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Circuit for RV water tank level indication. There are five wires going to the tank, which are placed inside the tank vertically each at different height. When the water level rises, it connects the lowest wire with other wires, depending on the level.
Water level is shown by means of four LEDs, which represent 25, 50, 75 and 100%. Since there are two water tanks inside a RV (fresh and waste), the pushbuttons select the tank and power up the circuit, indicated by a blue LED. The switches represent water connecting wires inside the tank. After the conncetion is made, it feeds current to an NPN transistor base, which allows collector- emitter current to flow and turn on the appropriate LED.
(Indikacija nivoja rezervoarjev v avtodomu. S stikalom izberemo rezervoar za svežo ali za odpadno vodo. NPN tranzistorji delujejo kot stikala za LED diode, ko skozi BE steče tok, CE prevaja. Uporabljeni 11k ohm upori omejijo B-E tok, 360 ohm upori pa omejijo tok skozi LED diode. Dve diodi sta uporabljeni za ločitev napajanja LED diod glede na izbrani rezervoar. Modra LED dioda sveti pri vklopljnenem vezju (stikalo gor ali dol).)
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