Kart/sensors/HCSR04
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− | == | + | == Ultrasound ranger == |
− | The | + | The [http://www.elecfreaks.com elecfreaks] |
− | + | [http://www.elecfreaks.com/store/hcsr04-ultrasonic-sensor-distance-measuring-module-ultra01-p-91.html Ultrasonic sensor distance measuring module] | |
− | + | receives a trigger pulse, <code>startMeasure</code>, sends an ultrasonic pulse train | |
− | + | and then provides a pulse, <code>distancePulse</code>, whose length is proportional to the sound flight and echo time. | |
− | + | ||
− | + | [[File:Ultrasound ranger.svg|center|500px]] | |
− | | | + | |
− | | | + | It has a dedicated [[Kart/sensor board#Ultrasound ranger|connector]] on the [[Kart/sensor board|I/O board]]. |
− | + | ||
− | | | + | The <code>ultrasoundRanger</code> block in the <code>sensors</code> FPGA counts the ultrasonic pulse length in terms of the 10 MHz clock periods. |
− | | | + | The distance is thus given by: |
− | + | ||
− | + | :: <math>distance = count \cdot 0.0017 ~ [cm]</math> | |
− | + | ||
− | + | There is approximately 500 us between the trigger and the start of the answer. | |
− | + | Moreover, for ranges of about 20-30 cm, the return signal duration is of an order of 2 ms. | |
− | + | Thus, a measurement cycle should take at least something like 10 ms, achieving a maximal measurement rate of about 100Hz. | |
− | + | ||
− | + | ||
[[Category:Kart]] | [[Category:Kart]] |
Latest revision as of 09:19, 24 August 2016
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Ultrasound ranger
The elecfreaks
Ultrasonic sensor distance measuring module
receives a trigger pulse, startMeasure
, sends an ultrasonic pulse train
and then provides a pulse, distancePulse
, whose length is proportional to the sound flight and echo time.
It has a dedicated connector on the I/O board.
The ultrasoundRanger
block in the sensors
FPGA counts the ultrasonic pulse length in terms of the 10 MHz clock periods.
The distance is thus given by:
There is approximately 500 us between the trigger and the start of the answer. Moreover, for ranges of about 20-30 cm, the return signal duration is of an order of 2 ms. Thus, a measurement cycle should take at least something like 10 ms, achieving a maximal measurement rate of about 100Hz.