• on Test & Measurement
  • Published in issue 1/2013 on page 78
About the article

Tropical or Arctic?

No Sweat! This Temp. & RH Meter logs it all

Tropical or Arctic?
This project, in order to be appealing in such an extensively explored subject, incorporates a number of interesting features never put together in one single circuit, some of which even only available on professional equipment. Its main functions are to measure temperature and relative humidity.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component List
R1,R14-R16 = 10k
R2-R5 = 3.3k
R6 = 560Ohm
R7 = 91Ohm
R8 = 374kOhm
R9 = 100kOhm
R10 = 1MOhm
R12 = 27Ohm
R13 = 4.3kOhm

C1,C9 = 1µF
C2 = 0.1µF
C3,C4 = 22pF ceramic
C5 = 2200µF / 16V
C6,C7 = 2.2µF
C8 = 22pF variable capacitor

D1 = LED, red, 5mm
D2-D6 = 1N4148
Q1-Q4 = BC237
Q6 = 2N2907
U1 = PIC18F4525
U6 = LP2953IN
U7 = MCP6042
U8 = PCF8583

BT1 = 9V rechargeable battery
BT2 = CR2032 with battery holder (Farnell #1020673)
J1,J2 = 3 pin SIL pinheader
K1,K2 = 3-pin screw terminal block, pitch 5 mm
K3,K4,K5 = 2-pin screw terminal block, pitch 5 mm
S1-S5 = tactile switch
SW1 = external (rocker) switch
TP1 = trimpot 10k
X1 = 8MHz quartz crystal
X2 = 32.768kHz quartz crystal
U2 = 4x20 character LCD
U3 = UM232R module (FTDI)
U4 = MCP9701 (Microchip)
U5 = HIH-4000 (Honeywell)
PCB 090925-1 [1]
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