Project advice for Saltwater tank heater controller

[system]

Hi

i am looking for some help to build a controller. my son would love a project to make a controller of any type so i want to try something and have him do it.
background for project.
I am breeding clownfish and i have 12 pairs of clowns. and the eggs are laid on clay pots and then i rremove the pot from the parent tank into a 10g "hatching tank" that the hatchlings will live for a few weeks till they go thru metamorphosis and start turing into clownfish and get their color and stripes.

while they are living in this 10g tank for a few weeks i have a 100w heater in the tank and i need to remove water and add water to the tank to syphon crap from the bottom of top off with water due to evaporation. so with these issues and the fact that heaters are not very reliable and able to keep the temp rock solid to the specs i want.
i was wondering if its possible to use a LCD panel and make a controller to control several (4 to 10) different heaters in different tanks and operate and control the heaters seperatly. for example. i will have 3 tanks full of babies and each tank will have 1 heater and 1 probe. i want a controller to control the heaters seperatly and raise the temp or shut off the heater when the temp hits a specified temp setting.it would also need to be scalable to allow me to add more temp probes and heaters as i need.

is this possible? could someone help me with a list of parts to buy and where to make this? and also help with programming? i would be willing to pay for the programming, reasonable too. hehe
if its gonna cost me more than a few hundred, i could buy a reef controller and pay $60 for each controller from digital aquatics, or use a rano controller.
it would be cool to have a small box that i can just add componets and add a temp probe and plug in a heater and set the parameters and its done.
would it be easy to add a timer for lights to turn them on and off to? i know the reef keeper and a few other controllers use controllable sockets to plug lights into and other stuff.

if anyone has any questions please post here or email me at ericm0574@gmail.com

Thanks for reading.

ps, this might not be a 1 time deal either. there is a big market for controllers for peoples fish tanks especially saltwater. and i know a few breeders like myself that might be interested in a heater controller.

[dc42]

Yes, that's all possible with an Arduino. Some things you need to decide first:

1. How are you going to measure the temperatures. There are lots of temperature sensor chips available, but they are not waterproof. You will need to encapsulate them so as to make them waterproof. The LM35DZ is a popular choice where the temperature to be measured isn't below 2degC. The Arduino has 6 analog input pins, so without extra hardware you can monitor 6 temperature sensors. To monitor more than that, you need either an external ADC or an analog multiplexer.

2. How are you going to control the heaters. I assume they will be designed to work of AC mains. The best solution is to use solid state relays (SSRs). These can be driven direct from the Arduino. A cheaper solution is to use electromechanical relays, but you typically need to use a transistor, resistor and diode to drive these from an Arduino. You can buy ready-made relay boards that include these components. You need one Arduino digital output pin per relay or SSR.

3. How are you going to set the temperatures you want. I suggest using a rotary encoder in combination with the display. The encoder needs 2 digital input pins, preferably ones with interrupts (pins 2 and 3 on the Uno), plus an extra pin for the push button function if it has one.

4. LCD displays come in 2 types: serial and parallel. The parallel ones are cheaper but needs 6 pins to drive them (or 7 if you want to control the backlight). The serial ones need only 1 pin.

[Simpson_Jr]

I do guess your project is possible and probably for a reasonable price as well.
It may even be possible to add functions that checks/controls the amount of water (evaporation), light, a system to feed the fish, salinity of the water and an option to check/correct PH-levels may be possible as well. It may get a lot more expensive with so many functions, but probably still less as a commercial version.

One thing is quite important, you're working with living material and a controller should work perfectly 100 out of 100 days. Should a heater not turn off/on because of a programming or other error... fish may start swimming belly up.

It possible to create a multi-tank multifunction controller, but the more functions you add, the bigger the chance of an unintentional error. I'd keep the existing system in the same room just in case and start with the simplest functions on 1 fish-tank.

It's hard to tell which components you should buy, loads and loads are available for similar techniques. Part of building is learning, which is another good reason to start with 1 tank. Buying wrong components for one tank won't be a huge waste of money, buying wrong components for 10 tanks will.

Part of what you want is your son to build it... I don't know what he knows already about electronics and programming, it may be a nice idea to just start by buying him an arduino + starter-set. With a starter set he can do most basic things like reading a switch, check the level of light, turn on a few Leds, program a melody on a speaker, perhaps drive a motor, display text on an LCD etcetera.

Doing that he will learn a lot, get comfortable with micro-controllers and... the fish-tank project will be easier to do. You could of course hire a programmer/designer, but will your son learn a lot if you do ?

Besides arduino + starter-kit I'd also buy a breadboard, used to make a prototype of what you want. Beauty of it is that one can easily build a circuit without soldering and change the circuit as you like without ruining components (if built correctly). If the circuit doesn't work as you want or... you would like to build another project, one can easily take the components from the board and start all over again. Once the design works exactly as you want... one can solder the components on a PCB as permanent solution. Prototyping a project on PCB and changing it is much much more difficult and probably costs you loads of PCB/components.

Since you're working with a live stock and he's 12 year old I do guess I'd start as simple as possible. By using a temperature sensor and 3 leds he could for example start by checking the water temperature and... write a routine to light led 1 if it's too cold, light led 2 if the temp's OK and light Led 3 if it's too hot. Doing that he'll already have covered the most important part. Next may be to display the temperature on LCD and after that he could program a menu to set the min-max temperatures using buttons.

Since he will be building it I'd buy an arduino with removable microcontroller-Chip. If, while working, he follows all instructions and checks his designs an arduino won't break fast. But... I guess all people on this forum have made mistakes connecting the wires wrong or miscalculating a design. Everyone here probably has smelled that magic smoke more then once

Should that happen with an arduino with DIP- microcontroller IC, it won't be a big problem, one can easily take the chip out of its socket and replace it with a new one.

Should it happen to an Arduino with SMD-chip (Surface Mounted Device),
which are soldered on the PCB, chances are you'll need to buy a complete new arduino. SMD-chips can... be replaced by someone with good solder skills, but even then the chance will still be quite big replacing such a chip will ruin the PCB.

Personally I've got no fish, but did want to use several techniques often used by people with aquariums/reefs. While searching I noticed quite a lot of people with fish-tanks use arduino (and other microcontrollers) to control their tanks. Several people here do show/seek help for their projects, but outside this forum there's also a lot of info to be found.

I could of course advise you to buy an Arduino Uno, a ds18b20 temperature sensor (they're quite accurate and you could read 20 of 'm with just 1 microcontroller pin), the solid state relay is also a good one to control an AC-heater. In theory that's all you need for 1 tank if you would use a PC instead of an LCD+buttons to build your project, but I guess that's part 2 of the process. Knowing what you could expect, finding out what you really need and making it a success for your son seems most important now.

[system]

Thanks for the replies. my head is kinda spinning now, but i think i got the idea of what you both are saying. in heeding your warnings i want to keep it simple and just have it control the temps in several tanks. i want to use a temp probe in the tank and have it turn on a heater to a certain programmable setpoint then shut the heater off when the temp i met. really nothing more than that. i would like it scaleable to allow me to add additional temp probes and cockets to plug in heaters.
as for my 16yr old son helping out. i want him to be able to build it and i would like to ask someone for some help in programming it for me, being compensated for their time of course. i would like a LCD display that i can see the temps in each tank, or what each probe is reading.

there is a reef controller out there that is callled a reef angel that is run by arduino. im not sure it could be programmed to do this for me or not, cause it has some stuff in a package as well..
can anyone point me to which items that i would need to buy ti make this project?