Backyard Aquaponics
A place to discuss aquaponics

Hey, nobody suggested installing cpanel or webmin on the pi. It was just an example (and there are countless others, webmin being a better one) of adminstration interfaces written in php.

It was misleading to say LAMP "...will be your application and the way you automatically collect and report information". mdavid's just given a great example of getting a very useful application running with a few lines of shell script over ssh.

The (commonly used) ds18b20 probes don't need (or come with) software, you just insert a kernel module and read from a file. Really not that different to reading the internal temperature of the pi.

http://learn.adafruit.com/adafruits-ras ... ng/ds18b20

In the long run I like the one wire sensors concept but have questions. If I'm successful and comfortable, I'll add multiple one wire sensors as the CFO and finances permit.

For now I'm looking at a minimum of 3 waterproof temperature sensors.

One sensor for outside air temperature, one for greenhouse air temperature and at least one for fish tank temperature.

So I'm wondering how to string the "buss" wire. I'll probably use Cat5 for convenience sake. Right now I'm thinking the outside sensor is one direction from the Pi ( which is in the house) . The other sensors are a different direction from the Pi. So the "buss wire" will look like a "star" network configuration to the Pi.

Is that do able?

How many "legs" of the "star" are possible if any ?

How long can the "legs" be? Do the ends of the "buss" wires have to have termination of some kind or can they just end with a one wire sensor?

How are folks doing their multiple one wire sensors?

Hi Bob,

I've been looking at doing something similar... Currently I have a Raspberry Pi with an Arduino UNO connected. I had some issues initially with getting the Arduino IDE to run on the Raspberry PI.

I don't have a monitor or keyboard connected, I just remote desktop in. My plan is to have to UNO read things like PH and temps. Also to control when the backup pump comes on.

I haven't got very far on the Arduino side but have got afew things running on the PI that might interest you.

This is where I started.

http://n00blab.com/how-to-set-up-raspberry-pi-without-monitor/

Then installed something called "Cacti", which can display collected data such as temps (currently only have the internal temp of the Pi displaying.

http://n00blab.com/cacti-pi/

and this:

http://n00blab.com/correcting-cacti-timezone/

As this was all very new to me and followed the guides mindlessly I did have some issues with group settings that I had some help with.

I also have a PH probe and sheild that seems to work but I haven't got the calibration solution yet.

https://www.tindie.com/products/rezahussain/arduino-ph-shield-by-dormant-labs/

After buying my Arduino I found a possible alternative for field devices..

http://www.phidgets.com/index.php

Ahh also some other devices like flow meters:

http://www.seeedstudio.com/depot/sensors-gas-and-liquid-c-144_151.html
https://www.sparkfun.com/categories/23


Cheers,
Stu

You can add multiple 18B20's to the same data pin...I'm using GPIO 4. You only need one 4.7K resistor for the group.

apnea, that seeedstudio site rocks

There's some very cool stuff there.

Like this for instance

2KM Long Range RF link kits $14.50

very cool.

You probably read this already, but the FAQ has this to say:


I read somewhere else saying that in practice it can work though - but ymmv.

The faq goes on to recommend "using a device such as the DS2409
MicroLAN Coupler16 a 1-wire hub device, at the branch point".

So I finally got round to playing with my pi. And here are my results!



So far it's just two temperature sensors, but I'm pretty happy. I've attached them directly to the pi for now, but will probably introduce an arduino at some point and use it's ADC to measure some analogue sensors (yeah, I could just buy an adc but I already have a couple of arduinos).

I've also ordered a web cam, so that might be next on the list of things to try out. The only posts I've seen with video so far have been mjpeg; not great but that would do for me.

I've also added my name to the 'interested' list for the camera module, it's due to be released any time now, perhaps some tutorials on how to achieve better quality streaming video will come with the new module?

I've got light sensors (are the lights on), pressure sensors (to measure the depth of water in the tank) and a flow meter (is the pump working) still to play with. I've also got some relays (mechanical and solid state) so I might give pump and light control to the pi.

I'd really love to be able to measure some water parameters... (ph, DO etc). If anyone has any joy do report back!

[Edit: added screen shot, in case the site goes offline or something]

Pressure for water depth. For some reason, I've never considered that angle to check for water depth.

Good brain using!

Will it need an external atmospheric calibration measurement? This site suggests that 10cm of water gives 1.00992 ATM. i.e. 1% change - which is in the range of atmospheric variations.

http://www.calctool.org/CALC/other/games/depth_press

I've seen water pressure sensors that do so with an externally compensated air pressure sensor (so one side of the diaphragm is open to the atmosphere).

It's really clever how they do it, you just attach one side of the pressure sensor to the underside of a PVC endcap, and attach 1.5 metres or so of PVC to it. Then put the PVC pipe vertically in the water.

As the pipe is filled with air you end up with knowing the pressure of the water at the bottom of the water, while keeping your pressure sensor dry... Genius!

If you had to purchase a sensir , surely a ping sensor would be easier?

I got very reliable readings from mine with 5 ping average....

Sent from my GT-I9300 using Tapatalk 2

Thanks, but it's not my idea! It's a common method in homebrewing circles. The only issue they seem to have is that the air tube can fill with water, so most people attach a 'bubbler'. I figured this wouldn't be a problem since I'll have an air pump running anyway.



You mean something like this?


Gosh, they are cheap! at that price I've ordered a couple and will try them out at some point. Glad to hear you've had good experiences with these types of sensor.

My main concern is weatherproofing it. I imagine even in an indoor set up it'll be exposed to high humity and some splashes. For my outdoor system it's got the weather to contend with too. At that price it's worth experimenting with though!



Exactly! I went for an MPX5010DP (for roughly £9 each) as this is what most people use with the brewtroller (linked above). They come in all sorts of varieties, but this one is designed for differential pressure - leaving one end open to the atmosphere gives the type of reading you want for this sort of measurement.

The range is over about 1m depth, but I'm not sure if the resolution is going to be enough to get sensible data from a tank though - there are other models that will measure smaller depths but at higer resolution which might be more suitable for (basically) constant height tanks.

Now just to find some time to try them out...

Resistance would be a pretty easy level checker as well. A stainless steel earth wire running the full depth of the tank, then a series of progressively shorter ones each connected to a pic pin. 100% resistance = no water at that level.

Actually it is quite common in industry everywhere. We have a few DP cells here at work.

BW, i have thought about a few different ways using that kind of idea, or capacitance etc. The only problem i can think if is having biofilm growing on everything that is submerged messing with the reading