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  • KlausM5 commented on sathishk12's instructable WATER LEVEL INDICATOR USING ARDUINO7 months ago
    WATER LEVEL INDICATOR USING ARDUINO

    Hi, I think the values for the resistors R1, R2 and R3 are specified too low. They should be at least 220Kohm. I used 470Kohm since the water 'resistance' is about 1-2Mohm. Also omit unspecified resistor in the 5V line that goes into water. caomitted.omit the

    Hi, I think the values for the resistors R1, R2 and R3 are specified too low. They should be at least 220Kohm. I used 470Kohm since the water 'resistance' is about 1-2Mohm. Also omit unspecified resistor in the 5V line that goes into water. Resistors R4, R5 and R6 will adjust the collector current, so choose higher than 470ohm if you want less than 10mA, like 1Kokm ->5mA. Logic levels with this circuit are 'high' for no water contact and 'low' for water contact. I used a 2SC945 standard bipolar NPN transistor and it works reliably. Good luck.

    additional comment. You can add a 1 kilo-ohm resistor in series with the 5V 'common' wire to protect the transistor against damage from accidently touching the wire ends directly.

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