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Following Device (circuit) to indicate the water level of two different tanks.

N MOSFET is used as sensor and 5 LEDs as output to indicate water levels.

Switches S1,S2,S3,S4,S5 are coming form tank one; and S6,S7,S8,S9,S10 are coming form tank two.

Separator S11 is used to switch between tank 1 and tank 2.

enter image description here

I think Separator is not enough to switch between two tanks which produces Mix/Misleading results.

I can not figure out, how to isolate both tank's output using Separator and diodes. I can understand there must be diodes to block current flow kindly help..

Update: added 2 diodes between S1 and R1, and also between S6 and R1. still did not get what it suppose to do.

enter image description here

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  • \$\begingroup\$ Did you think that D6 wouldn't conduct? \$\endgroup\$ Oct 29, 2017 at 15:49
  • \$\begingroup\$ @IgnacioVazquez-Abrams D6 suppose to block the current flow. Fact is I don't understand where to place this diode? \$\endgroup\$
    – VBAbyMBA
    Oct 29, 2017 at 16:10

1 Answer 1

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You should delete D6, and add diodes (pointing down) between EACH switch and its associated FET gate and pull-down resistor.

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  • \$\begingroup\$ Did you mean first diode should be in between S1 and R1? \$\endgroup\$
    – VBAbyMBA
    Oct 29, 2017 at 16:17
  • \$\begingroup\$ Yes, you need a diode between S1 and R1, and also between S6 and R1 - repeat for each LED. \$\endgroup\$ Oct 29, 2017 at 16:25
  • \$\begingroup\$ Where do you get "5 diodes in series"? You want one diode in series with each switch. \$\endgroup\$ Oct 29, 2017 at 16:39
  • \$\begingroup\$ updated circuit is added to question kindly take a look. \$\endgroup\$
    – VBAbyMBA
    Oct 29, 2017 at 16:57
  • \$\begingroup\$ You should remove the wire at the top right, where D6 was in your original drawing - that wire shorts S11. You need to add pairs of diodes like D6 and D7 in each "channel". \$\endgroup\$ Oct 29, 2017 at 17:41

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