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Weather Station

· Santosh on May 14 2008 09:24:01

Weather station with pressure reading, relative humidity, indoor & remote outdoor temperature display.Both Celsius or Fahrenheit & mbar/hPa or mm Hg supported. With calendar & clock. Easy 3-button user-menu. 42 hour-history display (curve). Auto-memory & display of all high and low-values. PIC 18F452 running at 4 MHz, power saving sleep mode. Sensors are only turned on when needed..

Circuit Explanation:

Now this was a huge project! All sensors had to be fully tested one at a time, wireless communication had to be perfect, various LCDs were tried. Nevertheless, here's the result: hope you enjoy it!

The circuit may be powered by a small 9V battery, but you'd better take a couple of AA-batteries. A 6-pack will last a several months. Consumption for the base station is around 8 to 9 mA whilst active and only 2 to 3 mA in sleep mode (LCD remains on.) The transmitter takes slightly less.

The receiver (base station) is active during 5 seconds & then goes to sleep for 45 seconds. The transmitter takes a nap every 30 seconds or so.

Menu mode is entered when pushing the "menu" button (what's in a name?) for 1 second. Browsing & value changes are done with the "min" & "plus" keys. When in normal mode (like in the picture above), the "min" and "plus" keys can browse through the different histories. All these controls will wake up the processor if it was in sleep mode.

On the left-hand side of the LCD we have (from top to bottom :) Outside temperature, Pressure, inside Temperature, Relative Humidity, Calendar and Clock.

On the right: High value of the past 42-hours, Bar graph histogram (right is most recent value), Low value.

All sensors are read & LCD (left-hand side) are updated every 50 seconds. Histogram is updated on the hour (e.g. 10h00, 17h00, 22h00,...). All data is stored in EEPROM and is loaded at power-up. In case of a power failure (or when changing batteries), there will be no data (nor history) lost.

MPX 4115A pressure sensor	Most expensive part of the project (around € 20,- / $ 25,-), but it's worth it. Output of this sensor is an analogue voltage, which is temperature-compensated! We'll feed this directly to the PIC's 10-bit ADC.
TC77 SPI temperature sensor	Nice SPI-sensor in a tiny SO-08 package. We'll use an emulated SPI-mode since we're already using I²C for the RTC (with a DS1307) and the external memory (24LC256), but this works just as well. Resolution goes to one tenth of a degree Celsius!
H1 humidity sensor	This sensor's output is a capacitance between 112pF (at 10% RH) and 143pF (90% RH) Its curve is not linear so we'll use a simple table to convert the A/D reading to the correct RH-value. Capacitance to frequency conversion is done with a simple 555 timing circuit. This frequency is fed to the PIC's T1_CLK.
RX+TX433: wireless modules	These are cheap modules. They have a quite good range (to 25m indoors and 150m outdoors.) Data size of one packet is 32 bits. Bits 8 (LSB) to 19 (MSB) contain temperature data (BCD). Bit 21 is the minus sign, bit 23 is a low battery warning.

Schematics: right-click & "save picture as" for full resolution or (recommended) download the eagle-file below.

Base-station (receiver)

Transmitter

Remote temperature sensor (transmitter) compatible with HUGER & OREGON SCIENTIFIC remote sensors

Parts Lists (Bill of material):
Receiver, Calibration:
Pressure calibration
Make sure you're using a reliable multimeter, and not a cheap one. First adjust VREF- (PIC RA2, pin 4) to 2V40 with trimmer R9. Then adjust VREF+ (RA3, pin 5) to 4V70 with trimmer R8. At last, do a manual (linear) pressure correction via the menu (see below.) Of course, you'll have to know the current pressure for your area ... but this is just once!

Humidity calibration:
Make sure you're using a reliable multimeter, and not a cheap one. First adjust VREF- (PIC RA2, pin 4) to 2V40 with trimmer R9. Then adjust VREF+ (RA3, pin 5) to 4V70 with trimmer R8. At last, do a manual (linear) pressure correction via the menu (see below.) Of course, you'll have to know the current pressure for your area ... but this is just once!

Temperature calibration:
No need, the TC77 sensors are fully calibrated.

Downloads:
WARNING: may not be duplicated for any commercial use whatsoever without explicit consent from the author (c) Michel Bavin

For the base-station (receiver:)

Hex file: 012_v32_hex.zip, September 12, 2004: 012_32.hex (to program the PIC 18F452)

Source code: 012_v32_c.zip , September 12, 2004 : 012_32.c (CCS compiler) (with include files 24256_mb.c / ds1307_mb_v1.c / lph7779_v3.c / menu_012.c / rx_radio_012.c)

Schematic: 012_base_sch.zip , September 9, 2004: 012_base.sch (Eagle 4.11e) (with these library files: pic18f4x2.lbr and ic-package_mb.lbr (important: copy these to your eagle\library directory)

PCB: 012_base_brd.zip, September 9, 2004: 012_base.brd (Eagle 4.11e)

For the remote temperature sensor (transmitter:)

Hex file: 012_v105_hex.zip, May 6, 2006: 012_105.hex (to program the PIC 16F84A)

Source code: 012_v105_c.zip , May 6, 2006: 012_105.c (CCS compiler)

Schematic: 012_transmit_sch.zip , September 12, 2004: 012_trans.sch (Eagle 4.11e)

PCB: 012_transmit_brd.zip , September 14, 2004: 012_trans.brd (Eagle 4.11e)

PCB ScreenshotsBase station (receiver:)

Remote transmitter (outside temperature:)

Info and Data sheets

MPX4115A pressure sensor from Motorola.

TC77 SPI temperature sensor (Microchip.)

H1 humidity sensor (Philips.)

RX+TX433: wireless modules (Velleman)

DS1307 i²c RCT

24C256 i²c EPROM

Tools
This project is made with the PCWH CCS compiler ($500,-) You can install Microchip's free PLAB IDE with it to get things going smoothly.

Programming of the PIC18F452 was done with the excellent Tiny PIC bootloader, through the RC6 & RC7 pins. But you'll need a regular PIC programmer to write the PIC the first time with... The remote transmitter has software RS232 on pins 9 (RB3,TX) and 10 (RB4,RX) for debugging only. Eagle 4.11 was used for the schematic & PCB layout.

Comments

#1 | FATMAN2142 on May 09 2009 09:23:50

whats the LCD used?
full parts list?

#2 | BlackMASK on August 23 2009 11:37:59

Full parts list is available now. Please read above or click on this download link www.elxproject.co...?page_id=6.

#3 | kittupul on September 06 2009 11:10:06

can i have hex code and source code of this proj?

#4 | kittupul on September 06 2009 11:11:54

can we interface sd card to pic used in this project?how to interface that?
plz send circuit diagram of it?

#5 | kittupul on September 06 2009 11:13:04

reply fast

#6 | kittupul on September 06 2009 12:54:24

PLZ ATTACH BLOCK DIAGRAM.

#7 | BlackMASK on September 23 2009 11:29:20

You can download the hex code and source code. Please follow the download link to download

#8 | IronBrain on February 01 2010 12:01:10

Hello, This is an Amazing project. I see you have a wireless module. I maybe a confused undergraduate engineer here but I plan to follow your project as a guide so I can learn a few things is there a way I can interface the PIC to connect to a wireless network within range and the data get transmitted to a website for uploading current weather conditions? I am serious about learning what I would need to do to implement that and learn this project top to bottom thanks!