx
0
0
433.92 MHz RF
• Wireless controller generates PWM signal to be sent to Robot
• Wireless channel: use transmitter and receiver boards to encode and transfer signal vtx to receiver side vrx wirelessly
• Receiver translates RF signal into a 0‐5V signal
• Robot Arduino receives the same PWM signal that was sent by the wireless controller
ECEN 2270
Electronics Design Laboratory
5
Wireless Transmitter/Receiver
1.
2.
3.
•
•
•
•
Series of pulses is sent to the wireless transmitter
When input is high, transmitter outputs a 434MHz signal. This signal is applied to the transmitters antenna and travels through the air
A receiver tuned to the same frequency outputs a high value when it senses a signal on its antenna
vtx
0
RF
vrx
0
Wireless transmitter modulates a signal at a specific frequency
This is OK if only one person needs to transmit at a time
If a lab full of people all try and transmit at 434MHz…
Need a way for everyone to use the same frequency without interfering with each other
ECEN 2270
Electronics Design Laboratory
6
Wireless Transmitter/Receiver
• Modulate our modulated signal!
• Our transmitters have a center frequency of 434MHz
• Switch this signal on an off at a much lower frequency creates side‐bands
• These sidebands can then be filtered out later
• Solution for single transmission frequency in a busy lab
– Each group will have its own modulation frequency
– The RF spectrum of the lab will then be filtered for that frequency
ECEN 2270
Electronics Design Laboratory
7
Wireless Transmitter/Receiver
Data
1/fm
vtx
1/fc
RF
vrx
Data
• Carrier frequency fc is fixed at 434 MHz
• Modulation frequency fm is between 400 Hz an 1 kHz
• By filtering vrx the sent data can be re‐created
ECEN 2270
Electronics Design Laboratory
8
Wireless Control: Six Blocks Needed
5VDC
Wireless
Controller
5VDC
Modulator
5VDC
Transmitter
Receiver
5VDC
Filter
Robot
(Arduino)
433.92 MHz RF
Wireless Controller generates high/low signal
Modulator turns high/low into pulsed waveform at frequency fm
Transmitter generates RF signal at 433 MHz
Receiver receives RF signal at 433 MHx
Filter removes all frequency that we didn’t send, i.e. all frequency other than fm
– Robot does stuff
–
–
–
–
–
ECEN 2270
Electronics Design Laboratory
9
Wireless Control
5VDC
Wireless
Controller
5VDC
Modulator
Transmitter
5VDC
Receiver
5VDC
Filter
Robot
(Arduino)
• Inputs: on/off
• Outputs: 0‐5 V PWM signal at fm
ECEN 2270
Electronics Design Laboratory
10
Wireless Control
5VDC
Wireless
Controller
5VDC
Modulator
Transmitter
5VDC
Receiver
5VDC
Filter
Robot
(Arduino)
fm = 1.44/(C*(RA+2RB))
D = (RA+RB)/(RA+2RB)
Output
vtx
5VDC
1/fm
RA
RB < ½RA
Input
Data
C = 0.01μF
0.01μF
Astable Operation
ECEN 2830
Electronics Design Laboratory
11
Wireless Control
5VDC
Wireless
Controller
5VDC
Modulator
Transmitter
5VDC
Receiver
5VDC
Filter
Robot
(Arduino)
• Input: 0‐5 V PWM signal at fm
• Output: messy signal containing many frequencies in additional to the one we want
ECEN 2830
Electronics Design Laboratory
12
Transmitter (Tx)
WRL‐10534
4 3 2 1
876 5
4321
1234
5 6 78
1 23 4
Pin 1: GND
Pin 2: Data In (0‐to‐VCC pulses vtx)
Pin 3: VCC (5V to 10V)
Pin 4: Antenna
ECEN 2270
Receiver (Rx)
WRL‐10532
Pin 1: GND
Pin 2: Data Out (0‐to‐Vbat pulses vrx)
Pin 3: analog out (not used in the experiment)
Pin 4: +5V (NOT 10V!!)
Pin 5: +5V (NOT 10V!!)
Pin 6: GND
Pin 7: GND
Pin 8: Antenna (about 13 ‐ 17cm)
Electronics Design Laboratory
13
Transmitter & Receiver Design Notes
• Follow standard circuit prototyping practices: connect all supply and ground pins, include decoupling capacitors in the close proximity of the supply pins (47 F electrolytic and 0.1 F ceramic)
• If data input vtx pulses are too long (more than about 10 ms), or too short (less than about 0.5 ms), the receiver output vrx will be noisy
• Performance will depend on Tx and Rx location and distance. Wire antennas can be used to improve performance (note: /4 = (c/f)/4 = 17 cm)
• Tx and Rx can be tested separately using the lab waveform generator, and two lab power supply voltages (set both to +5V)
• Multiple transmitters operating at the same time will interfere with each other
ECEN 2270
Electronics Design Laboratory
14
Wireless Control
5VDC
Wireless
Controller
5VDC
Modulator
Transmitter
5VDC
Receiver
5VDC
Filter
Robot
(Arduino)
• Input: Messy signal containing many frequencies in additional to the one we want
• Output: High when fm is present at input, low when fm is absent from input
ECEN 2270
Electronics Design Laboratory
15
Wireless Control
5VDC
5VDC
Wireless
Controller
Modulator
5VDC
Receiver
Transmitter
5VDC
Filter
Robot
(Arduino)
• Bandpass filter will attempt to remove all frequencies that we don’t want
Gain
Passband Gain
Center Frequency
Quality Factor ‘Q’ determines how wide peak is. High Q means narrow passband.
1
fm
ECEN 2830
Electronics Design Laboratory
Frequency
16
Wireless Control
5VDC
Wireless
Controller
5VDC
Modulator
5VDC
Receiver
Transmitter
5VDC
Filter
Robot
(Arduino)
• Bandpass filter will attempt to remove all frequencies that we don’t want
Gain
Gain
Group Y
Group X
1
1
fm
ECEN 2270
Frequency
Electronics Design Laboratory
fm
Frequency
17
Wireless Control
5VDC
5VDC
Wireless
Controller
Modulator
3
5VDC
Transmitter
5VDC
Filter
Receiver
Robot
(Arduino)
1
2
10nF
R3
10nF
R1
5VDC
2
3
R2
47kΩ 5VDC
47kΩ
ECEN 2270
0.1μF
Electronics Design Laboratory
18
Band‐Pass Filtering
Group X
Gain
Group Y
Group X
1
My Robot
fm
Frequency
fm
Frequency
Gain
Group Y
1
ECEN 2270
Electronics Design Laboratory
19
Wireless Control
5VDC
5VDC
Wireless
Controller
Modulator
5VDC
Transmitter
Receiver
5VDC
Filter
Robot
(Arduino)
1
10nF
R3
10nF
R1
5VDC
2
3
R2
47kΩ 5VDC
47kΩ
ECEN 2270
0.1μF
Electronics Design Laboratory
20
Output of Band‐Pass Filter
My Robot – 4.3V Output 5VDC
Receiver
R3
10nF
Filter
Robot
(Arduino)
Group X – 2.8V Output
10nF
R1
5VDC
Peak Detector
5VDC
2
4
R2
3
Group Y – 3.4V Output
47kΩ 5VDC
47kΩ
ECEN 2270
0.1μF
Electronics Design Laboratory
21
Amplitude Detector: Peak Detector and Comparator
5VDC
5VDC
Wireless
Controller
•
Modulator
5VDC
Receiver
Transmitter
Input: Messy signal containing many frequencies in additional to the one we want
10nF
R3
10nF
R1
5VDC
•
5VDC
Filter
Robot
(Arduino)
Output: High when fm is present at input, low when fm is absent from input
Peak Detector
Comparator
Input
5VDC
R2
Output
47kΩ 5VDC
47kΩ
ECEN 2270
0.1μF
5VDC
R5
Electronics Design Laboratory
R4
0.1μF
22
Amplitude Detector: Peak Detector and Comparator
• Input: Messy signal containing many frequencies in additional to the one we want
• Output: High when fm is present at input, low when fm is absent from input
Input
Output
10nF
R3
10nF
R1
5VDC
Peak Detector
Comparator
Input
5VDC
R2
Output
47kΩ 5VDC
47kΩ
ECEN 2270
0.1μF
5VDC
R5
Electronics Design Laboratory
R4
0.1μF
23