SparkFun Forums

[dschlic1]

I would like to get some help on a project I have been thinking about. Last year we built a pool in our backyard. Included in the package was an automatic controller and chlorinator. I want to add on to that controller to monitor the pH and the ORP of the pool water, and optionally adjust the chlorinator and perhaps dose acid.

I need some help in selecting the microcontroller and controller board. Ideally the unit should have:
2 analog inputs
LCD display
several user pushbuttons
one or better two serial ports, capable of 19,200 baud
optionally one or more relays
prototyping area to construct the necessary instrument amplifiers etc.
inexpensive or free development software. I will probably need to do floating point math.

The controller can be several boards, for example controller, display and prototyping. This is a one off project so I am looking at the lowest entry cost.

[lordsteve]

I recommend the Propeller microcontroller from Parallax. They have dev boards and examples of how to do analog-to-digital conversion with a resistor and a capacitor.

[Philba]

I would definitely not use capacitive discharge for ADC. While it does work, I would use a real ADC for accuracy. Lots of micros have ADCs built in.

take a look at this board - http://www.sparkfun.com/commerce/produc ... ucts_id=26

it's a little pricey but all you would need to do is add a PIC. You would need to get a programmer for it as well. I'm not sure what extra circuitry you would need but you could use a separate board for that. There are a number of similar boards if that one doesn't do it and you could even look at their schematic and use it as the basis of your design.


Another one to consider is the Arduino with the proto shield as a starting point.
http://www.sparkfun.com/commerce/produc ... cts_id=666
http://www.sparkfun.com/commerce/produc ... ts_id=7914

Sounds like a fun project.
Phil

[bigglez]

Greetings (No First Name Supplied),

I would like to get some help on a project I have been thinking about. Last year we built a pool in our backyard. Included in the package was an automatic controller and chlorinator. I want to add on to that controller to monitor the pH and the ORP of the pool water, and optionally adjust the chlorinator and perhaps dose acid.

I have been kicking around some electronics projects
ideas related to our swimming pool. I have a few
questions:

How do you plan to monitor the pH and chlorine
concentrations? (I presume using an electrometer.
What probes are you considering?).

How is your pool sanitized? (I presume by chlorine).
Are you using liquid or solid chlorine? What chemistry?
Does your chlorine source also include stabilizer
(cyanuric acid)?

Comments Welcome!

[saipan59]

I concur with Phil's recommendation of the SFE PIC board.
For a programmer, a PICKIT2 (from Microchip) is a great choice.
The PICs are cheaper direct from Microchip compared to most other sources. Order a PICKIT2 and 2 or 3 chips at the same time, thus meeting the minimum order and such.
Another option is to use one of Microchip's demo boards. They are expensive, but the advantage is that you'll have some working code examples that you can build upon.

Get MPLAB and the C18 compiler (student version) from Microchip (free downloads), and you're good to go.

There are several reasons to NOT recommend the Propeller for a general-purpose application like this, although I'm sure it could be made to work.

Pete

[dschlic1]

Bigglez: My pool uses a salt water chlorine generator. So I am going to use one of the comm ports to talk the the SWCG to adjust it's output. Part of this project will be to design and build the high impedance amplifiers necessary to amplify the mv signals from the pH and ORP probe. I am looking at some probes for sale on ebay. Total cost for two probes is about $75.

saipan59: I have looked at the PIC line, and also at the Arduino. However the computation involved with the project is pretty stiff, and would like a processor with some umpf and lots of memory. I am leaning to this item:
http://www.sparkfun.com/commerce/produc ... cts_id=259
it has just about everything but a prototyping area. I will need to add one to the back. Also while the chip has two UARTs, the receive data line for the second UART is being used for the pushbuttons.