Sral's Aquarium and Reef Pi Build

Sral · May 2, 2022

We got my parents old aquarium to give junior a bit of usefull cinema and I get to implement it. I therefore get to play around with technology (especially Reef-Pi) as much as I like ^^
Thought I'd share the project with you and get some usefull input.

Sral · May 2, 2022

READ HERE
(since I can't edit the above)

We got my parents old aquarium to give junior a bit of usefull cinema and I get to implement it. I therefore get to play around with technology (especially Reef-Pi) as much as I like ^^
Thought I'd share the project with you and get some usefull input.

Current Status: Planning phase

non-english native speaker

lack in professional terminology

especially fish and plant names

MINT PhD student

basic background in electrics, programming and chemistry

enough knowledge to understand the project in theory

lack in practical knowledge, e.g. prone to forget protection on signal lines ^^

no aquarium-knowledge apart from a lot of youtube videos (JBL has a nice playlist)

Aquarium (present equipment)

all of this will probably be replaced in the next 1-2 years when we move

bumped up 200 l fresh-water aquarium

old 1000 l/h 18W no-name Filter pump (filter volume 9l, wil get new filter material)

old suction kit with skimmer (will get new tubes)

old oxygen pump
Planning
- Tropic Theme
  
  basically this template from JBL, since it fits our interests, scaled from 120l to 200l
  
  water values
  
  T ~ 25°C
  
  CH ~ 4-5 dCH
  
  ph < 7.0
  
  CO2 ~ 20mg/l
  
  medium fast growing plants (as far as I understand)
  
  Fish
  
  20-30 Neon tetra
  
  3 Cockatoo dwarf cichlid
  
  15-20 Golden pencil fish
  
  6-9 three line catfish (or similar)
  
  10-15 golden oto (or similar)
  
  Needed Equpiment
  
  Ground heater
  
  Lights (T5 mounts present, bit dimmable LED are prefered)
  
  inLine heater (300W)
  
  stream pump for the catfish
  
  permanent CO2 tester
  
  Discussion
  
  exchange golden oto for Bristle nose cat fish (we do kind of like the latter)
  
  Bristle noses are known to eat plants-> is that a concern with medium fast plants and fertilization ?
  
  BIO CO2 based on yeast
  
  I do like the challenge ^^
  
  plant will be regulateable
  
  5l cannister as CO2 plant
  
  will be fed slow stream of sugar solution drops
  
  sugar-supply will be shut on before morning and shut off before noon
  
  feeding mechanism: dosing Pump with Reef-Pi ?
  
  overpressure valve (adjusted to limit the CO2 supply if anything goes wrong)
  
  check valve
  
  2 x 0,5l washer bottles
  
  Inline reactor
  
  2 PET bottles, glued together back to back, filled with Bio-balls
  
  both end have the bottle cap with a 16/22mm hose connector
  
  water flows downwards, CO2 bubbles want to go up and stay inside until dissolved
  
  placed in filter inlet (straight line -> more flow)
  
  placed in filter outlet (needs curve -> less flow, but safer for the filter)
  
  Air quality monitor
  
  CO2 in air
  
  humidity
  
  preferably all of that logged in reef-pi
  
  not many accurate devices have an analog or digital interface for that
- Reef-Pi
  - I want a maximum of modularity to make a clean build
  - Based on the above Aquarium and Equipment Reef-Pi needs the following:
  - camera(s)
    
    quick view of aquarium
    
    could be used to read the digits of a CO2 sensor like here and here
    
    I2C or ADC
    
    pH-Measurement
    
    Temp-Measurement
    
    Conductivity Measurement (perfectionism, I like my data ^^)
    
    Air quality (like here)
    
    PWM
    
    Light (prob. dimmable LED with color)
    
    sugar-solution dosing
    
    fertilizer dosing
    
    non-essential
    
    AC equipment
    
    value logging
    
    values from manual water tests, for example
  - Discussion
    - the most expensive component
      
      Atlas Instruments has 2:
      
      70 $ Consumer Analogwith 0.1 accuracy
      
      analog isolator is an extra 26 $
      
      170 $ Lab Digitalwith 0.001 accuracy
      
      isolator included
      
      longer lifetime and recalibration cycle
      
      is the accuracy below 0.1 realy necessary ?
      
      one can measure hardness and CO2-level and therefore, eliminate the pH-probe's offset regularly ?
      
      both analog and digital measurement is very modular: can simply be plugged into one channel of the ADC or added to the I2C
      
      is isolation usefull here ?
      
      manual mentions that isolation improves accuracy
    - from the Adafruit guide:
      
      10$ with 0.5 °C accuracy, non isolated
      
      from Atlas instruments:
      
      39$ analog kit with 0.3 °C accuracy
      
      26 $ analog isolator
      
      how usefull is isolation here ?
      
      the digital version mentions that no isolation is necessary
      
      how usefull is the accuracy here ?
      
      inline heater takes care of regulating
      
      Atlas-Instruments component is more modular, can be plugged into one channel of the ADC
    - I'm a scientist, I like data ^^
      
      Atlas Instruments is >200 $, more than even pH !
      
      Seed Studio is much cheaper and also probably good enough
    - third-party devices:
      
      read display with the camera (has backlighted display)
      
      collect from a csv-file on a WiFi SD-card in the device
      
      measure with an I2C device
      
      much less accurate, doesn't have a 2nd channel for calibration
      
      I2C makes it very modular though, so maybe I'll just go with this
    - Not decided yet, prob. dimmable LED
      
      JBL offers a nice-ish system
      
      App-programmable controler with coloring and random weather effects
      
      ~600 $ (200 for each of: controller, main LED, color LED)
      
      not readily controllable by reef Pi
      
      4700 lum + color strip
      
      can probably get a lot cheaper and reef-Pi controllable
      
      [*]
    - afraid of dosing failure like here
      
      sugar solution dosing kind of needs to be adjusted to pH
      
      thinking about wiring dose pumps to Pi Pins and use the same speed from the Pi's PWM for all of them
      
      [*]
    - most Equipment handles itself or by PWM, no real AC needed
      
      value logging: available in the journal since reef-pi 5.0
      
      [*]

robsworld78 · May 3, 2022

Took me a while to realize those lists were collapsed.

For your probes the analog circuits aren't the best as you can get lots of noise over the analog wires affecting the output, if you go that route use well shielded cables and short lengths, it's better to have a long probe cable. The digital circuits are still analog but the analog stays on the circuit and the onboard MCU does the calculations and passes the data via I2C that's why they are better. Atlas circuits are very expensive and isolation is necessary for each circuit no matter what circuits you use. I have a pH circuit that's equivalent quality to Atlas pH and has the full isolation on the same board so don't need multiple pieces.

Robo-Tank Isolated pH Circuit for reef-pi

This is a precise, fully isolated pH circuit constructed using high quality components and is designed to integrate with the Robo-Tank aquarium controller. Don't have or need the controller, thatRobo-Tank Isolated pH Circuit for reef-pi - This is a precis

www.robo-tank.ca

If you go with Grove EC you will need the ADS1015 to get some analog inputs. It would be good (probably necessary) to add isolation to that using something like this, I should have something like that but don't at the moment. If you connect the ADS a few inches from EC circuit and then directly into the isolator noise should be limited. I have a feeling if multiple probes are connected to the same ADS they will interfere when in the same body of water as they won't be isolated so keep that in mind.

Gravity: Digital I2C Signal Isolator

Gravity: Digital Signal Isolator is capable of isolating I2C digital signal and providing isolated power to the sensor module, effectively preventing mutual interference between the sensor modules.

www.dfrobot.com

Another thing to think about is the number of I2C devices you connect, if you have too many you're going to have reliability issues, every cm of wire, trace, connector and device puts a load on the bus and it can only handle a small amount. Cable and connectors are the biggest factor and it's sounding like it could get messy quick. You mentioned that dosing issue, that could happen if you were using a pca9685 to drive the dosing circuit (hopefully @Ranjib can add that verification

) so it would be good to use a GPIO on the Pi instead. You can get extenders or buffers for I2C so look into getting one of these or similar, there are quite a few versions, this will help greatly.

Adafruit LTC4311 I2C Extender / Active Terminator

I2C stands for Inter-Integrated-Circuit communications, it's meant for short distances on a PCB or subassembly. But, hey, we're engineers, and we like to push the limits of ...

www.adafruit.com

Sral · May 4, 2022

@robsworld78 Thanks ! That's the the practical knowledge I'm definitely lacking

Is Isolation roughly done by:
- stabilizing input voltage with filters (capacitors) and a voltage reference ?
- decoupling signal lines with something like an optocoupler ?
- that prob works best with digital signals, as those don't care about amplitude
ADS (analog Digital Converter Circuit) Isolation is probably done the same:
- filter and stabilize input voltage (prob also done internally)
- optocouple the digital signal lines to the PI
ADS Interference probably somewhat depends on internal IC setup as well:
- somewhat highest for one ADC that samples all input channels by a multiplexer (colleague had that problem)
- somewhat lower for dedicated ADCs for each channel
- somewhat lowest for one ADC IC brick per channel isolated as above
I2C Extender:
- could that be done by a transimpedance amplifier with better slew-rates and/or higher current limit than the Pi pins ?

I'm currently thinking about implementing Modularity by having:

contains:

power supply

step down converters

Pi Zero

provides:

power lines

(currently thinking 4-pin AMP power connector,5V,GND,GND,12V)

common earth

extended I2C Interface over a shielded BNC or SMA connector

GPIO Pins

DSub with 8 channels

something like 3 pin connectors for single channels

PWM pins

for critical operation (dosers)

2 pin connector
contains:

ADS1015 IC or similar

provides:

ADC channels, each with:

5V only 4-pin AMP power connector

some signal connector (round Banana plug ?)

therefore takes analog sensor modules
contains:

pca9685 IC for uncritical operation (LEDs)

provides:

PWM channels, each with:

4-pin AMP connector

2 Pin connectors for each channel

That should give a clean system that's pleasing to the eye and probably complete crap on signal quality because I am running signal lines parallel to power lines

Sral · May 4, 2022

@robsworld78 Had a look at your reef-pi Hardware and saw that I probably have to go over the number of pins for each of the connections again. e.g. that I2C needs a shielded 3 wire arangement, two signal and one ground.

robsworld78 · May 4, 2022

Sounds like a good plan. Optocouplers are often used for isolation, they have an internal LED that keeps the circuit physically isolated. There's a lot of methods for isolation, I think it depends what you're isolating. Decoupling caps are important so any power spikes or drops can be dealt with. I'm sure there's many ways to build an I2C extender, I would just use one of the chips available as they have everything built in, typically just need some pullup resistors so easy to work with. A common ground to the Pi is necessary for the I2C circuits so yeah minimum 3 wires but you also need to get +5v to them so 4 wires or lots of power supplies.

Tankkeepers · May 4, 2022

Following as iv been wondering about reefpi for a long time

I have alot of experience with raspberry pi

Iv currently got 5 spares laying around

I use them to make robots good brains

I also made a small super computer using 50 of these awhile ago that was cool watching each pie act as a single thread prossesor

Man that thing was fast but alittle bit of a fire hazard lol

Sral · May 5, 2022

Tankkeepers said:
(...) I also made a small super computer using 50 of these awhile ago that was cool watching each pie act as a single thread prossesor

Man that thing was fast but alittle bit of a fire hazard lol

Reminds me of the professor that didn't get funding for his own computation cluster, so he bought 20 of the early PS3, installed LINUX on all of them and build his own cheap cluster with Ethernet and Airconditioning

robsworld78 said:
(...) I would just use one of the chips available as they have everything built in (...)

I'll probably do that. (premade Isolation chips)

robsworld78 said:
A common ground to the Pi is necessary for the I2C circuits so yeah minimum 3 wires but you also need to get +5v to them so 4 wires or lots of power supplies.

I'll probably give them a dedicated power cable from the main unit, where I run one of your 12V supplies and one or two step down converters (one dedicated to 5V for the Pi and one to 5V for the equipment. The 12V supply looks good and I'll get one of your pH circuits anyway. Went to my local Aquarium store today and bagged the last pH probe for 50$ together with other things ^^

Still thinking about whether I need 12V though or if 5V all over is enough. Less risk of failure. DC and stepper motors for dosers can run with 5V, relais can run with 5V, so why bother with 12 V ?

That would also make it a good idea to include 5V power in all extension cables to the modules like your robotank- > cleaner build.

robsworld78 · May 6, 2022

Sral said:
Reminds me of the professor that didn't get funding for his own computation cluster, so he bought 20 of the early PS3, installed LINUX on all of them and build his own cheap cluster with Ethernet and Airconditioning

I'll probably do that. (premade Isolation chips)

I'll probably give them a dedicated power cable from the main unit, where I run one of your 12V supplies and one or two step down converters (one dedicated to 5V for the Pi and one to 5V for the equipment. The 12V supply looks good and I'll get one of your pH circuits anyway. Went to my local Aquarium store today and bagged the last pH probe for 50$ together with other things ^^

Still thinking about whether I need 12V though or if 5V all over is enough. Less risk of failure. DC and stepper motors for dosers can run with 5V, relais can run with 5V, so why bother with 12 V ?

That would also make it a good idea to include 5V power in all extension cables to the modules like your robotank- > cleaner build.

I think it's just preference for 5v vs 12v. Personally I like 12v and regulators as some AC adapters don't have the greatest regulation and with 12v the power supply doesn't need to be so large but in the end it doesn't really matter.