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Barometric Altimeter

Mountaineers, delta glider and UL pilots -- this one's 4 U

Barometric Altimeter
In this project a piezoresistive transducer measures the atmospheric pressure, enabling a PIC microcontroller to use the ISA model (with temperature compensation) to display your current height above sea level (ASL) on an LCD.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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Extra info, Update

Specification and features
Altitude range: 0 to 11,000m A(M)SL
Compliant with ISA model, extended with temperature compensation
Barometer range: 15 kPa to 115 kPa
Resolution: 3 m.
Temperature range: –55 °C to +125 °C
Real Time Clock
Supply voltage: 6–15 VDC;
Current consumption
- LCD backlight on: 18 mA;
- LCD backlight off: 8 mA;
- Standby: 20 µA
Menu controlled
Software: C for PIC

Download the BOM list
The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
Want to learn more about our BOM list? Read the BOM list article for extra information.
(1%, SMD 0805)
R1, R6 = 1kohm
R2 = 100kohm
R3 = not fitted (see text)
R4 = 0ohm
R5 = 10kohm
R7 = 4.7kohm
R8 = 750ohm
R9 = 100ohm

C1,C10 = 47µF /35V radial electrolytic, lead pitch 2.54mm (0.1")
C2,C3,C5,C6,C12 = 100nF 50V ceramic, X7R, SMD 0805
C4,C13 = 10µF 16V radial electrolytic, lead pitch 2.54mm (0.1")
C7 = not fitted (see text)
C8,C9 = 15pF ceramic, NP0, SMD 0805
C11 = 10nF 50V ceramic, X7R, SMD 0805
C14 = 330nF ceramic, X7R, SMD 0805

D1–D5 = TS4148, SMD 0805 (Farnell # 8150206)
IC1 = MCP1703T-5002E/CB, SOT-23, (Farnell # 1439519)
IC2 = TC77-5.0, SOT-23 (Farnell # 1292291)
IC3 = PIC18F2423, SO-Wide, programmed, Elektor Shop # 080444-41
IC4 = MPXHZ6115A6U or MPX5100A (Freescale), SSOP (see text)
T1,T2 = FDV304P, SOT-23 (Farnell # 9846123)

K1 = 4-way SIL pinheader, right angled solder pins, lead pitch 2.54mm (0.1")
K2 = 5-way SIL pinheader, right angled solder pins, lead pitch 2.54mm (0.1")
L1 = 10µH ferrite inductor, SMD 1812 (Farnell # 1174073)
LCD1 = 2x16, alphanumeric, DEM16217 SYH-PY /V, e.g. Elektor Shop # 030451-72
PC1,PC2 = solder pin, 1mm diam.
S1–S4 = switch, tactile, SPNO
X1 = 32.768kHz quartz crystal, cylindrical case
4 PCB supports, nylon, 12mm height, 4.6mm diam. (Farnell # 1325986)
PCB, ref. 080444-1 from www.thepcbshop.com

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