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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.
For
elimination component was chosen high pass filter.
14
. Instead evaluation board PWM
generator takes place artificial pulse generator. It’s
commonly using low noise power amplifier with power supply voltage till ±18 [6]. For
this purpose was designed second order low pass filter.
Square wave signal composed from many harmonic components. Used filter has dual
attenuation. These values amplify signal by
28.
Slew rate V/μs and permit amplify frequencies till MHz [6].
3.
For amplification used operational amplifier TL071 Texas Instruments. Used capacitor has nF
and resistor 390 This values shift cutoff frequency 40,8 kHz.
We can see connection this circuit image below. PER period the generating signal and its width, both μs. Results measurements and calculation wind speed are printed the
TI evaluation board built Screen. and volts set low and high
level pulse.
Our PWM signal square wave signal with component 1,65 DC
component not suitable for usage with symmetrical power supplied amplifier. So
we would like eliminate 120 kHz, 200 kHz and higher harmonic components. First harmonic
component frequency kHz.Temperature sensor used correct airspeed reach better precision calculated
wind speed. This was created Pspice
software Orcad for the purposes simulation. will use
symmetrical power supply with non-inverting connection. Lower frequencies will attenuated.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. Another ones are odd multiple the first one. That’s amplification. set amplification
with resistor and 80kΩ feedback resistor R2. Cutoff frequency with
capacitor and resistor 470 33,9 kHz. TR
and are rising and falling edge width. That’s per octave, the third harmonic component will be
attenuated [7]
