(Continued from Part 1. This concludes the article.)
Back to First Principles
What would be really useful would be a series of lights which would reflect how full the tank was, and if in addition to that, an audible alarm for high water-level. Perhaps I could build something like this using basic off-the-shelf electronic components and my rather rudimentary knowledge?
Like most reading this, I am no engineer, and no electrician. My only personal asset seems to be that, I like to tinker with stuff. So, I dug out the multimeter and an old breadboard and began to experiment. To save time for others who are trying to solve a similar problem, a description of what I finally concocted follows.
I ended up using five NPN transistors (BC547), as shown in the schematic diagram below as having the arrow pointing away from the base towards the emitter.
Transistors have three pins: collector, base, and emitter. A transistor acts as a solid state switch turning on with a positive voltage applied to the base. To figure out which pins are which, refer to the spec sheet that came with the transistors. The BC547’s I used came in what is known as a TO-92 package which, with the flat face up, leads towards you, left to right: collector (1), base (2), and emitter (3).
By creating my probe using a fiberglass rod, I placed six bands of copper, at the bottom and at 9 inch intervals. The bottom band was wired to the plus (+) power supply. At heights of 9, 18, 27, 36 and 45 inches each was wired to the base of an NPN transistor through a 330 ohm resistor.Continue reading“How Much Water? – Part 2, by R.E.”
