A circuit that offers visual indication of fluid level in a vessel, with a switchable audible alarm. Example uses would be to monitor the level of water in a bath or cold storage tank.
This circuit will trigger with any fluid with a resistance under 900K between the maximum separation distance of the probes. Let me explain further. The circuit uses a 4050B CMOS hex buffer working on a 5 volt supply. All gates are biased off by the 10M resistors connected between ground and buffer input. The “common” probe the topmost probe above probe 1 in the diagram above is connected to the positive 5 volt supply. If probe 1 is spaced 1 cm away from the common probe and tap water at 25 ° C is detected between the probes (a resistance of 20k) then the top gate is activated and the LED 1 will light. Similarly if probe 2 at 2 cm distance from the common probe detects water, LED 2 will light and so on. Switch 1 is used to select which output from the hex buffer will trigger the audible oscillator made from the gates of a CMOS 4011B IC.
Source: Circuit : Andy Collinson
http://www.mitedu.freeserve.co.uk/Circuits/Alarm/water_lev_alm.htm
Related Links
Water level alarm
Water sensor alarm
4011 integrated circuit
Water Alarm with LM380
Water Activated Alarm by IC 555
Water Sensor Alarm Kit
Water Alarm Circuit Diagram
This entry was posted on Sunday, April 13th, 2008 at 10:20 am and is filed under Audio - Alarm, Digital, Electronic Control.
