Electronics Design Laboratory 1ECEN 2270

Electronics Design LaboratoryLecture #11, Fall 2014

Electronics Design Laboratory 2

Experiment 5 Tasks• Final Project– Start working on final project ideas– Milestone 1, informal discussion about project ideas –

November 11th

• Nothing due yet… I’ll stop by each lab bench to discuss your ideas.

• Experiment 5 Specific– Build the components of a wireless on/off and speed

control circuit (Part A, 1 week) – Write code for the Arduino to measure the on time of a

digital input for speed control (Part B, 1 week)– Demonstrate wireless on/off and speed control of the

robot, demo is on November 13th

ECEN 2270

Electronics Design Laboratory 3

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 ECEN 2270

Data

RF

vtx

1/fm

1/fc

vrx

Data

Electronics Design Laboratory 4

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

ECEN 2270

• Group A (Red Waveforms) wants to send a 1sec pulse starting at 100ms. Group A will use a 500Hz modulation frequency

• Group B (Black Waveforms) wants to send a 1sec pulse as well, but starting at 500ms. Group B will use a 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

Electronics Design Laboratory 5

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

ECEN 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 Data

Group B Data

Electronics Design Laboratory 6

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

ECEN 2270

• The RF transmitter modulates the signal a second time at the carrier frequency

• In this example, a 10kHz carrier frequency is used. The RF transmitters you will be using in the lab transmit at 434MHz

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

fc = 10kHz

fm1 = 500Hz

fm2 = 1.2kHz

Electronics Design Laboratory 7

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

ECEN 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 pulses.

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

Group A Transmission

Group B Transmission RF Noise

Total RF noise and signal

Electronics Design Laboratory 8

RF Communication

ECEN 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

Electronics Design Laboratory 9

RF Communication

ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

• 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

Electronics Design Laboratory 10

RF Communication

ECEN 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+fm1 fc-fm1

Electronics Design Laboratory 11

RF Communication

ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

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

Electronics Design Laboratory 12

RF Communication

ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

fc+fm2 fc-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

Electronics Design Laboratory 13

RF Communication

ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

fc 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

Electronics Design Laboratory 14

RF Communication

ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

fc fc

• An RF receiver acts as a demodulator

• This demodulation shifts the frequency spectrum such that fc = 10kHz is shifted to 0Hz

• Both Group A and Group B receivers are picking up everything

fm1 fm2

Electronics Design Laboratory 15

RF Communication

ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

fc fc fm1 fm2

• An RF receiver acts as a demodulator

• This demodulation shifts the frequency spectrum such that fc = 10kHz is shifted to 0Hz

• Both Group A and Group B receivers are picking up everything

Electronics Design Laboratory 16

RF Communication

ECEN 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

2

10nF

10nF

R3

R1

R23

fm1 fm2

Group A Filtered Output

Group B Filtered Output

Electronics Design Laboratory 17

RF Communication

ECEN 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

2

10nF

10nF

R3

R1

R23

Group A Filtered Output

Group B Filtered Output

fm1 fm2

Electronics Design Laboratory 18

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

ECEN 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

1

10nF

10nF

R3

R1

R22

Group A Filtered Output

Group B Filtered Output

Electronics Design Laboratory 19

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

ECEN 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 Output

20ECEN 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

21ECEN 2270

Input Signal Transmitter Receiver Robot

(Arduino)Modulator Filter Peak Detector

RF Communication

Electronics Design Laboratory

5VDC

5VDC47kΩ

47kΩ 0.1μF

Input

10nF

R3

R1

R2

Peak Detector

5VDC

5VDC

R40.1μFR5

Comparator

Output

• Output is time delayed• Output pulses are shorter than input pulses!• There may be ‘bounce’ on positive transitions

Electronics Design Laboratory 22

Project• Must rely on fully functional Lab 2-5 circuits– Can re-do wireless or replace it with a different control

method if desired– Your robot does not need a remote control! (ex. line

followers and Roombas don’t need remotes)

• Must include an additional analog circuit-design hardware component. Programming only add-ons or enhancements do not count.

• When selecting components check– Range– Voltage– Communication

ECEN 2270

Electronics Design Laboratory 23

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

ECEN 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