Backyard Aquaponics
A place to discuss aquaponics

Sorry to confuse, I was looking at continuous flow system.

EKB allowing for power fail would be an interesting proposition- most of the pumps I’m looking at are at least 500W, most are closer to 1kW, a UPS/battery back-up for that would be pretty expensive if it was to run for any length of time, but is worth looking into. At the moment I’m only pricing power back-up for aeration rather than the whole system.
Some extra thought/logic/smarts would also be required to automatically switch back to the primary system when power returns. My first thought is not to switch the primary off at all (except for isolation) and on fail then logically (if not physically) run both pumps.

Got a little ahead of myself, using continuous flow pump and checking for pump flow:

backup could be a temporary system that covers both (power or pump failure) for a determined period to keep the fish alive - air pumps off dc working can run up to 10 hours, hopefully this would be sufficient time to replace a faulty pump or power to return.

Saves on expense of a pump sitting idle for extended periods - switching back could be a manual affair (reset button), doesn't really need to be complicated

Yeah thats fair enough, I just found a 500W-90l/min pump for $70, for that price I assume there could well be failures so I may as well buy 2 and spend another $50 on a swap over system. $190 for two pumps and no great fear of failure sounds like a win.

A 5400LPH pump which is 500W that seems unlikely? What type of pump is it. My 4500LPH dirty water pump only consumes 75W and I have measured it @ 78W. It is a far cry from 500W.

Anyway, I bought a kit from Jaycar that connects to a computer which has 8 digital inputs, 8 digital outputs, 2 analogue in and 2 analogue outputs. I plan on using an old laptop with a C++/VisualBasic program. The analogue inputs could easily run temperature probes, pH metres and conductivity (hardness/salinity). I am going to try and use linux as an operating system as I don't trust Windows operating systems.

I will have the ablility to run the whole system off solar where funny enough I will have mains power as backup.

Interesting point - if the power fails then the system has no power to detect if water flow has ceased, 2 options:
1) backup to the system
2) forget the whole idea of using it for power failure

I think option 2 just won

Wow 4500lph only using 75W, that’s pretty amazing, I haven’t been able to find anything with close to that kind of efficiency. What amount of head can it handle at that flow?
My requirement was for at least 3000lph @ 3.5m of head, capable of running 24/7. I also want to be able to t off to another line with about 500-1000lph @ 4.5m of head to run though solar black poly coils. I’ve been looking everywhere I can think of for something that can do this using ~< 500W at a reasonable cost. The one that came closest was model TCP130 from http://members.iinet.net.au/~weewaa/ng/ ... tml#centri (which is 375W, 0.5 hp, they change their rating units all over the page)

so what's the kits name pse Tim

"What amount of head can it handle at that flow?"
I think it is rated at 5 metres.

It is similar to this one.... 4500LPH 65W
http://cgi.ebay.com.au/Submersible-Foun ... dZViewItem

USB Experimenter's Interface Kit http://www.jaycar.com.au/productView.as ... BCATID=432

Remember EB saying that his system runs off the cost of two 75W light globes.

thanks Tim

TC,
What about the temperature probes/ hardness or PH. Got any links for that stuff.
I have borrowed a friends electronic PH tester - fantastic, so would love to do the others electronically for small cost.

Any thermocouple will give you an analogue signal. Cheapest ones would be the probes that are suited for multimetres. The software will convert it to temperature. pH probes may be harder to find so it may be a homebrew job. GH and salinity can be improvised using resistance and a gestimation of salinity, and I can imagine a hefty formula. I did used to have a site bookmarked that sold specific probes but they don't come too cheap.

Tim, alanloug inputs into data aquisition cards usually means voltage or current input.

Tc requires a fairly high impedence input plus cold junction compensation.

PLC's and smart relays usually have T/C adaptors, some plc's have built in support for T/Cs.

Other wise, even if you correlate Mv to temperature, you'll be out by the ambient temperature of the "cold juction"

PH probe inputs usually need to be in the 100 to 1000 Meg ohm impedence range (from memory)
Steve

All of this would have to be incorporated into the probe, I am not saying this is the best user-friendly way of setting up automation... it is for me. I am just getting som option sout on the table. It would not be hard for me to use digital inputs to read temperature either, it is ony 2 bits of data.

Not dissing you at all Tim , just sharing 6 years of process control knowledge.

The probes used in the multimeters are type K thermocouples, and the multimeter has a little thermistor in there that measures the cold junction and compensates.

The Mv to temp scale yes, you could program in via software, but if you hook at T/C straight up to a AI and it doesn't have CJC (cold juction compensation) then you'll be out by the ambient temp.

Get a thermocouple, put it on the table and let it sit for 10 mins

get a multimeter set on the lowest range of mv. (let that sit next to the T/C too. so everything is at the same temp)

Measure the output. it will be zero.

A T/C only produces a voltage proportionate to the DIFFERENCE between its hot junction (tip) and cod junction (plug)

So if you were measuring water at 27C and the ambient temp was 20C you would likely get an equivelat mV for 7 degrees.

Ell..what about using one of the digital outputs to tie up a solid state relay used in a fail safe cofiguration so that when the power drops out your solid state relay will pull in a dc pump to aerate the tank until the power returns and then the SSR automatically drops the dc pump out of the cct again?