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Soil Moisture Tester

for houseplants

Soil Moisture Tester
For those of us who don’t like to get their hands dirty, this simple tester quickly checks the state of their plants and how much attention they need. Recommended for all plant owners!Plants seem to have something in common with pets. They are usually acquired or given with the best intentions, but not everybody seems to be able to look after them properly. Of course we do not expect everybody to have green fingers, but when plants are not watered enough they simply die. In any case, too much neglect usually has fatal consequences. Cactuses seem to survive such a careless treatment the longest and we have to admit that these are the only plants that manage to survive at our offices.So what can we do about it? It’s simple really. All it needs is for regular checks to feel if the soil in the pot has become too dry. But what is ‘too dry’? Some people just don’t seem to have the right fingers for this task. A little electronics can be used to rid us of this problem forever.
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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 = 100kOhm
R2 = 2kOhm 7
R3 = 2kOhm 2
P1 = 500kOhm preset H
Capacitors:
C1 = 470µF 16V radial
C2,C3 = 10µF 16V radial
C4 = 100nF
Semiconductors:
D1 = 1N4001
D2 = 1N4148
D3,D4,D5 =LED, green
D6-D9 = LED, yellow
D10,D11,D12 = LED, red
IC1 = LM7805
IC2 = LM3914-N
Miscellaneous:
Tr1 = mains transformer, secondary 6 V 200mA ( e.g., Monacor/Monarch VTR-1106)
F1 =fuse, 200 mA, with PCB mount holder
JP1 = short-circuiting jumper
K1 = 2-way PCB terminal block, lead pitch 7.5mm
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