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Liquid Level Controller: Low visibility in aquarium

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Sep 7, 2007
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aquarium level switch

I'm looking for ideas on how to build a fairly low cost yet reliable water level sensor in an aquarium. In principle the sensor would be used in a greater aquarium system that controls numerous aquarium functions in addition to automatically changing aquarium water.

The simplest idea I can arrive at is a 'short' sensor, in other words, if the water is at the level of the sensor the circuit could be completed with a very small current thus signifying a tank full state, rather than a tank not full state. In practice the controller would use the sensor state to determine to open or close a solenoid that would remain open till the tank was full.

The application in mind is freshwater (with appreciable TDS to conduct) although saltwater applications aren't out of the question. Traditionally inexpensive float sensors are utilized (**broken link removed**). The same manufacturer offers a conductivity switch (**broken link removed**) that is both relatively costly and requires a costly controller to operate.

Design considerations:

1. Low current as to not disturb tank inhabitants. They'd have to stick their head in it to get a surprise but I don't think it would take much to stun/kill a fish

2. Intermittent monitoring. As above to minimize disturbance.

3. Redundancy, failure in the sensor would result in water spilling onto a residential floor. Redundancy is necessary.

4. Provide a simple open or closed signal that could be utilized by a controller. Example: **broken link removed**. This model has the capacity to utilize a sensor to trigger a process.

5. Be as unobtrusive within the tank as possible, this is the disadvantage of the existing float sensors.

Can anybody suggest a starting point?

liquid level controller circuit

I've seen a capacitive sensor for water level. In this case you don't need the water to conduct current and add a substance.
The sensor is made of 2 single side PCBs, with the length coresponding to the level domain, painted for isolation and inserted verticaly in water. At the upper part you connect a wire.
The capacitance between the plates is very small with no water, and proportional to the water level. To determine the level, you need to measure the capacitance with a circuit/microcontroller.
hobby low cost liquid level sensor

I have an Idea!!
I've made a level meter device to measure fuel tank at a gas station. The device has a high precision and accuracy (sensitivity = 0.5mm). It uses one pressure sensor from freescale. I've made another prototype for my marine aquarium. It require 1mm level precision because when the level drop 1mm, it means that the salinity has change.

U can use a conductive sensor if only on/off status you need.

correct levels of visibility in salt water


I think we can use reed switches and a simple 555 circuit wired as bistable multivibrator to solve this.

Reed switches should be enclosed in plastic pipe and the pipe should be passed through a magnet.

No conduction in WATER, so no danger for fish

application of water level indicator wikipedia

I missed the post a while back, I'm going to have a look around for the part you've mentioned.

Re: Embedded Design

pls, can you help us with the circuit diagram of your solution and more elaboration on it. thank you

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pls, can you help us with the circuit diagram of your solution and more elaboration on it. thank you

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