07-07-2014, 01:54 PM
Presentation on Plants Watering Watcher
Presentation on Plants Watering Watcher.pptx (Size: 107.05 KB / Downloads: 14)
Introduction
Plants Watering Watcher is intended to signal when a plant is needing water.
A LED illuminates at maximum brightness when the ground in the flower-pot is too dry
It dims gradually as the water Level in the pot grows, turning off when the optimum moisture's level is reached.
HISTORY OF THIS MODEL
This little Project encountered a long lasting success in the field of electronics
Its first appearance on this website in 1999.
In the correspondence exchanged during all these years with many amateurs, some suggestions and also criticism prompted scientists to revise thoroughly the circuit making some improvements requiring the addition of four resistors, two capacitors and one transistor.
This resulted in a more stable and easy to setup device, featuring a more visible flashing indicator with no resort to ultra bright LED devices.
Extensive tests were also carried out with different flower-pots and probes.
Circuit Description
IC1D starts and continues to oscillate with a supply down to 1.24V or less.
IC1A is an inverter.
IC1B is a NAND gate IC. Its output is low only when both inputs are high.
With 47 ohms or less between the probes, an input is always low, so the output is always high.
With a resistance of only R8 between the probes, the voltage across C3 is high most of the time, so the gates output .
CIRCUIT OPERATION
When the soil is very dry, the LED flashes brightly, since the soil’s resistance is very high.
When the soil has been watered a few days before, but is drying, the LED flashes dimly,
When the soil is damp because it has been recently watered, the LED is off.
Note: The different soils have a different resistance. Also, sometimes, watered soil will continue to have a high resistance until the soil absorbs the water, a delay of about one hour.
Advantages
It can be used by Farmers for checking the moisture level of soil.
It can be used by Gardeners for supplying different quantity of water to different plants
Disadvantages
The main disadvantage of this model is that it does not give exact value of moisture level of soil.