Backyard Aquaponics
A place to discuss aquaponics

This is how my stop-gap home made pump controller works: (warning hobby electronics ahead)

* The state of the pump, on or off, is determined by one flip flop that holds the state and controls a relay at its output.
* All other components are only auxillary!

Now what the 555 doing?? The answer is that the 555 is really cheap and I use the flip flop inside it! I basically use the 555 timer IC as a flip flop due to its high current output (for relay) and low current input(water probes) because the pins 2 (trigger) and 6 (threshold) need almost no current input.

* The water probes are simply two wires and they make the threshold go high by closing the circuit from the threshold pin 6, and the supply voltage through a megaohm-range resistor.

The megaohm-range resistor makes sure little current flows through the water, through the water probes.

* There are two small keypad - switches connected so that the pump can be manually turned off/on if necessary.

* Note that this is also a timer! The 555 is already a timer IC so its easy. The same IC is used! A RC (resistor-capacitor) time delay thing is used with a variable resistance for delays. This RC delay network directly drives the trigger pin 2 and the capacitor is discharged through discharge pin 7

There is a small incomvenience - a big capacitor (I used a 4700 micro F to get delays upto an hour and 15 min).

I think one of the first things will be to find out what is IN the box before you look outside.......

A small PICAXE or similar would do a multitude of things. I haven't looked at DO sensor technology but it should not be difficult.

Ron

Though extremely simple and cheap, I want more features (greed? ) and my next one is going to be a microcontroller one.

This is because I want same features below.
(Also, microcontrollers are fairly cheap (really believe me! - here a meal or two at a restaurant costs as much as my favourite microcontroller (AVR)).

Here are some features I can add (and cheaply!):
* to monitor water levels and detect failures in siphons or blockages in water links before bad things can happen
* to monitor drain times and detect blockages in drain pipe before it can happen badly.
* to monitor water level drop due to evaporation and automatically prompt for water- refills (or maybe use a pump and do it on its own??).
* very good programmable timing - its cheap to even add a daylight sensor and change timing cycles so that less cycles can occur at night (to prevent temperature drop).
* it can log this and it can log that - very useful to pore at the graphs when bored
* temperature can be sensed really cheap (you can get down to a thermistor (NTC) and do some software caliberation and make it linear in software (the thermistor behaves exponentially I think) if you want to go really cheap)

* many more only limited by imagination

DO senors work (I think) by sensing the voltage of the probe dipped in the electrolyte (!! the AP water).
This is the cheap and easy part, the hard part is to make the voltage depend only on the dissolved oxygen, and this is done using a semipermeable membrane that only allows oxygen molecules to go through. That's the expensive part.


I may be wrong! This is a part guess.

No, my fish-at-top infrared sensor is really cheap. Cheaper than a meal at a restaurant here.
(Yes a real DO sensor is expensive)
I don't suggest that, the air pump switches on only if the fish-at-top low DO sensor detects enough fish for enough time.

Great ideas

Another cheap sensor to make on your own: A conductivity sensor.

Most microcontrollers (cheap) come with an in built ADC (like the AVR microcontroller). You need to make a conductivity meter with some caliberation.

Or you could use an old multimeter and hack it.
The probes or simply two plates of known area with a known distance of separation, dipped into the water to be tested.

Oops most of my ideas for my controller

These are slightly similar to the first post (jazzplayermark's). Didn't see that oops.

Other cheap control-freak ideas for a controller:
* Log light levels (cheap sensor) through the seasons near the growbeds at various angles (east,west, north, south). So you can see how the plants are getting sunlight.
(Yeah this is an outrageous control-freak idea but it's not expensive at all to DIYourself so why not hehe)
* Manage (electrical) power cuts and crises better automatically (like slowing the cycles down to a minimum during a power-cut to conserve backup battery power.)
* Manage multiple power sources (solar, wind, etc) if you have them and reduce use of grid power as much as possible. (If you have the solar/wind power things).

And in my next controller I am going to use a soft-start for pumps.

To any non-electronics person:
What it does is, it turns on the pump with low power, gradually increasing it to maximum. This minimises the shock that pumps get when switched on/off. Especially pumps meant for continuous duty.
This does away with any shortening of life due to switching on/off of pumps meant for continuous duty.(like my pump!)

gokul,

This post is just so you will not have to feel like you are talking to yourself ...

But actually, there are some great ideas you have there. I am involved in RE (Renewable Energy) and do realize the first four things one does on a system is conserve, conserve, conserve and conserve. As one of the main costs of aquaculture is moving water, it makes sense to me to keep the 'lifts' of the water as small as possible, therefore lowering power requirements.

The most efficient method I know of to move water is with a propeller in a pipe. With a variable speed motor one could pump just enough water to keep plants and fishes alive. BTW, these 'prop in a pipe' type pumps are low head and work better in larger systems.

On smaller systems I feel one may need to look at secondary pumps and even secondary air-pumps. This also my allow for some DC pumps as AC batteries are rare in my part of the universe and folks use inverters, another source of inefficiency. Battery voltage s can be monitored and even feeding times cut back or eliminated if ammonia becomes a problem.

All of these ideas become more viable the larger the system and therefore the larger budget and the greater potential for loss. This requires more in the budget for emergency backup.

Even if one isn't worshiping at the alter of global warming, they should understand conservation and paying less because they designed, or copied, an efficient, low power requirement system.

Ron

I agree about the pumping head in reducing energy loads by large amounts.

Water weighs a ton and every AP're knows it comes only next to gravel hehe.

You are lifting, say, half your tank water or so, by say two feet. Thats a big weight going up (to growbeds) and falling back.
(Imagine - lifting half the filled tank yourself and dropping it, every cycle through the day, week and year, to feel this point I made...)

If you do it with half a foot you use 1/4 of the energy. Water lifting and dropping every cycle is the most energy consuming part of an AP system. By reducing here you will reduce a large part of the overall energy demand.

( I personally am embarrased to say I have a large head than necessary but it is a 15W pump, a really small system. Large systems will benefit from hairy optimization.)
"Hairy optimization" - a term from the computer world where you optimize your program so much that it may run much faster but the program looks hairy (scary)).

DC pumps are very inneficient ,, better re-think that one.

I'm not sure how the whole disolved oxygen thing works technically but I do know that my Tilapia will come to the surface in a nano second if the DO is low. The ONLY time this has ever happened is when I've done a big water change and pump a lot of well water into the FT. Well water, I understand is very low on DO and the fish detect that immeadiately. I get a fair amount of aeration when my GB sump pump sends the water back to the fish tanks and I believe that's all I need.

So basically, if my pumps are working ( I check for that now with some level sensors) I know my system DO is ok. That is using the assumption that if the fish aren't at the suface there's not a problem.

Any other thoughts?

DO ,, is not just about fish survival , it is about efficient growth rate.
Your DO may well be at 2ppm and Tilapia can live ,, but they would be growing SLOWLY.

Keeping optimal levels of DO , Temp PH etc ( within reason) leads to efficient usage of the system in doing it's task , i.e producing food.
Never assume your DO is at optimal level just because your fish are not dying or suface sucking.