AquaCube (c) improvements notes

This is a note about how it would be possible to improve a pet fountains with some electronic.

Just bought an Aqua Cube for Freddy, our cat.
The AquaCube is a fountain with a filter capable to hold and keep clean and areate the water for the pet.
Very nice way to allow him to drink, but there are three problems to address.

Problems

1. remember to change the filter every 4 weeks 
2. remember to clean up the fountain every 5 to 6 weeks 
3. check the water level 

Change filter

The Aqua Cube has a charcoal filter and needs to be changed every 2 to 4 weeks (depending the number of pets using the fountain).It is hard to remember in such time lapse, when is time to change the filter.It is needed a reminder.

Cleaning

At least every 6 weeks the fountain should be placed off line and washed.
Also in this case it is needed a reminder.

Check water level

The pump must always run with water and of course, the pet must have water to drink.
It is necessary to have a system capable to stop the pump if there is not enough water and notify that water need to be added to the fountain.

The idea

Of course it is relatively easy to put together a contraption capable to perform such operations and eventually something extra.

Here some basic specifications for a circuit capable to cover these needs.

Specifications

• It must run with the power used for the pump 
• It must consume very low 
• It must have a battery backup in order to keep the count for the filter 
• It must be relatively stable (frequency) 
• It must be capable to drive a 12V rele' to power the pump 
• It must provide Visual/Acoustic notifications 
• It must have an input way to reset the conditions 
• Optional - sensing the presence of the cat to shut off the pump to avoid the noise 
• Optional - turning off the pump during some time (evaluate if there is an energy saving worth the job) 
• Optional - sending alert via email/SMS/RF/ something 

Building blocks

Processor

An easy way to build such contraption would be to use a MSP430 (Launchpad) with the 32Khz crystal.
This would be a great starting base for the project.

Battery backup

The contraption must have a battery backup kept charged when the main power for the pump is present (12V).

Water level detection

The next thing is to decide how to detect the water level.

Here some constraints :

• it must be NON toxic 
• there is no need for high precision 

Since the water is drank by pets, is better to avoid any contamination. So no metal bar in the water, better a touch-less way to measure the water level.

This paper contains some suggestions, but probably the easiest way is using a pressure sensor connected to a small plastic pipe, one used in aquarium, immersed in the water.

Notification

Maybe a LEDs capable to indicate the different status and/or acoustic signal to notify when there is not enough water.
Even better a SMS or email notification, indicating the reason of the alert.
It can contains details about the notification, like "water level too low", or "change filter" or "cleaning required".

Mechanical issues

Some constraints exists for the mechanical assembly.
The electronic should be placed in a sealed box, attached to the back of the fountain.
The box must be detachable from the fountain to allow it's cleaning.
From the box starts also a clean pipe for the water level. The pipe must be detachable as well.
In other words is better to avoid hardware modifications to the fountain in order to guarantee the prescribed maintenance as described on the user guide of the AquaCube unit.