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I’ve put the Ladybug Shield together with other hardware and software to implement a kitchen farmer plant food adjuster.  For now I am calling this the “Ladybug Plant Food Adjuster.”  I am currently testing/using it in my home.

The home farmer will be growing lettuce, herbs, tomatoes… within their home,  likely the kitchen.  This is in contrast to the more expert hobby or professional that has “industrial capable” pH, EC – and other probes, honking LEDs,…i.e.: knows A LOT about growing vegetables and herbs and needs super fine control of plant food adjustment.

Thanks to Those That Went Before

It is difficult for me to imagine being able to build the Ladybug Shield (see previous posts) without Chris Gammell and Ryan (@SparkysWidgets).

  • Chris Gammell runs the exceptional Contextual Electronics courses.  While I pay for the privelege, it is indeed a priviledge to feel and be treated like an apprentice.  Besides shear learning in a supportive and peer environment, Chris’s 1:1 time has been valuable/insightful/amazing in shaping the design of the electronics of the Ladybug Shield.
  • Ryan open sourced his minipH and miniEC stamps.  I poured over Ryan’s design until I understood them.  I had no idea how a pH or EC meter worked.  Ryan’s work significantly simplified what I needed to learn and my approach.  ON TOP OF THAT, Ryan is a truly great and very helpful person.  Please support Ryan!
While there are many great companies, two have made a HUGE POSITIVE impact on this project:
  • OSH Park the most excellent producers of low volume (purple!) PCBs.  OSH Park has the most amazing support and personal service.  From the CEO (Laen) to the support person who took his efforts in helping me out to the next level (Dan) – if I must part with my money, there is no better company/service/group of folks.
  • Adafruit, providers of breadboards, all sorts of circuit creation “thingies” that are too cool not to buy, exceptional tutorials, libraries for chips (like the ADS1015 ADC I used on the Ladybug Shield) that work within the Arduino IDE, and terrific support on their forums.  EVERY post I have made has got a valuable response.  What a great company.  
Then there are podcasts, videos, and a slew of web pages that have willingly shared their knowledge.  A particular shout out goes to Elicia White, co-host of the Embedded.fm podcast.  She wrote a blog post on a question I asked that was very useful for me.  Now – there have been many more.  Elicia’s insightful answer is the most recent.

What The Ladybug Plant Food Adjuster Does

The Ladybug Plant Food Adjuster automatically adjusts the nutrient and pH level of a reservoir of water (the hydro part) feeding growing plants.  It is for people like me that enjoy fresh vegetables and herbs.  We have many reasons to supplement what we buy with what we grow in our kitchen.  While I garden both indoors and out, I live in an environment that does not support growing vegetables and herbs year round.  Besides, in the winter it is rainy and cold.  During the winter I don’t want to spend time in an outdoor garden but love being surrounded by healthy growing plants in my kitchen.

The Components

The Ladybug plant food adjuster consists of:

Ladybug plant food adjuster

  • The probe box:
    •  measures the pH and EC values in the reservoir of water being used to feed the plants.
    • communicates with the iPhone app (using BLE 4.0) updating the app with pH and EC measurements.  The iPhone app controls the probe box by setting what type and stage the plant is in (in the diagram above, the type of plant is tomato and the stage is Youth.  The type and stage set the values for the set points which will be used by the pumps to figure out if they are far enough away from the set point to add a dose of either pH adjustment or EC concentration).
    • communicates with the pumps (using wires) to turn on either the pH or nutrient pump if the readings are off too much from the set points.  It knows to add nutrients before pH adjustment since additional nutrients will change the pH level.  This is an example of “working smart for you.”
  • The pump box:
    • contains a pump to add nutrients and a pump to adjust the pH level.  It is controlled by the probe box (the “brains”)
  • The iPhone app (is currently really really ugly…but works on my iPhone and iPad.  The goal is to be functional for testing.  Design will follow function):
    • connects to the probe using BLE 4.0
    • gets info from the probe on what it is monitoring (plant type and stage) and whether the pumps are currently allowed to be pumping or should be off (regardless of the pH and nutrient level in the reservoir).  It uses this info to update the display
    • lets the grower set the name of the plant as well as the plant type and stage.
    • displays the most recent readings for pH and EC as well as the set points.  This way the grower can see if current measurements need to be adjusted
    • informs the probe whether to turn off or on pumping.  If pumping is turned off, the probe will not tell the pumps to turn on even if the measurements need adjustment.
    • lets the grower export then email the readings into a CSV file.

The Ladybug Plant Food Adjuster Hardware

Hardware includes an iPhone/iPad as well as the probe box and the pump box.

The Probe Box

Inside the probe box is an Arduino Uno with a Red Bear BLE shield and Ladybug shield attached to it.

IMG 3430

The schematics and layout (Kicad) are located at this GitHub repository.  Designing and implementing the shield was my way to learn electronics, making a PCB, the math / science / electronic design of pH and EC sensors.  It was – and continues to be – a very positive experience!   Please see the many earlier posts I have done detailing what I learned/what I ended up implementing and why.

IMG 3434

A pH and EC probe are attached to the Ladybug shield using the BNC connectors.

The back end has holes carved out for:

  • cable to 12V wall wart.  A 12V Wall wart powers both the pumps as well as the Arduino
  • the USB cable used by the Arduino.  This is optional.  I use it while debugging to print out to the serial monitor.
  • the wires that attach to each pump.

The Pump Box

The pump box contains two peristaltic pumps, one for adjusting the pH level and the other to adjust the nutrient level.  

IMG 3433

Wires – originating from the Probe Box connect the pumps to the Probe.  The Ladybug Shield uses the 12V wall wart to power the pumps.

How the Ladybug Plant Food Adjuster works

At the core of the Ladybug Plant Food Adjuster is the reservoir containing water with the nutrients set at the right pH level.  We start with a bucket.  It can be any bucket.  For now I’m using Rubbermaid.

IMG 3443


One of the Rubbermaid Buckets I Use

 But I have bought much nicer looking reservoir/hydro systems.

IMG 3442

Nicer Looking Bucket Growing Basil on Kitchen Counter


 My goal is to evolve into happy designs that please the grower.  Right now I am at the “Frankenstein” phase.   While single plant setups are “easy”, each would take its own Ladybug Plant Food Adjuster.  I will start using the Adjuster to grow about 6-12 heads of lettuce.  

I fill the bucket up with filtered water.  The less minerals/salts the better since the amount of nutrients is a measurement of the conductivity of the salts in the water (discussed perhaps more than you wish in previous posts).

I add an air stone to increase the amount of dissolved oxygen.  After all, plants need to breathe.  

Next, I attach a pH and EC probe to the Probe box and place the probes into the filtered water.

It’s time to mix up the pH and nutrient concentrations that the Pump Box will add to the filtered water until the EC and pH values are at healthy levels for the plant type and stage (of life).

Plant Food

I’ll use the term “plant food” when referring to the nutrient concentration.  Once the plant food is available for pumping, the Ladybug Plant Food iPhone app sets the recommended levels for the pH and EC.  The (yah – I know – extremely ugly…) setup screen of the iPhone app uses a UIPickerView to let the grower tell the Ladybug Plant Food Adjuster what type and stage the plant(s).

Ladybug app settings screen

The Settings Display of the iPhone app

  The image shows “Tomato/Youth” – this tells the Adjuster what the pH and EC levels should be.

As an example, here is my tomato/youth plant I am growing.  We call it/him/her? Tommy.

IMG 3440

Tommy Doesn’t Know What Day it is

What the “right” food is to feed a plant is based not only on scientific reasoning  but also what works best for you and how much you are willing to pay.  I started off using liquid fertilizers like the one I linked to from Amazon (if you click on the link and buy something I get an Associates fee – what the heck, that’s why this ad prominently placed below): 


As my knowledge evolved, I started using the product and advice from Hydro-Gardens.  The site has information on food and additional chemical compounds as well as the amount for several vegetables.  For example, here is the “recipe” for growing tomatoes.  I got the dry ingredients and then mix up the amounts for whatever it is I am growing.

IMG 3441

Dry Ingredients I Mix together to Feed a Young Tomato Plant

Now that I have the mix I need for growing a young tomato, I put many (I put around 5) scoops into the container and fill the container with filtered water.  The pump’s nutrient feeder hose is stuck into the plant food.

IMG 3444


The Plant Food Container 

I will stick the nutrient feeder hose into.  It is challenging for me to get all the particles mixed well. I’ve tried integrating mixing into an exercise routine.  At some point I need to think of “best ways” to mix the plant food.  I’d also like a better suited container.  I had just finished the contents of a salsa container so it became the plant food container – at least for now.


The Ladybug app knows to adjust the nutrient level before adjusting the pH.  The additional nutrients will change the pH of the water.  Once the nutrient level has been reached, the Probe goes through adjusting the pH level.  In all cases that I have come across, the pH of the water needs to be adjusted down.  This is why I use only one pH dosing container.  Which also happened to have held salsa…hmmm…too much salsa?  Nah…never…

IMG 3445

the pH concentrate is about a tablespoon of pH DOWN with water.  The concentration of Hydronium ions – which is what is being added to lower the pH level – is very intense.  This is why I dilute from pH down.

There’s an App for That

I decided to talk to the reservoir through an iPhone app.  I use the iPhone and have a developer’s license.  The app uses Apple’s Core Bluetooth framework to talk via BLE 4 to the Probe Box.  The probe box sends whomever it is connected to (in this case my iPhone running the Ladybug app) updated measurements as well as the ability to turn pumping on/off as well as select the plant type and stage.  I envision in most cases leaving the pump state on and letting the Probe Box determine if more dosing is needed.

Ladybug app home screen

 Settings were discussed earlier – see the settings screen shot.

I wanted to evaluate the data so I added the ability to export and then send what has currently been logged in a data base.  I then use a spreadsheet program to take a step back and see how well feedback and adjustments are going.

That’s it.  The app has two screens.  

What’s Next

It is hard to describe the sense of joy I have coming this far.  I’m setting up a reservoir for 6-12 lettuce.  I’m off to get that going and to plant lettuce seeds.



THANK YOU for reading this far.

Please find many things to smile about.