Week 13 Today

1. Week 13Today • Homework presentations. • Data to and from with LEDs. • H-bridge, Batteries and such. • Final project discussion.

2. Homework • Present inspirations. • Show your FUNCTIONAL interactive piece. • Show documentation of your other draft piece. • Discuss your concept.

3. Review and Requests

4. Arduino PWM • Arduino has built-in PWM • On pins 9,10,11 • Use analogWrite(pin,value) • It operates at a high, fixed frequency(thus not usable for servos) • Great for LEDs and motors • Uses built-in PWM circuits of the ATmega8 chip (no software needed) • Why do we need software PWM sometimes? • PWM speed used for analogWrite() is set to 30 kHz. • When programming PWM, speed can be set to just about any value. Src: Tod E Kurt

5. Color PWM Three PWM outputs and three primary colors - sounds interesting doesn’t it? With RGB, you can make any color…. Use either the 220 or 330 ohm resistors Src: Tod E Kurt

6. Dimming LEDs To make a cool color dimmer - http://www.arduino.cc/en/Tutorial/DimmingLEDs (that’s the code you’ll need) You’ll basically be fading nicely through a lot of colors. Src: Tod E Kurt

7. Mood Diffuser To make something a bit more interesting…. Face your project with some semi-transparent material - like this scratched acrylic. Src: Tod E Kurt

8. Working with more than 5v Your board runs on 5 volt logic. This means all the signals are between 0-5 volts. Also that you can burn out your components if you run more than 5 volts through them. But - lots of things run on higher voltage.. because they’ll have more power to do work for you. So you need something that you can control with 5 volt logic that can send information (or current) at a higher voltage. It’s called an h-bridge. There are many of them.

9. An H-Bridge example • There are many h-bridges… you’ll need to find one that works for your project • How much power do I need? • How many do I need in one chip? • Etc. • We’ll work on an example for a low-voltage DC motor (5-36v) that you can send forward and in reverse. • This example uses an H-bridge IC, the Texas Instruments SN754410 (or the L293). This chip has 4 half-H bridges, and can therefore control 2 motors. It can drive up to 1 amp of current, and between 4.5 and 36V. If your motor needs more than that, use a different H-bridge. Ref: http://tigoe.net/pcomp/labs/lab-motors.shtml

10. About H-bridges • All H-bridges have certain elements: • Pins for logic input • Pins for Supply voltage • Pins for Logic voltage • Pins for Supply output • Pins for ground • The logic voltage pins want the same voltage and current as your microcontroller. • The supply voltage wants whatever voltage and current you run your motors with. • The logic inputs connect to the pins on your microcontroller that you use to output control signals to the H-bridge. • The supply output pins go to your motor. • The configuration of these pins might vary slightly depending on the manufacturer of the H-bridge. They might also use slightly different names, but the concepts are the same. Ref: http://tigoe.net/pcomp/labs/lab-motors.shtml

11. Getting one working… Step 1: Test your motor!! You need to know it works before you start so that if there is a problem you know it’s not with the motor. Get a DC motor that runs on low voltage DC, in the 5-15V range. Connect leads to its terminals, and run it from a DC power supply. Try changing the voltage on it, and seeing what effect it has. Don't go over the motor's rated voltage. Connect a switch in series with the motor and use it to turn on the motor. Ref: http://tigoe.net/pcomp/labs/lab-motors.shtml

12. Start on the H-bridge Step 2: Set up the chip Connect things carefully. You’ll need: SN754410 (or L293) H-bridge DC motor power supply for DC motor 5-15vdc power supply 10uF capacitor 1uF capacitor 10Kohm resistors 220 ohm resistors 5 volt regulator (7805) Image shows H-Bridge connected to a PIC. Note the motor supply wire. In this example, it runs to the 12V input from the DC power supply, because the motor runs on 12V. It may be different on your circuit, depending on the voltage your motor needs. Note also the 10Kphm pull down resistor needed on the enable pin. Ref: http://tigoe.net/pcomp/labs/lab-motors.shtml

13. Double check. Step 2a: Double check. Really.

14. Set up the power. Step 3: Get the power set so that it runs the correct voltages to the correct places. Most motors take much more current than a microcontorller, and need their own supply. This example uses 12V, run in parallel with a 7805 5v regulator. Whatever motor you use, make sure the power source is compatible (i.e. don't use a 9V battery for a 3V motor!). Note that we've added two capacitors on either side of our regulator. They smooth out the power, as the motor will cause spikes and dips when it turns on and off. Here's the schematic for the capacitors and the regulator. Note that the motor and the microcontroller need a common ground (in our case, they get it through the transistor's base; see above schematic). Ref: http://tigoe.net/pcomp/labs/lab-motors.shtml

15. Set up your program. Step 4: Program your arduino board. (I have not tested) Wiring Code (for Arduino board): /* DC motor control by Ryan Holsopple modification of Tom Igoe's DC motor code I added function to start motor turning in one direction I raised the threshold for my pot to work Created 8 Feb. 2006 */ int sensorValue = 0; // the variable to hold the analog sensor value int sensorPin = 0; // the analog pin with the sensor on it int motorPin = 9; // the digital pin with the motor on it int threshold = 300; // theshold of analog sensor below which the motor should turn on int forwardPin = 7; int backwardPin = 8; // prototype of the function that changes the motor's speed: void changeMotorSpeed(); //function to begin motor turning in one direction void forwardDirection(); void setup() { // declare the inputs and outputs: pinMode(motorPin, OUTPUT); pinMode(forwardPin, OUTPUT); pinMode(backwardPin, OUTPUT); pinMode(sensorPin, INPUT); } void loop() { // read the analog sensor sensorValue = analogRead(sensorPin); // determine whether its above or below the threshold if (sensorValue > threshold) { // it's above the threshold // turn off the motor digitalWrite(motorPin, LOW); } else { //start motor turning forward forwardDirection(); // change the speed of the motor based on the sensor value: changeMotorSpeed(); } } //////////////////////////////////////// void forwardDirection(){ digitalWrite (forwardPin, HIGH); digitalWrite (backwardPin, LOW); } void changeMotorSpeed() { analogWrite(motorPin, sensorValue); } http://itp.nyu.edu/physcomp/Tutorials/DC1L293HBridge

16. Running Arduino via battery. Great for portability. Bad for Reliability. With just two parts your Arduino goes portable, powered by a 9V battery. Step 1: You'll need a 9V battery clip, a 2.5mm power plug, a soldering iron and some solder, and optionally a small piece of heat shrink tubing. Step 2: Solder the battery clip's black (-) wire to the outside connection of the plug. Then, solder the battery clip's red (+) wire to the centre connection of the plug. Optionally, add a piece of heat shrink tubing on the red wire to protect the positive connection. http://www.arduino.cc/playground/Learning/9VBatteryAdapter

17. Running Arduino via battery. Great for portability. Bad for Reliability. Step 3: Once the wires are soldered, slip the heatshrink over the positive connection and gently crimp the wires in place with the small metal tabs. Add some hot glue (not shown) over the connection area for further reliability. http://www.arduino.cc/playground/Learning/9VBatteryAdapter

18. Break, 10 minutes.

19. Homework • Prepare your draft presentation site. • Presentation site must include documentation of your draft projects. • GROUP PROJECTS: Be sure to write what YOU did in the group project. • Revise and combine your interaction drafts completed for this week. • These must be functional in the next class. • DO NOT WAIT UNTIL THE NIGHT BEFORE to work on this. • Be ready to present your final draft of your final project to the class at next session. • All or most functionality working • Strong concept • Finished code, ready to implement feedback and suggestions • Clear questions to ask for help • Ready to start on the physical enclosure You should do most of your work on the final THIS week. So next week you only have to complete the physical enclosure, debug your work, and put together the final presentation.