Agriculture Reference
In-Depth Information
An Assortment of Wall Chargers
Source:
HowToGeek.com
While this source of power can come from many different places, the easiest and most
readilyavailablesourceformostpeopleisabatterychargerthatyoumayhavelayingabout
from an old cellphone orother consumer electronics device. These types ofpower supplies
have a typical power rating of 3 to 5 volts (VDC) at approximately 250 milliamps (mA)
being equal to about 1.25 watts of power. If the power supply you have operates under
different specifications, that's okay too. In practice, far-less than the rated current will be
used in your plants.
Note: Some power supplies label the cord in such a way that the positive lead is marked, e.g. with a white
stripe. At this time the polarity of the power supply does not matter.
Battery-based Power Supplies
Batteries can be a great way of setting up a remotely-powered system for very little cost.
Even if the batteries need to be replaced from time to time, while it is a big inconvenience,
for those who are in cost-sensitive situations, it can be a good option for getting started.
Yet batteries have a number of drawbacks, as to be described in the following paragraphs.
Thefirstproblemisthatbatteriesneedtobesizedcorrectly.Ifthebatterygets“loaded”too
much, or it's presented with too much of a current draw, then its lifetime can be severely
affected. For example, when the soil is medium-dry, it could be considered to be a normal
condition. Yet when the soil is wet, or soaking-wet, the current flow will be much higher
because when more water is present, the soil resistance will be much lower than normal,
allowing for greater amounts of current to flow. In addition to altering the battery's life, it
