I had built the circuit from about a year... I designed it to give the number of barrels in a 10-barrels water reservoir. There is a positive voltage line at the bottom of the reservoir, and for each level there is a line (wire)-their terminals, the sensing points, are fixed on a long plastic rod and distributed with equal distances along the rod according to the volume, when water reaches the line, then its number is shown by a 7-segment display... A priority encoder is used. This project works fine but the copper wires (the level sensors) react and oxidize with time... I clean them periodically.
The sensing lines are connected each to the base of npn transistor so that if water reaches the sensing point then Ib flows and Vc becomes 0 logic, and it is 1 when there is no water..
As I noticed, the high humidity between the sensing points on the plastic rod in the reservoir is allowing low current Ib to flow and therefore everything becomes wrong, the 7-segment display shows no clear numbers but all its leds lightens but with different intensity.
The attached circuit could help you understand what I mean specifically, and shows what can I edit in the circuit to solve the problem.
I thought about replacing the collector resistors with 1K ones and placing resistors between the base and the ground.
note that this device is not powered always but only when I press a switch to see the level...
The sensing lines are connected each to the base of npn transistor so that if water reaches the sensing point then Ib flows and Vc becomes 0 logic, and it is 1 when there is no water..
As I noticed, the high humidity between the sensing points on the plastic rod in the reservoir is allowing low current Ib to flow and therefore everything becomes wrong, the 7-segment display shows no clear numbers but all its leds lightens but with different intensity.
The attached circuit could help you understand what I mean specifically, and shows what can I edit in the circuit to solve the problem.
I thought about replacing the collector resistors with 1K ones and placing resistors between the base and the ground.
note that this device is not powered always but only when I press a switch to see the level...
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