Kart/sensor board
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(→Ultrasound ranger) |
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=== Ultrasound ranger === | === Ultrasound ranger === | ||
− | The | + | The [[Kart/sensors/HCSR04|ultrasound ranger]] connectors are located on the side of the I/O board's middle row. |
It is the single 5-pin connector. | It is the single 5-pin connector. | ||
The sensor cable is to be connected as: | The sensor cable is to be connected as: |
Revision as of 08:40, 21 August 2015
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The sensor board provides different I/Os to the system. The schematics provides detailed information about it.
Inputs and outputs
End of turn switch
The end of turn switch is located in the I/O board's middle row. It is the 4-pin connector closest to the 5-pin connector. The switch cable is to be connected as:
cable pin green 5 V power supply yellow input
The input has a pull-down resistor. Closing the switch brings a logic '1'.
Hall sensors
The sensor connectors are located in the I/O board's middle row. The sensor cable is to be connected as:
cable pin red 3.3 V or 5 V power supply brown sensor signal black ground
Ultrasound ranger
The ultrasound ranger connectors are located on the side of the I/O board's middle row. It is the single 5-pin connector. The sensor cable is to be connected as:
cable pin red 5 V power supply yellow measurement start (trig) green distance signal (echo, in) black ground
Proximity sensors
The proximity sensor connectors are located in the I/O board's side row.
The sensor cable is to be connected as:
cable pin orange 3.3 V power supply yellow SDA green SCL blue ground
LED outputs
The board has 4 LED outputs which can also be used for other purposes, such as buzzers.
The outputs have a common power supply, 2 resistor mount holes and a 2-pin LED connector located on the I/O board's bottom row.
The power supply is connected directly to the 12 V battery packs. The resistor is connected between the power supply and the LED. The LED is connected between the resistor and the ground.
FPGA design
One or two Hall sensors are used to track the distance driven by the kart. An ultrasound ranger can detect if there is an obstacle at the front of the kart.
To begin with, the design environment has to be downloaded.
It comprises the sensorsInterface
block which contains the provided I2C bus interface,
an empty hallCounters
block
and an empty ultrasoundRanger
block which are to be designed.
Hall sensor
The hall sensor has a Schmitt-trigger output. This means that it has to "see" a north and then a south magnetic pole in order to switch its output.
The block receives a hallPulses
signal array, one per hall pulse sensor.
For each of these inputs, it requires a counter.
The counter values are concatenated to build the position
output.
Ultrasound ranger
The ultrasound ranger receives a trigger signal, startMeasure
, and sends an ultrasound pulse.
Once the pulse is sent, the sensor drives distancePulse
to '1' as long as it hasn't received any echo.
The circuit has to count the length of the sequence in terms of clock pulses and returns the value on distance
.