ENGG1015: Project Circuits

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1 : The Big Picture 1 st Semester (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 3 Times... Set DONE Light Tracking Laser Head Laser Shoot On Target POP DONE Laser On Some time later... Final Step Start Ball Popper Light Ball Popper Light On 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: 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 JA JB JC Description Connect to Ball Counting Tunnel via the breadboard Connect to DAC module, then to the breadboard Connect to ADC module, then to the breadboard

2 On the breadboard there will be circuits from Lab 8 as well as a new connection that connect from JA of the FPGA board to the tunnel and the laser head. See next section. 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 main connections for this part: 1. Detect the passing of a ball using the photodetector in the tunnel. The information is sent to the FPGA to trigger the counting state machine; 2. When 3 balls have been detected, the FPGA asserts a done signal. This done signal should then 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 correctly trigger the final ball popper. 3.1 Connecting to the Tunnel The connection between the tunnel and the FPGA is the same as that from Lab 4. Similar to the case of Lab 4, you should use a potentiometer to implement the 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 connection at JA: Pin Connection Description 6 din 1 when a ball passes through the tunnel, 0 otherwise 5 Not connected 4 done Stay at 1 after 3 balls have been detected, 0 otherwise. 3 Not connected 2 GND Ground 1 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 with a voltage of 3.3V, while a logical LOW signal is represented with a voltage of 0V. However, the output pin of the FPGA cannot provide enough current to make a bright laser. As a result, we will 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 in Figure 3. V cc = 12V done + L + Figure 3: A voltage follower to drive laser module of the light tracker. Page 2 of 5

3 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. Vdd = 3.3V To JA of FPGA Pin 1 4 To Tunnel To L+ of Light Tracker Vcc = 12V Figure 4: Breadboard connection for voltage follower that acts as a buffer to the laser module. 4 Light Tracker The light tracking laser head is going to serve as the final machinery to pop the balloon in the grand 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, and that 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 can test your circuit using a simple hand torch. In addition, you need to activate the light source of the 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 a circular arc. Page 3 of 5

4 ENGG1015 Figure 5: A Ball Popper NOTE: You do not need to construct the balloon popper. It is made for you by the ENGG1015 staff. 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 serves both as an indicator that it is powered and as a way to align your light tracker. If your light tracker is working properly, it should be pointing exactly to the center of the arc at this time. 2. Subsequently, you must activate the moving light pattern of the popper by asserting a lighton signal to the popper. With lighton at 12V, the lights on the arc will start to move in a random pattern. Your light tracker head must be able to track this movement correctly. 3. In addition, the light sensor corresponding to the light source will be activated. If your light tracker can correctly track the moving light AND your laser is turned on, then you will be able to shoot right on the activated sensor with your laser. With the sensor shot by 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 inserted into custom made slots right in the middle of the ball popper. Your job is to make sure that your light tracker is securely connected to the breadboard, and is easily accessible near the edge of your machine so it can be inserted into the popper. 4.3 Interfacing to the Popper Electrical Your machine should assert the lighton signal as the final step. The lighton signal has the simple definition: Voltage 12V 0V Description Turn on the random light pattern Do not turn on random light patter For ease of connection, securely connect the lighton signal and ground to a terminal block similar to the one shown below. Figure 6: User a terminal block to connect lighton signal. Page 4 of 5

5 4.4 Buffering lighton Signal To make your design easier, a solid-state relay (SS-RELAY) will be used on the balloon popper to receive your lighton signal. Therefore, simply make sure your lighton signal can deliver at least 12mA when under 1kΩ resistive load. Good luck & Enjoy! Page 5 of 5