WetSpot

Dudgeon · Dec 13, 2020

As part of the final Electronics project for my thesis I wanted to design a reef controller. Alas, I couldn't make the case for this to my tutor, he said this is insufficiently novel because there are many reef monitor and control packages already available. Instead I built a temperature control chamber for improving the quality of 3D prints when using a FFF printer.

That project is over now so I can start work on something I've wanted to work on for ages, a reef monitor / controller.

I'll probably update a lot on here, mainly with schematic snips as they develop. I'm 'borrowing' heavily from the open source community. If anyone wants to help me on my journey, I'd welcome the input. This project will be completely open source as well.

Wish me luck

Dudgeon · Dec 13, 2020

Current (2020_12_13) thinking is:

I know this is a little weird. I'm tight for space an hate seeing wires. So, I'd like to relocate as much of the electronics out of the tank and to a remote manifold. Something like the above with a control like the below:

Schematic:

Dudgeon · Dec 13, 2020

I was able to edit my posts earlier, but dont seem to be able to at the moment, oh well... here is the schematic in little blocks:

Dudgeon · Dec 13, 2020

Finding cheap 3-way solenoid valves is difficult, I'll opt for two instead.

metzer · Dec 13, 2020

Without going and pulling the data sheets on each IC, if you are making a production prototype board, I would recommend addding a few vias (through holes) on key locations so you can add jumpers during the testing phase. This is usually helpful even after the bread board mock ups. It would take allot of digging on the ICs to verify your design. Have you breadboarded it yet?

Dudgeon · Dec 13, 2020

metzer said:
Without going and pulling the data sheets on each IC, if you are making a production prototype board, I would recommend addding a few vias (through holes) on key locations so you can add jumpers during the testing phase. This is usually helpful even after the bread board mock ups. It would take allot of digging on the ICs to verify your design. Have you breadboarded it yet?

Still working out what I want. I'm waiting for a few bits then I'll try the pump control portion. I'll be testing each module individually. Good shout about test points, defo need to add many. Never thought of linking each module for testing purposes, that'll be very helpful, thank you

Dudgeon · Dec 16, 2020

my trial module arrived yesterday, I had fun populating it. This is a pump control board which will be part od the greater system later on. I'd ordered this before @metzer suggested using the whole board with links for isolating sections. I'll be doing that next time. this morning I'll be testing it.

metzer · Dec 16, 2020

Your soldering skills look good

.

Dudgeon · Dec 16, 2020

metzer said:
Your soldering skills look good .

I won't win any prizes, but I'm ok with 0805. Haven't tested the pump monitor function yet, but the pump control works. I have found one error, I spec'd a 1W 0.5R for the current monitoring but changed my mind at the last second to use a 1/4W 0.5R but neglected to update the footprint (which is why I have that ugly mod). I'll hopefully be able to test the pump monitor tonight... Just got to write a little code first

metzer · Dec 16, 2020

You may want to add a small capacitor on the 5V output of your regulator. I have ran into problems with transients and "noise" riding in the 5V output.

Dudgeon · Dec 16, 2020

metzer said:
You may want to add a small capacitor on the 5V output of your regulator. I have ran into problems with transients and "noise" riding in the 5V output.

Thank you, I've shown the caps on the adc 5v line, it literally goes vreg, decouple, decouple, adc. Do I need more?

Silent · Dec 16, 2020

Thread definitely not what I was expecting.

metzer · Dec 16, 2020

Looking at your board traces, i assume the c3 may be acting as a filter cap on the output of the 5V regulator. It shouldn't couple with IC2 but if you start getting harmonics, may be something to check out as you trouble shoot.

Dudgeon · Dec 16, 2020

metzer said:
Looking at your board traces, i assume the c3 may be acting as a filter cap on the output of the 5V regulator. It shouldn't couple with IC2 but if you start getting harmonics, may be something to check out as you trouble shoot.

Cheers mate, I spose I'll know tonight. Defo something to bear in mind when I'm tearing my hair out!

Dudgeon · Jan 10, 2021

With your help I successfully designed and built a functional pump control PCB in which a digital input (from a pi) switches the pump on and off and an ADC outputs the pump current draw to the pi for monitoring it's health.

The next generation builds on V0 but now has a dock for the Pi and powers this with a protected 5V. It also controls two relays for external solenoids, monitors two float switches, includes some signal conditioning for a pair of conductivity sensors and has a temperature sensor input. V1 has now gone to JLCPCB for fabrication.

While I wait for V1 to arrive, I need to start thinking about the next gen. I've had second thoughts about the solenoid control, I don't think it's quite as streamlined as I'd have liked to power the solenoids externally.

My functionality shopping list at the moment is:

Pi dock and 5V power - proved in V1
ORP, pH sensors - proved in V1
Salinity sensor - V2 shouldn't pose much of a challenge if the ORP and pH probes from V1 work out
Temperature sensor - V2 ( should be fine if V1 temp sens functionality works)
6 switched 12V low current supplies (with health monitoring) - V2 ( should be fine V0 pump monitor and control worked, but will need a bigger ADC)
1. Autofeeder
2. 2 x peristaltic pumps
3. 2 x solenoid (for switching in auto water top off and sample pump functionality
4. Water pump (for drawing water samples or RO dependent on the solenoid states)
A mains switching relay - for temperature control - V2 (derisked by the solenoid relays in V1)
Mains power to 12VDC - Probs V3 or later simply because I don't yet know the final power requirement of this Frankenstein project

I'm a little skeptical about the salinity sensor, may not implement it.

Thoughts? Anyone? Features I'm missing?

Dudgeon · Jan 11, 2021

I'll also add a hole and mounting points to the hat for a pi fan

Dudgeon · Apr 4, 2021

My auto top-off failed the other day. This was a 3 float high street system and I woke to find my tank overflowing and the contents of my RO barrel on the floor of my kitchen. I tore the floats down and tested them, one was stuck so I messed about with it for a bit then it returned to operational, so I hooked it all back up and gave it another chance.

The system failed again a few weeks later in a similar manner. So, I've been manually topping the tank up recently (no more sleepless nights for me). The problem is that I'm not brilliant at remembering to top the system up, so the system has been anything but stable recently. So I knocked out a simple auto top off system I felt I could rely on.

This is an arduino nano with an inductor sensor on the RO barrel and an optical sensor on the tank. I wanted two inductive sensors but found out (too late for this system) that the inductive sensors are no good with glass. So, I have a couple of resistors on the optical sensor, but it works great.

Essentially, there is a pump manual button that I can use to drive water... manually.. if needs be.
There are 3 led's: one shows the system has power, the second shows when the pump is running and the third is used for fault indication.
I have two inputs (inductive and optical sensor) and two outputs, one for the pump and one for a horn to sound if a fault occurs. If the RO is low the horn and lamp give morse code for RO, if the water level and RO are low I get morse code for TL and if the pump runs for too long or too many times in a period, I assume something is wrong and an SOS fault is triggered. No more wet floors for me.

Being an optical sensor I'll need to clean it every week, but otherwise I think it's a pretty good platform. It has now been running perfectly for the past 3 days, but I have a few changes to make on the next generation.

The PCB has been ordered for 0.1 but these are the changes I'm introducing:
1. All inputs and outputs are changing from 2 terminal phoenix blocks. The sensors will be JST connectors , the pump and power will be barrel jacks.

2. Connectors were on the left bottom and right of the PCB, I've moved all of them to the bottom.

3. The horn was remote from the PCB as a stand alone unit, the new horn will be onboard (keeps the system tidy).

4. I've added a system on/off push button so I don't need to unplug it or reach for the socket power switch.

5. I've added two 4-position rotary switches, one to change between pump on times and the other to change the number of permissible pump cycles before a fault is thrown. I'll also use one of these settings for a water change mode (no faults for extended pump on period).

6. I've replaced the transistors with much smaller surface mount components, less pcb space and looks nicer. (the foot prints for the THT ones were also wrong which resulted in some creative fittings)

7. I've removed some pullup resistors as they weren't necessary.

8. The diode footprints were reversed... oh how I lol'd when I noticed how hot they were getting.

I'll be trying this out when the PCB arrives from China. No doubt there will be a version 0.3, but I'm enjoying the process so much that I don't mind going around the loop a few times anyway.

I know this is a little distraction from the Pi project, but the best projects start small and build as the need arises.