PID controller setup ... for fish?!

[DaveMcPhee]

Ladies and Gentlemen,

Long time homebrewer here, who recently got into the the fun hobby of aquaponics, a system that has a lot of similarities to electric brewing, I swear. Aquaponics is a system that combines fish farming with hydroponics, the growing of plants in a soil-less environment using pumped water full of nutrients. In my case, the dirty fish water (full of poop) is pumped into a growbed full of river pebbles, where plants grow, cleaning and filtering the water for the fish. It's excellent fun, strongly recommended if you enjoy the kind of tinkering involved with electro brewing.

Here's why I'm posting here. The aquaponics community is mainly gardeners and off-the-grid type folks, with very little technical experience and guides, unlike this forum.

I need to build a very simple setup of a roughly ~1200W water heater, hooked up to a PID and a relay. Is there a simple beginners guide to setting something like up around here? A quick review and search shows lots of complex systems, but I'm just looking for the basics. Any help much appreciated

I'm looking for wiring guides and considerations, how to select a PID and thermocouple, setup considerations, gotchas, etc. I don't know enough to know what I don't know

And having browsed this forum for years, I know I can trust opinions posted here.

Thank you!

 

[binabik]

What kind of fish are you raising? I've thought about it, but don't have the space here.
Maybe my next place.

I don't have schematics or anything right now (at work), but the ST-1000
would work. It's very simple It has a switched Hot wire that's routed to the
HEAT side and to the COLD side. Since you likely won't need to cool down the
water you'll only need to worry about the hot side.

Do you want to heat the water going into the plant side or the fish side (or both)?
You can look at using an aquarium heater. You likely don't need to raise the temp
more than a few degrees.

If you can provide a basic layout of your system we can provide a better recommendation.
Also how many gph do you need to heat and how fast? Is it a continuous flow setup or
an cycled setup?

All those would factor in to where to place the temp sensor and the best place to heat the
water. IMO.

 

[DaveMcPhee]

What kind of fish are you raising? I've thought about it, but don't have the space here.
Maybe my next place.

I don't have schematics or anything right now (at work), but the ST-1000
would work. It's very simple It has a switched Hot wire that's routed to the
HEAT side and to the COLD side. Since you likely won't need to cool down the
water you'll only need to worry about the hot side.

Do you want to heat the water going into the plant side or the fish side (or both)?
You can look at using an aquarium heater. You likely don't need to raise the temp
more than a few degrees.

If you can provide a basic layout of your system we can provide a better recommendation.
Also how many gph do you need to heat and how fast? Is it a continuous flow setup or
an cycled setup?

All those would factor in to where to place the temp sensor and the best place to heat the
water. IMO.

Great questions, thank you. It's tilapia, who really don't like going below 55F - I'm going to shoot for 70f throughout the texas winter.

The whole system contains about 350 gallons of water that is cycled through the whole system every hour. Due to the size of the system and the fact that it's outside, regular aquarium heaters won't cut it, hence the big element. I also prefer to have more control and be able to adjust the element size if needed.

I have a sump tank, with a pump that pumps into the fish tank, and then it flows to various other parts, including the grow beds which are the primary cause of temperature fluctuations (they are essentially giant heat sinks).

I was thinking about placing the heating element in the sump tank, and the thermocouple in the fish tank. Can a PID handle such a large ... variance / system?

 

[binabik]

My experience with the ST-1000 is for a fermentation chamber. It just turns on the refrigerator to bring the temps down to the proper fermentation temperature for my beer.

The issue I see with that setup is you are monitoring the temperature in fish tank but adjusting the temperature in the sump tank. My concern would be heating the water too much causing a fish kill, since as long as the temperature sensor is below the cutoff temp of 70 F the heating element would still be on heating the input water. Granted you need to bring the 350 gallons up to your temperature (70f). It would seem to me that you would want to heat the water going into/coming out of your recirculation pump. IMO. They make commercial grade aquarium heaters, but if you want to save a few dollars and build your own you can do it similar a RIMs tube or a HERMs. There is a lot of info on this board for those setups.

That's my two cents. Good luck and keep us informed.

 

[DaveMcPhee]

My experience with the ST-1000 is for a fermentation chamber. It just turns on the refrigerator to bring the temps down to the proper fermentation temperature for my beer.

The issue I see with that setup is you are monitoring the temperature in fish tank but adjusting the temperature in the sump tank. My concern would be heating the water too much causing a fish kill, since as long as the temperature sensor is below the cutoff temp of 70 F the heating element would still be on heating the input water. Granted you need to bring the 350 gallons up to your temperature (70f). It would seem to me that you would want to heat the water going into/coming out of your recirculation pump. IMO. They make commercial grade aquarium heaters, but if you want to save a few dollars and build your own you can do it similar a RIMs tube or a HERMs. There is a lot of info on this board for those setups.

That's my two cents. Good luck and keep us informed.

Yeah the "timing" of a PID controller is a concern, I have no idea how fast ~300 gallons of water are heated with a ~1200W element, and will it know to shut off in time? Does a PID have the intelligence to ramp up slowly and observe results in temp change, or does it go full blast, overshoot, then correct?

 

[binabik]

They way my controllers work for my electric brewery setup is that either the heating element is on or off. According to the program when it is within 5 degrees of my target temp it cycles that element on/off until I reach my temp goal. Then it is off until the temp drops. That's why I would not have the water heat up in one place and measure the temp in another.

You can easily figure out how much power is needed. Start with a BTU which is the amount of energy needed to heat 1 lb of water by 1 degree. A gallon of water weighs about 8.3 lbs (IIRC). So that's 8.3 BTUs per gallon per degree F. To heat 350 gallons by 1 degree F that would be 2905 BTUs. 2905 BTU = 0.851165 kW With a 1500 W element you'd be able to heat the 350 gallons by 1.76 degrees. Of course that all depends on flow rate over the element. The faster the flow rate the less it will heat due to the shorter contact time.

It all depends on how quickly your pump recirculates. Since the element will be on when your temp falls below where you want it that element will stay on. The STC-1000 is either on or off. For finer control you'll need a different PID.

 

[DaveMcPhee]

They way my controllers work for my electric brewery setup is that either the heating element is on or off. According to the program when it is within 5 degrees of my target temp it cycles that element on/off until I reach my temp goal. Then it is off until the temp drops. That's why I would not have the water heat up in one place and measure the temp in another.

You can easily figure out how much power is needed. Start with a BTU which is the amount of energy needed to heat 1 lb of water by 1 degree. A gallon of water weighs about 8.3 lbs (IIRC). So that's 8.3 BTUs per gallon per degree F. To heat 350 gallons by 1 degree F that would be 2905 BTUs. 2905 BTU = 0.851165 kW With a 1500 W element you'd be able to heat the 350 gallons by 1.76 degrees. Of course that all depends on flow rate over the element. The faster the flow rate the less it will heat due to the shorter contact time.

It all depends on how quickly your pump recirculates. Since the element will be on when your temp falls below where you want it that element will stay on. The STC-1000 is either on or off. For finer control you'll need a different PID.

Thank you! I actually ended up getting this thing: http://www.amazon.com/gp/product/B007H5GQUY/?tag=skimlinks_replacement-20

Does that operate the same way, or does it have more "intelligence"?

 

[Bellybuster]

Measure your water temp at the fish tank and heat it just prior to that. the PID controller should be more than capable of giving you stable tank temp. The input water may be a couple degrees higher but the tank will be stable.
Read up on auto tune. It works well
If you heat the water before the plants and measure it after you run the risk of supplying your plants with too hot water.

Insulation is a great way to reduce any temp swings too.
Cool project, I've read about it many times but just have too many projects already.

 

[GreyRaven]

I'm actually running a test aquaponics system at home until we move to a new house, when I want to go for a system in the 1000 gallon range. (I dream of being as close to self-sufficient as possible)
I have seen a video on YouTube in which a retired electrical engineer fully automated his setup using Arduino controllers with PIDs to control the various valves and the heater. If I can locate the link, I'll update.
I use a BrewPi setup to control my fermentation chamber and have been pondering the ways that it could be adapted to control aquaponics. I like the combination of a Raspberry Pi to provide the Web server and remote administration, linked to an Arduino to control the control devices. I have yet to find ready made software to do the automation, but I know that it is possible.

 

[DaveMcPhee]

I'm actually running a test aquaponics system at home until we move to a new house, when I want to go for a system in the 1000 gallon range. (I dream of being as close to self-sufficient as possible)
I have seen a video on YouTube in which a retired electrical engineer fully automated his setup using Arduino controllers with PIDs to control the various valves and the heater. If I can locate the link, I'll update.
I use a BrewPi setup to control my fermentation chamber and have been pondering the ways that it could be adapted to control aquaponics. I like the combination of a Raspberry Pi to provide the Web server and remote administration, linked to an Arduino to control the control devices. I have yet to find ready made software to do the automation, but I know that it is possible.

hah, I'm actually hooking the PID controller up to a raspberry pi to monitor usage patterns. Not sure how yet, but once water temps are working, I'll get on that.

the great thing about AP systems is that there are no moving parts (if you want) apart from the always on pump. I always dreamed of building a full electrical brew system, but I knew the electronics where beyond me. This AP system is a great intro to a similar topic - finely controlling water temps electronically.

You're also lucky you live in washington, where it's cooler. A tank full of tilapia is great, but you have the option of trout ... jealous

 

[Konadog]

You could use, and adapt something we use in this hobby, or you could look for a controller for fish tanks, something from Digital Aquatics, Apex, etc.... that is made for that hobby, much easier.

I have a full blown system from Digital Aquatics that run my cooling, heating, all pumps, skimmers, lighting, etc..... on my 225 gallon salt water tank.

 

[GreyRaven]

I do have the option of trout, but it looked like I would need more in the way of permits to use them. I'd rather do tilapia if I can work out how to heat the water without using electricity from the grid. Ideally I'd use solar in some form, but solar in Western Washington is a bit of an oxymoron.