from http://quick2wire.com/category/i2c/pygmy_giant wrote:There is some interesting ADC info on the PCF8591 here: http://quick2wire.com/category/i2c/
I spent quite a lot of time fiddling with this ADC a few months ago as did a few others on here. I think we all seemed to hit the same wall which was, although we could get the chip to communicate with the pi - when it came to trying to read a voltage and convert this to a digital value and pass to the pi via I2C - we just kept on getting the binary equivalent of "hello I've just been switched on" over and over again, despite multiple attempts in various different ways.The next I2C board we’ll be testing is based on the PCF8591 from nxp (formerly Phillips) [...]
The software for openreefs seems to be free, but all the hardware needed seems like it adds up. How much is it? You can get a Seneye monitor for a tank for between $110 to $190.stimac wrote:@AdvancedNewbie - It looks fantastic. The Web Interface looks super nice - simple and to the point. Would it be much work to add additional hardware like ORP probe, or solenoid control? Are your arduinos made for specific probes. Are you writing the software as well?
Also worth looking into is this project: http://www.openreefs.com/
It looks like it's one guy. He is planning on producing a very thorough aquarium automation system, however he is producing extras that must be paid for. I can understand the monetary drive to do so, but I think the finished hardware and software support/development is where a little money could be made.
Hi rleyden,rleyden wrote:Adding the sensors for an aquarium monitor need not be all that complicated or expensive.
I'm considering a hydroponic system controller which would include a similar group of sensors as well as pump and valve control. So far I've added a 1-wire temperature sensor and an analog humitidy sensor via MCP3008 analog to digital interface. This is running as parts of a webcam server while I consider the next steps.
The 1-wire temperature sensor was less than $3 relatively easy to set up following directions in another forum thread. The MCP3008 was also only a few $ from Adafruit which has an excellent tutorial.
(http://learn.adafruit.com/reading-a-ana ... -a-mcp3008)
I did invest in the Adafruit Pi plate ($16) which gives you an easier and more stable access to the GPIO pins.
Phidgets has a nice assortment of enviromental sensors including a low cost pH probe for $24.
( http://www.phidgets.com/products.php?category=6 )
pH probes(as well as oxygen probes) put out a mV range signal so you would need to build an instrument amplifier circuit or buy an adapter ($30-Phidgets).
I have a koi pond oxygen sensor with an attached meter which I bought for about $120, so it stand to reason the sensor by itself should be less. The probe isn't intended for continuous monitoring. The documentation implies that it can get easily fouled. So, you need to research that.
For my hydroponic garden I dream of adding ion specific sensor electrodes which would allow me to monitor/adjust ammonium, potassium, etc. Lab grade ion specific sensors are $300 and up, per ion. In theory, these could be built pretty cheaply but I haven't seriously pursued that yet.
itavor wrote:I'm working on one of these gizmos. I'm a bit farther along (at least in theory) and am going down a more custom route (fully custom-made software, custom interface electronics). My controller started as Arduino-based but grew up. I spent a lot of time looking at what other people have done in this field and have cherry-picked useful bits of circuitry for my controller.
I'm trying to stay simple and low cost - that means freshwater only, only the most useful and essential features (i.e. PH and TDS/EC sensors yes, oxygen sensor no, auto top-off no), and finding ways to repurpose cheap probes (for example, a pro TDS probe costs ten times more than a simple hand-held TDS meter, so I just have to break one of those meters up and figure out how to plug it into my controller).
I'm not posting anything more detailed yet, as I've been known to start and abandon hobby projects before. But if anyone is interested, the project will be open source and open hardware.
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