Water Activated Monostable Switch

[tom08]

hi all
For my GCSE Electronics project i am planning on making a duck that, when placed on water, flashes a series of lights and quacks for a set period of time. My plan is to use monostable>astable>decade counter. Ive seen a few monostable 555 touch circuits but i dont know how to get it to be activated by water. what do you suggest? thanks

 

[crutschow]

Use a CMOS gate with a high resistance to ground (say 10MΩ). Then connect the gate to one electrode that contacts the water. Connect another electrode that contacts the water to the plus supply. When the contacts are in the water they should conduct enough current to raise the voltage on the gate to a logical one and turn the gate on.

 

[transistor495]

Good project

..or you may use this kind of activation connected to a delay timer + led flasher + how you're making the quack sound?

 

[tom08]

The quacking sound will be produced via a voice module. thanks for the ideas ill check both out.

 

[transistor495]

Well, this monostable section can be followed by the water activated switch described above(but with minor modifications regarding the power supply condition), T1 will be swiched ON for a particular time period as set by the pot, so by attaching the light flasher circuit with quacker you get the electronic duck in operation.

PS: You may try alternative methods

 

[tom08]

how about i just do a normal 555 monostable timing circuit with a liquid sensor where the switch is. here's a liquid sensor link : **broken link removed**

 

[KMoffett]

Just bench tested this. Water sensor and monostable in one. No need for a special sensor...just two wires.

Ken

 

[transistor495]

Hello tom08,
The solution suggested by Ken is an alternative way of doing it