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Climate Logger

Recording temperature and humidity

Climate Logger
This electronic alternative to mechanical temperature and humidity recorders is a very compact standalone unit which draws very little current. The Dallas DS1616 device used comes already equipped with a temperature sensor, and besides a humidity sensor we can add a range of other sensing devices. The collected data can be transferred to a PC or notebook over an RS-232 port for analysis by user-friendly Windows software. The system can also be connected to a microcontroller board. The climate logger operates completely autonomously while it is carrying out a ‘mission’ (measurement sequence), and can run on battery power for a long period in this mode. The device can, for example, be left in the refrigerator or in the wine cupboard to continuously record the temperature and humidity. The Windows-based software running on a PC is used not only after a mission to download and analyse the stored data, but also before a mission to configure the data logger. With the aid of the software, both the sample rate and the selection of which channels are to be recorded can be configured.
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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.

Resistors:
R1,R7,R14,R15,R18 = 10kOhm
R2,R21 = 100kOhm
R3 = 47kOhm
R4 = 220Ohm
R5 = 68kOhm
R6,R11,R13 = 10MOhm
R8 = 470kOhm
R9,R12 = 1MOhm
R10 = 150 kOhm
R16,R17,R19,R20 = 1kOhm
P1 = 250kOhm preset (vertical mounting)
P2 = 2MOhm preset (vertical mounting)
Capacitors:
C1,C2,C3 = see text
C4,C5,C8,C10,C11 = 100nF
C6 = 22µ F 16V radial
C7 = 330nF
C9 = 10µ F 16V radial
Semiconductors:
D1 = LM385-2.5
D2= LED, red, 3mm, low-current
D3 = LED green, 3mm, low-current
D4,D5 = 1N4148
T1,T2 = BC547
IC1 = TS556
IC2 = 78L05
IC3 = MCP6041-I/P (Microchip) (Farnell # 396-8790)
IC4 = DS1616
Miscellaneous:
JP1 = pushbutton, 1 make contact
K1 = 3-way pinheader
Humidity sensor type HS1101 (www.humirel.com), available from Unitronic (www.unitronic.de)
K2-K6 = 4-way pinheader
BT1 = 3V Lithium cell
X1 = 32.768 kHz quartz crystal
BT2 = 2 UM-5 (AM-5) or AA batteries (depending on available enclosure)
9-way sub-D socket (female), angled pins, chassis mount
ABS enclosure with battery compartment (OKW size # 3 for AA cells, e.g. RS Components # 583-218)
PCB, order code 030076-1
Disk, Windows software, order code 030076-11 or Free Download
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