For $6 on ebay you can get a battery powered sensor/alarm that beeps if the water level in a toilet tank gets too high, indicating a clog or stuck valve or something. Great; not what I need. Last night a toilet ran all night because of a tangled chain, so I need a too-low system, not a too-high system.
My thought is about a sensor/timer/beeper that tests if the water level in the tank is too *low* for too long a time. This would indicate if the flush valve were stuck open (tangled chain, etc.) because the water level stayed below x inches for over 1 minute, or something like that. Small plastic case stuck on the back or side of the tank, two wires up under the lid and wire-tied to the fill stem at an appropriate sensing height. The question is about optimizing the design so a standard 9 V battery lasts years. Hopefully it actually beeps very rarely; I'm looking at the static current through the sensor conditioning. Something very low power detects no water between the sensor tips and releases the reset input of a CD4060. I've got everything after that.
This project is in the schematic puttering stage. My first thought is a 2N7000 MOSFET with 10 M ohms from the gate to the 9 V, and the sensor tips between the gate and GND. The FET is in series with the rest of the circuit GND net and the battery negative terminal. Yeah, it is DC, and I've seen enough water sensing threads to know what y'all think of that. But what about a couple of heavy gold plated connector pins for the tips?
ak
My thought is about a sensor/timer/beeper that tests if the water level in the tank is too *low* for too long a time. This would indicate if the flush valve were stuck open (tangled chain, etc.) because the water level stayed below x inches for over 1 minute, or something like that. Small plastic case stuck on the back or side of the tank, two wires up under the lid and wire-tied to the fill stem at an appropriate sensing height. The question is about optimizing the design so a standard 9 V battery lasts years. Hopefully it actually beeps very rarely; I'm looking at the static current through the sensor conditioning. Something very low power detects no water between the sensor tips and releases the reset input of a CD4060. I've got everything after that.
This project is in the schematic puttering stage. My first thought is a 2N7000 MOSFET with 10 M ohms from the gate to the 9 V, and the sensor tips between the gate and GND. The FET is in series with the rest of the circuit GND net and the battery negative terminal. Yeah, it is DC, and I've seen enough water sensing threads to know what y'all think of that. But what about a couple of heavy gold plated connector pins for the tips?
ak