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Kategorie: Diplomové, bakalářské práce |
Tento dokument chci!
Práce popisuje principy a problémy při realizaci ultrazvukového anemometru. Je popsán princip výpočtu rychlosti větru a následné korekce výpočtu. Pro realizaci jsou využity ultrazvukové sensory a microcontrolér ARM Cortex-M3. Práce se zabývá generováním PWM signálu, jeho analogovou filtrací, zesílením a odvysíláním. Na přijímací straně jeto nízkonapěťový zesilovač a komparátor. Vyvíjený kód je popsán pomocí vývojového diagramu.
Our PWM signal square wave signal with component 1,65 DC
component not suitable for usage with symmetrical power supplied amplifier.
Square wave signal composed from many harmonic components. That’s amplification. TR
and are rising and falling edge width. These values amplify signal by
28.
3. So
we would like eliminate 120 kHz, 200 kHz and higher harmonic components. PER period the generating signal and its width, both μs. For
this purpose was designed second order low pass filter. Another ones are odd multiple the first one.2 PWM filter and amplifier
Signal from PWM generator has high level 3,3 and low use whole
potential transmitter have adjust this PWM signal obtain kHz harmonic
signal with amplitude peak peak. set amplification
with resistor and 80kΩ feedback resistor R2.
14
.
For amplification used operational amplifier TL071 Texas Instruments. Cutoff frequency with
capacitor and resistor 470 33,9 kHz. Lower frequencies will attenuated. Used filter has dual
attenuation. That’s per octave, the third harmonic component will be
attenuated [7].Temperature sensor used correct airspeed reach better precision calculated
wind speed. Instead evaluation board PWM
generator takes place artificial pulse generator. For
elimination component was chosen high pass filter. This was created Pspice
software Orcad for the purposes simulation.
Slew rate V/μs and permit amplify frequencies till MHz [6]. will use
symmetrical power supply with non-inverting connection.
We can see connection this circuit image below. Used capacitor has nF
and resistor 390 This values shift cutoff frequency 40,8 kHz. It’s
commonly using low noise power amplifier with power supply voltage till ±18 [6]. and volts set low and high
level pulse. First harmonic
component frequency kHz. Results measurements and calculation wind speed are printed the
TI evaluation board built Screen
