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ДЕТЕКТОР НА ВОДА |
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ТЕХНИЧЕСКО ОПИСАНИЕ |
| Показана е схема на прост индикатор за наличието на вода . Най-вече може да се използва за сигнализация при достигане до определено ниво на водата в различни конструкции . Датчика на устройството (съпротивлението на водата , показано като R3 на схемата) представлява обикновен електрически проводник . За повишаване на надеждната работа на устройството за електрод е необходимо да се използва метал, устойчив на корозия , например посребрена пластина или от специална стомана . Особено внимание да се обърне на устойчивото свързване на датчика със съединителния кабел на устройството , особено при големи разстояния (няколко десетки метри ) . В този случай трябва да се използват проводници с по-голямо сечение и е необходимо надеждно да се заземят устройството и водната конструкция . При наличие на недопустими смущения по свързващия проводник може да се конструира датчика с два симетрични електрода и да не се използва заземяването на конструкцията . |
Очень простая схема, а пригодиться может: да везде. Можно
положить датчик в кошачий сортир, и вы всегда будете знать о состоянии
мочевого пузыря зверя. Правда есть опасность испугать животину, так что
будьте осторожны.
Схема индикатора:
Всего делов то, что одна микросхема. Когда намокает датчик SE1, начинает пищать зуммер и загорается светодиод. Чтобы выключить тревогу надо высушить датчик и нажать кнопку S1.
В схеме используется зуммер со встроенным
генератором. Конструкция датчика может быть любой, например можно
вытравить вот такой рисунок на куске фольгированного стеклотекстолита.
У микросхемы есть забугорный аналог - это CD4093.
Источник: www.radiokot.ru
Parts List
R1 = 10 ohm, 10 watt, wirewound R2 = 100 ohm, potentiometer, wirewound R3 = 1 Mega-ohm potentiometer T1 = Transformer, 12.6volt, 1.2amp (min) SCR1 = Silicon Controlled Rectifier, C106Y1, NTE5452, or equivalent TR1 = TRIAC, SC141D, NTE5608, etc., rated 6-10 amp, 200-400 volt. TO-220.
Fuse = Slow-blow, 2 amp.
| Water Activated Alarm |
 Circuit Notes The circuit uses a 555 timer wired as an
astable oscillator and powered by the emitter current of the BC109C. Under dry
conditions, the transistor will have no bias current and be fully off. As the
probes get wet, a small current flows between base and emitter and the
transistor switches on. A larger current flows in the collector circuit enabling
the 555 osillator to sound. An On/Off switch is provided and remember to use a non-reactive metal for the probe contacts. Gold or silver plated contacts from an old relay may be used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard. These will eventually oxidize over but as very little current is flowing in the base circuit, the higher impedance caused by oxidization is not important. No base resistor is necessary as the transistor is in emitter follower, current limit being the impedance at the emitter (the oscillator circuit).
Description 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. The Conductance of Fluids Conductance is the reciprocal of
resistance. The conductance of fluids vary with temperature, volume and
separation distance ofthe measurement probes. Tap water has a conductance of
about 50 uS / cm measured at 25°C. This is 20k/cm at 25°C. Circuit Notes 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 onnected 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.Placement of Probes As 7 wires are needed for the probe I
reccommend the use of 8 way computer ribbon cable. The first two wires may be
doubled and act as the common probe wire. Each subsequent wire may be cut to
required length, if required a couple of millimetres of insulation may be
stripped back, though the open "cut off" wire end should be sufficient to act as
the probe. The fluid and distance between probe 6 and the common probe wire must
be less than 900k. This is because any voltage below 0.5 Volt is detected by the
CMOS IC as logic 0. A quick potential check using a 900k resistance and the
divider formed with the 10M resistor at the input proves this point: 5 x (0.9 / (0.9+10) = 0.41 Volt As this voltage is below 0.5 volt it is interpreted as a logic 0 and the LED will light. If measuring tap water at 25 C then the distance between top probe and common may be up to 45 cm apart. For other temperatures and fluids, it is advisable to use an ohmmeter first. When placing the probes the common probe must be the lowest placed probe, as the water level rises, it will first pass probe 1, then 2 and finally probe 6.
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