DIY Trace Elements Doser

[Borat]

In this thread I am going to teach your superior Kazakh engineering skills, specifically how you can build your own doser..

 

[Borat]

As I am running multiple projects in parallel, including upgrading some of my funky equipment with better built PCBs, I have already ordered and received a PCB from China for this doser project..

 

[Borat]

This PCB was designed using Fritzing software - which is an excellent software that makes this task an easy-peasy job for DIY newbies like myself...

 

[Borat]

I have also pre-ordered some peristaltic pump heads from China, it takes a few weeks to deliver them using specially trained donkey - but provided you are patient enough to wait, the price justifies it all (about 10$ per head)

 

[Borat]

The doser will be brutal-simple:
- there will be a rotary encoder with a small LCD screen where the user will be able to (i) specify dosing amount for each of the 3 dosing containers: frequency of dosing will be automatically decided by the software (ii) overwall volume of container (iii) reset the indicator that dosing container has been re-filled and (iv) calibrate each head.
- the doser will send daily email updates with the status of dosing containers/dosing amounts and, when dosing containers are about to become empty - warning emails as well..

The dosing containers will be plastic water bottles (500ml volume) and will simple be screwed into the dosing unit. That way the whole assemply will be a single piece with minimal tubing connectors.

The doser will sit above the sump (i.e. outside of electrics section) - for this reason the power supply (12v) will be external. This minimizes the hazard of high voltage use near water - this also allows for making the doser/head being very light.

The doser will automatically keep track of time using RTC chip and will also automatically synchronise the time using NTP protocol.

 

[Borat]

I start by cutting a 29.5cm x 8cm piece of 3mm acrylic (why 29.5cm? - it's because I buy pre-cut A4 size acrylic which is 29.5mm long):

 

[Borat]

I then use MS Word to accurately design the layout for Nema 11 motor holes. The layout is then printed and attached to the acrylic piece using frog tape. This allows me to drill holes accurately without using any other guides or measurements.

 

[Borat]

I am using the smallest Nema 11 (28mmx28mm) motors which are quite pricey compared to Nema 17.. They are however very small and their power is sufficient for this task where the speed of dosing is quite low (and thus high torque can be achived)..

 

[Borat]

After the holes were drilled (Nema 11 uses M2.5 screws - therefore the holes are 3mm diameter), the stepper motors are screwed using short M2.5 mm screws:

 

[Uncle99]

Interesting, but I could not do that.
I spent the $88.00 for the Jebao, still running 5 years.
But very interesting.

 

[Borat]

I then mount the stepper motor heads to the same assembly using 2x M3 screws:

 

[Borat]

Interesting, but I could not do that.
I spent the $88.00 for the Jebao, still running 5 years.
But very interesting.

I had Jebao - very good simple doser (I sold it later), however adjusting the dose is such a PITA! You need to go through the entier schedule and change every amount manually..

Also it's bulky and not something I was not very excited about.. I ran it successfully for about 2 years, then the power connector rusted (some leak spilled water over it) and I bought another one.. Then I built my own calcium reactor with a controller - and that made the doser redundant.. So the last 4 head Jebao found a new user for $30 US&A Bucks.. Jebao is very noisy! It's noisy because of the cheap construction of dosing heads..

Let me show you the amount of available space in my electrics cabinet - you can fit a small chicken egg somewhere provided your are inventive enough..

 

[Borat]

The new doser (in my specific example) will be dosing:
A- Elements,
K+ Elements and
Sodium Nitrate (my tank runs at 0 nitrates - therefore I have to dose Nitrates to keep my ATS/Refugium going and also to keep corals happy..)
..thus 3 heads should be sufficient for now.

 

[Borat]

Next step is to solder PCB components:
- Arduino Mega 2560 Mini
- ESP32 Dev
- Adafruit Logic Level Converter
- 12v to 5v voltage regulator
- 3x TMC2209 stepper motor drivers
- JST XH connectors for RTC, LCD and Rotary Encoder (all I2C - i.e. SCL/SDA)

 

[Borat]

Arduino Mega 2560 Mini is the same chip as Arduino Mega - except it's miniaturised and is PCB - friendly. It is sold unsoldered.

I use ESP32 Dev (as compared to other varieties of ESP) - for no obvious reason.. It's just a chip that I first bought a year ago to try - and now I simply buy the same one all over again..

 

[Borat]

PCB is complete now..

 

[Borat]

Gluing the box with Tensol 12...

 

[firechild]

Following along. I'd like to do something like this

 

[Borat]

The back cover will be held in place by a couple of small screws (TBD):





Now need to give the box a bit of resting time to allow all glue to fully cure...

 

[Borat]

I uploaded some existing code used for peristaltic pump (components are 100% same) - to test connections and also to ensure I haven't fried any electronics whilst soldering them..

Everything (including wifi connectivity) worked like magic.. Now I need to work on code to them test the motors in action...