QTR-8RCReflectance Sensor Array:

Line sensingTeam: Grounded

Rachel Kmetz, Matthew Forsyth, Austin Meirick, and Levi Eisel

What is the problem?

Line Sensing

What are we not doing?

-Steering-Speed-Noise-Tracking

QTR-8RC

Physical Overview:QTR-8RC

Each module carries eight IR emitters and receivers.

Outputs are all independent

The LEDs are controlled by MOSFET, that are normally pulled high.

Operational Voltage: 3.3 – 5.0V

Supply current is 100mA Note: The optimal

sensing for the QTR-8RC is 0.125” about 3mm. The QTR-8RC can NOT be placed to close nor to far from the black line this could warp data.

The maximum sensing distance is around .374” about 9.5mm.

Physical Characteristics

The same pins appear in different locations but you don’t have to connect to all of them.

Vcc and GND are where the sensor gets power. Vcc must be between 3.3-5v.

IR LEDs achieve optimal brightness at 5v.

LEDON is connected to the MOSFET and gives power to the IR LEDs. When this pin is high, all the LEDs are on.

Components Needed16-Conductor Ribbon Cable:You will use this to connect from the QTR-8RC to the 16-pin Ribbon cable-to- breadboard Adapter.

• IR Array Mounting Bracket : Mounts the QTR-8RC to the “SmartCar”• 16-pin Ribbon cable-to-Breadboard Adapter• Items used in mounting. • QTR-8RC: Our reflectance sensor array that are intended for line sensing.

HardwareBelow is pictures and commentary about how to mount the QTR-8RC to your “SmartCar”

Figure 1: View from the front of the car.

•Figure2: You need to place the IR mounting bracket on the front of the car. From the IR bracket you need to add spacers and secure them to both the IR bracket and the QTR-8RC. •These spacers will get the QTR-8RC to the correct height above the line. •You have now mounted your QTR-8RC

Electrical

Connect 5volts and ground from ColdFire to the ribbon cable adaptor. Make sure you check continuity of the ribbon cable to the QTR-8RC before you connect the 5 Volts.

You then need to map your ports from the ribbon cable to the QTR-8RC and the 8 bit output port, such as port B or E.

Output from Line Sensing

QTR-8RC BLACK LINE

QTR-8RCWHITE SPACE

Note: This is when all 8 of the IR Receivers are over top of either the while space or the back line.

Output from Line Sensing

This is the oscilloscope print out of the QTR-8RC over the black line and some white space. Look at how lines 8,9,13,14,15 are significantly lower than lines 11,12. This is because those lines are over the white space, unlike lines 11,12 they are the black line.

Software Drive the I/O line high and make it an output. Allow 10us for the capacitors to charge. Make the I/O line high Impedance (an input) Wait for the I/O line to go low, then measure

how long it takes for the capacitor to discharge.

Sites and Resouces

 Qtr-8A And Qtr-8Rc Reflectance Sensor Array User's Guide, and © 2001–2009 Pololu Corporat. Pololu - QTR-8A and QTR-8RC Reflectance Sensor Array User's Guide (n.d.): n. pag. Web

Pololu Qtr Reflectance Sensor Application Note, and © 2001–2009 Pololu Corporat. Pololu - Pololu QTR Reflectance Sensor Application Note(n.d.): n. pag. Web.

Thank you!