Project #4: Build a whimsical, sort-of-public art installation #
System requirements #
- It should consist of at least one sensor and at least one actuator that are not attached to each other.
- The sensor and actuator should communicate with each other through the internet.
- The system should do something beautiful, intriguing, or both, without physical intervention or control signals from you.
- The system should be enclosed and repel a test finger probe, like that used in UL/IEC 60950-1. The idea here is that you should try to give your system a finished appearance, with no holes where people can stick their fingers in.
- To the extent that this is possible, the system should be installed in public location, because the world needs more joy in the dark winter coming up. If you live by yourself on a dead-end street with no foot traffic, “public” to your cat is okay.
Sensor requirements #
- It should sense something. It should not be a simple binary sensor, i.e. not just a pushbutton.
- The sensor hardware should filter the raw sensor data so the readings reported to the actuator are smooth.
- It should run without a connection to a laptop. Batteries or a wall plug are okay.
Actuator requirements #
- It should physically move in response to your sensor.
- Including LEDs, displays, or sound is also good, but not required.
- It should query your sensor via HTTP.
- It should run without a connection to a laptop. Batteries or a wall plug are okay.
If you are working in a team, while it is probably wise to have one of you manage the sensor and one of you manage the actuator, you are both responsible for the entire system. Saying, “Well, my side works; it’s his side that doesn’t work,” is the same as saying, “I have failed to get half of the project working.” Both sides are your sides.
Milestone 1: Build a mock-up: Wednesday, November 18, 11:59 PM
Final due date: Wednesday, December 2, 11:59 PM
More details for project #4 #
- If you need parts (like a sensor or a certain kind of motor), we’re happy to order them for you.
- See the Raspberry Pi setup page to learn how to control your Pi via serial cable and the Internet.
- See the Servers and Clients page for resources on coding your Pi and Arduino to send and receive data through the Internet.
- See the client and server setup demo video that walks through the code for Raspberry Pis and Arduinos as clients and servers
- See the Internet page to find out how IP addresses work.
Teaming options for project #4 #
Project 4 requires an internet-connected sensor that can send data in response to a request from an internet-connected actuator. Due to internet firewalls, this communication is only possible when either (1) both the sensor and actuator are on the same wireless network (i.e., Tufts_Wireless, or the same home wireless router), or (2) the sensor operator has access to change the firewall settings of their wireless router (specifically, the port forwarding settings). You may have heard of people doing this to run an Xbox; it’s the same situation, but just one port.
Option 1 – Work by yourself You’ll need to use both your Raspberry Pi and your Arduino, both connected to the same wireless network. With this approach, an individual student can satisfy the project requirement to include a sensor and an actuator that are not physically connected to each other and that communicate through the internet.
Option 2 – Work with a partner of your choice For this set-up to be successful, one of the following statements should be true:
- Both partners can access the Tufts campus network when testing and running your system, OR
- at least one partner (who operates the sensor node) has access to change the firewall (port forwarding) settings on their home wireless router, OR
- both partners are willing to work patiently with the ME 30 team on creating an encrypted tunnel through your firewall.
Be sure to ask any potential partners about their wireless situation both before and after Thanksgiving. The project is due on Dec. 1.
Option 3 – Work with a partner assigned to you by Kristen and Brandon We’ll pool all the people who would like to be assigned a partner, and make optimal pairs based on your responses to the following questions about wireless network access.
- Will you have access to the Tufts campus wireless network both before and after Thanksgiving?
- Do you have access to change the firewall (port forwarding) settings of your home wireless router?
Project #3: Build an electromechanical game #
Your task is to build a game with the following characteristics:
- It is controlled by a microcontroller like an Arduino or Raspberry Pi. (Choose the Arduino unless you’re a Pi zealot.)
- It has at least one electromechanical element that moves, like a motor or a solenoid.
- It has some kind of user input, like buttons, knobs, joysticks, sensors, or the like.
- It is at least sort of fun to play. A blinking LED is not a game.
- (It does not need to have a custom PCB, but it can if you want. If it has a custom PCB, you must make a working prototype first.)
Midway milestone: Build a prototype: Wednesday, October 21, 11:59 PM
Final due date: Monday, November 2, 11:59 PM
Plan to demo your playable game in pods on November 3rd and 5th.
More details for project #3 #
If you need parts (like a sensor or a certain kind of motor), we’re happy to order them for you.
Project #2: Build an H-bridge motor controller #
The second project is to build a motor controller with the following characteristics:
- It consists of a PCB with screw terminals for power and control lines.
- It also accepts power from a 2.1 x 5.5 mm plug from a 12 V wall adapter.
- It has a power LED that lights up when motor power is available.
- It can make a DC motor spin in both directions.
- The motor current traces can handle 12 V and 5 A continuously without melting.
- It can be controlled by logic signals from an Arduino (but later, not as part of what you submit for P2).
Due date for prototype: Wednesday, September 30, 11:59 PM
To get started building your prototype H-bridge, review the Low Power/high power and the H-bridge(http://andnowforelectronics.com/notes/h-bridge/) pages, including their mini-lecture videos on BJT and MOSFET transistors. After that, if you’re stuck, consult the H-bridge testing demo video. Note that this video is not intended to give you step-by-step building or testing instructions, but rather to give you a feel for the kind of approach you might take to building and testing this circuit. If your H-bridge prototype isn’t working by the deadline for this prototype, don’t worry! Just submit to Canvas a photo of what you have, working or not.
Due date for PCB submission: Wednesday, October 7, 11:59 PM
When your design is ready, you should submit it to the fabricator, OSH Park. It will cost you around $10. After you submit it, take a screenshot of your order confirmation and upload it to the Project 2 PCB assignment on Canvas. That will serve as proof that you submitted your project on time.
Project #1: Build a breadboard power supply #
The first project is to build a power supply with the following characteristics:
- It consists of a PCB that plugs directly into a breadboard.
- It accepts power from a 2.1 x 5.5 mm plug from a 12 V wall adapter.
- It emits 12 V, 5 V, and 3.3 V (at the same time).
Due date (for PCB submission): Wednesday, September 16, 11:59 PM
When your design is ready, you should submit it to the fabricator, OSH Park. It will cost you around $10. After you submit it, take a screenshot of your order confirmation and upload it to the Project 1 PCB assignment on Canvas. That will serve as proof that you submitted your project on time.
More details for project #1 #
First of all, we’re not trying to build anything revolutionary in this project. None of you have ever made a PCB before, so the point is to make something fairly simple to get comfortable with the process. If you search Amazon for “breadboard power supply”, you’ll see that you can buy various versions of things like this, though none with a 12 V passthrough, so far as I’m aware.
Here’s what a typical one of these things looks like.
The image below shows the rough mechanical constraints for the PCB. You can make a board of whatever dimensions you want, but it needs to plug into the breadboard, so you probably want to follow the pin location dimensions shown below. You don’t have to have pins where all of the 8 red dots are– you could get by with just 4, but 8 will make the board stay in place a little more securely.
In your project kit, you’ll find all the components you’ll need to build a prototype of your power supply on a breadboard. You build the prototype and make sure that you’ve got the wiring right. Then, make the PCB with the same connections. Finally, when your PCB arrives in the mail, you can reuse the prototype components on your PCB.
Important note #1: the pins on the two regulators are not in the same order!
Check the datasheets for the components to see which pin is the input pin, which is the output pin, and which should connect to ground.
Important note #2: the pins on the power jack are weird! More details below.
There’s a cryptic diagram in the datasheet for the PJ-102AH power jack, shown below.
One part is obvious: the pin in the middle is connected to pin 1.
But what is that little arrow/bump thing with pins 2 and 3?
That’s trying to tell you that when the jack is empty (i.e. no plug inserted), pins 2 and 3 are connected together. When you insert the plug, the barrel pushes on the bump at the end of the pin 2 contact, which bends it away from the pin 3 arrow, breaking the connection to pin 3. It’s so that you can detect whether there’s a plug inserted or not, which can be useful for battery-powered systems. You don’t need to implement that feature on your regulator board.