Backyard Aquaponics
A place to discuss aquaponics

I reckon the build up of crap will reduce the conductivity between the probes...spoken as one of those with the electrical knowhow

The 2 sensors need to have a full bridge of water between them for it to set off the alarm.

A splash would not (unless a very big splash do that.

The further apart the sensors the less splashes could upset it.

Also - if the real wizzkids also incorporated a delay timer so that both probes need to be covered for x seconds before the pump switches on then that would help even more. Although from testing the unit I have I really dont think it would be necessary.

The main thing is that the probes will normally be under water most of the time...when the sump level lowers and the probes are uncovered, then it needs to give an alarm (switch a relay) to put more water into the sump and cover the probes.

Eventually a biofilm will cover the probes and the readings will be out...the same thing will happen with a ball type float valve.

Ultrasonic methods are starting to be more viable because the transducers will be out of the water all of the time, they will measure the distance to the water and switch the relay when the distance is greater than required and start filling the sump tank back up....well that's the theory

I reckon this was covered in the old forum somewhere, ultrasonic probes( as mentioned by Les) would be the way to go...or the float switch because neither would become less reliable as a conductive type probe due to the coating of the probes in an AP application.........

a latching relay would possibly be easier to incorporate than a timer

bk, I think he's wanting to debounce the switch, not latch it on the first false positive. A 555 timer would do well to debounce.

yep I know what he wants to do lol.....

Here is a nice little range finder for you Kuda

http://www.robotparts.com.au/srf02.htm

These guys have some really interesting stuff. In particular this one that seems to use 2 float switches and a little evelectonic brain so there is a backup if one float switch doesnt work for some reason. Built in redundancy.

http://www.virtualvillage.au.com/Items/ ... Controller

There other stuff is also quite good - things like temperature controllers and things - look here.

http://www.virtualvillage.au.com/Aquarium-Accessories/

This item in particular might be good to use as a diferential thermometer for the solar heating croud. http://www.virtualvillage.au.com/Items/ ... with%20ATC

They take out all the fun of building one, DIY style Hamish :chuckle:

Good links tho, thanks for that...there is a DS18B20 (1-wire digital thermometer) that can be connected to a micro-controller...if anyone is interested (<$10 each)

...must see about rigging up some

No fun building thisone but looks great ,,assume it'sjusta pressure differential swith with relay.
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... ink:top:au