ENGG1015: Project Circuits The Big Picture 1 st Semester 2012-13 (v1.0) ...................................................................... 1 Overview This document summarizes the circuit that you need to construct in order to interface with the required steps, namely, the ball counting tunnel and the final light tracker. It is intended to serve as a guide for you to construct the circuits for the final project. Some of the materials are directly from previous labs and you should refer to them as appropriate. Note that some of the circuits are new. It means you will have to build these circuits on your own without any “lab checkoff”. The conceptual overview of the required connection is repeated here: Ball Counter Light Tracking Laser Head Ball Popper Light On Laser On DONE 3 Times... Set DONE Start Ball Popper Light Final Step Laser Shoot On Target P O P Some time later... Figure 1: Overview of connections between required stages. ...................................................................... 2 FPGA Design A template of the final design that you should implement on the FPGA is provided here: http://www.eee.hku.hk/ ~ engg1015/fa12/labs/proj1015.zip In short, this design combines the ball counting state machine you have developed in Lab 3 & 4 and the proportional controller in Lab 8 into the same design. The .ucf file has been updated so the FPGA may correctly connect to the external circuits on the breadboard using the I/O ports. There are 3 external connections to the FPGA as follows: Connector Description JA Connect to Ball Counting Tunnel via the breadboard JB Connect to DAC module, then to the breadboard JC Connect to ADC module, then to the breadboard
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ENGG1015: Project Circuits
The Big Picture
1st Semester 2012-13 (v1.0)
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1 Overview
This document summarizes the circuit that you need to construct in order to interface with therequired steps, namely, the ball counting tunnel and the final light tracker. It is intended toserve as a guide for you to construct the circuits for the final project. Some of the materials aredirectly from previous labs and you should refer to them as appropriate. Note that some of thecircuits are new. It means you will have to build these circuits on your own without any “labcheckoff”.
The conceptual overview of the required connection is repeated here:
BallCounter
Light TrackingLaser Head
Ball PopperLight On
Laser OnDONE
3 Times...
Set
DO
NE
Start BallPopper Light
Final Step
Laser ShootOn Target
POP
Some time later...
Figure 1: Overview of connections between required stages.
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2 FPGA Design
A template of the final design that you should implement on the FPGA is provided here:
http://www.eee.hku.hk/~engg1015/fa12/labs/proj1015.zip
In short, this design combines the ball counting state machine you have developed in Lab 3 & 4and the proportional controller in Lab 8 into the same design. The .ucf file has been updatedso the FPGA may correctly connect to the external circuits on the breadboard using the I/Oports. There are 3 external connections to the FPGA as follows:
Connector DescriptionJA Connect to Ball Counting Tunnel via the breadboardJB Connect to DAC module, then to the breadboardJC Connect to ADC module, then to the breadboard
ENGG1015 Project Circuits
On the breadboard there will be circuits from Lab 8 as well as a new connection that connectfrom JA of the FPGA board to the tunnel and the laser head. See next section.
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3 Connection to Ball Counting Tunnel
A large part of this design is from Lab 3 and 4. You should refer to them. There are two mainconnections for this part:
1. Detect the passing of a ball using the photodetector in the tunnel. The information is sentto the FPGA to trigger the counting state machine;
2. When 3 balls have been detected, the FPGA asserts a done signal. This done signal shouldthen turn on the laser in the light tracker.
The first connection above is identical to that from Lab 4, please refer to the connection there.The second connection is new and you will need to construct it for your project to correctlytrigger the final ball popper.
3.1 Connecting to the Tunnel The connection between the tunnel and the FPGA is the sameas that from Lab 4. Similar to the case of Lab 4, you should use a potentiometer to implementthe pull-up resistor.
WARNING: you should only connect 3.3V to L+ and ground to L− of the tunnel. Applying
voltage higher than 3.3V to the laser module will cause permanent damage.
3.2 Turning on Laser The done signal from the FPGA is connected to pin “J3” of the FPGA,which translate to Pin 4 of the connector JA. The following table summarizes the connectionat JA:
Pin Connection Description6 din ‘1’ when a ball passes through the tunnel, ‘0’ otherwise5 – Not connected4 done Stay at ‘1’ after 3 balls have been detected, ‘0’ otherwise.3 – Not connected2 GND Ground1 VCC 3.3V – connect to the top “+” row on breadboard only.
Figure 2: Connection on JA of FPGA board.
3.3 From lab, you already know that a logical HIGH signal on the FPGA is represented witha voltage of 3.3V, while a logical LOW signal is represented with a voltage of 0V. However, theoutput pin of the FPGA cannot provide enough current to make a bright laser. As a result, wewill need to buffer the done signal similar to the way we buffer the signals that drive the motor.
We will use a voltage follower circuit to drive the laser from the FPGA board as shown inFigure 3.
−
+
Vcc = 12V
L+done
Figure 3: A voltage follower to drive laser module of the light tracker.
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ENGG1015 Project Circuits
3.4 Check Yourself Ask yourself the following questions:
• What are the input voltages at done when it is HIGH/LOW?
• What are the output voltages at L+ when done is HIGH/LOW?
• Why is the op-amp powered by 12V instead of 3.3V?
3.5 Breadboard Connection You need to use an additional op-amp IC for this buffer circuit.A template for constructing the voltage follower on the breadboard is shown in Figure 4.
10
35
40
45
50
55
10
35
40
45
50
55
1 2 3 4
6 58 7
Pin 1To JA of FPGA
Vdd = 3.3V
Vcc = 12V
To L+ ofLight Tracker
To Tunnel
Figure 4: Breadboard connection for voltage follower that acts as a buffer to the laser module.
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4 Light Tracker
The light tracking laser head is going to serve as the final machinery to pop the balloon in thegrand finale. It is therefore very important for you to make sure it works properly.
There are two steps to a successful popping of balloon:
1. Laser on the tracking head must be turned on.
2. The head must be able to track a light source and point straight into the light source.
For Step 1 above, you have to make sure the done signal is correctly turned on after 3 balls, andthat the buffer circuit in Part 3.3 is properly functioning.
For Step 2 above, there are 2 subtasks that must be simultaneously functioning correctly. First,you will need to make sure the tracking mechanism from Lab 7 & 8 is working properly. You cantest your circuit using a simple hand torch. In addition, you need to activate the light source ofthe balloon popper that is provided by your TAs.
4.1 Balloon Popper The balloon popper is a special apparatus built for the project this year.As can be seen from Figure 5, it has an array of light sources and sensors in the shape of acircular arc.
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ENGG1015 Project Circuits
Figure 5: A Ball Popper
NOTE: You do not need to construct the balloon popper. It is made for you by the ENGG1015staff. Your task is to make sure your Rube Goldberg machine can interface to it correctly
during the final competition.
The balloon popper works as follows:
1. When powered on, the light in the center of the arc will light up constantly. This servesboth as an indicator that it is powered and as a way to align your light tracker. If yourlight tracker is working properly, it should be pointing exactly to the center of the arc atthis time.
2. Subsequently, you must activate the moving light pattern of the popper by asserting alighton signal to the popper. With lighton at 12V, the lights on the arc will startto move in a random pattern. Your light tracker head must be able to track thismovement correctly.
3. In addition, the light sensor corresponding to the light source will be activated. If yourlight tracker can correctly track the moving light AND your laser is turned on, then youwill be able to shoot right on the activated sensor with your laser. With the sensor shotby a laser, it will activate a pump that eventually will pop a balloon.
4.2 Interfacing to the Popper – Mechanical Your Light Tracking Laser Head will be insertedinto custom made slots right in the middle of the ball popper. Your job is to make sure that yourlight tracker is securely connected to the breadboard, and is easily accessible near the edge ofyour machine so it can be inserted into the popper.
4.3 Interfacing to the Popper – Electrical Your machine should assert the lighton signal asthe final step. The lighton signal has the simple definition:
Voltage Description12V Turn on the random light pattern0V Do not turn on random light patter
For ease of connection, securely connect the lighton signal and ground to a terminal blocksimilar to the one shown below.
Figure 6: User a terminal block to connect lighton signal.
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ENGG1015 Project Circuits
4.4 Buffering lighton Signal To make your design easier, a solid-state relay (SS-RELAY) willbe used on the balloon popper to receive your lighton signal. Therefore, simply make sure yourlighton signal can deliver at least 12mA when under 1kΩ resistive load.
Good luck & Enjoy!
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