Difference: TheUCCOpenDay (3 vs. 4)

Revision 42017-10-11 - uli

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META TOPICPARENT	name="WebHome"

The UCC open day

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The voltmeter uses an 8 bit ADC whose input is connected to a voltage coming from a potentiometer. If you turn the pot, the voltage will change and you will read another digital value from the ADC. The hexadecimal value read from the ADC is displayed on the LCD display together with the voltage. Since the values 0..0xff correspond to 0..Vcc (which is 3.3V) you can easily calculate the conversion.

The meteorological Station

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The meteorological station uses a DHT11 humidity and temperature sensor as well as a bmp180 temperature and barometric pressure sensor. Both sensors are read out ever 60 seconds. The DHT11 has the problem that the data read from it may be corrupted because if incoming interrupts which inhibit the readout of the device while it is sending data. A checksum allows to recognize this problem in which case the measurement and readout is simply repeated. You must wait at least 2 s however because the DHT11 needs this time to be ready for the next measurement.

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The meteorological station uses a DHT11 humidity and temperature sensor as well as a bmp180 temperature and barometric pressure sensor. Both sensors are read out ever 60 seconds. The DHT11 has the problem that the data read from it may be corrupted because if incoming interrupts, which inhibit the readout of the device while it is sending data. A checksum allows to recognize this problem in which case the measurement and readout is simply repeated. You must wait at least 2 s however because the DHT11 needs this time to be ready for the next measurement.

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A typical signal display is available

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A typical pulse train from the DHT11 is shown here:

The program to be run is in /opt/ucc/openday/meteo and is called meteo. The command ./meteo will run it. The program opens a file meteo.dat for data logging. I extracted the temperature, humidity and air pressure measured during the weekend and placed the original data meteo.dat and the extracted data temperature.dat, humidity.dat and pressure.dat into the logs subdirectory. In logs you will also find an executable gnuplot script to plot these data. ^C will exit this gnuplot script.

Uli Raich - 2017-10-06

Comments

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