Robo-Tank Isolated PH Circuit

[Rob F]

Probably going to order as soon as my paycheck comes in :D
Is it already implemented and tested in v5.02?

Btw does it work with jumperwires? Don’t have any USB Ports with I2C if I’m correct

Technically it's not added in v5.02 but I have the working code ready so it can be added quickly. There isn't anything to really test on the controller for the circuits functionality. The controller simply receives the pH from the circuit, if it works on one Arduino it'll work on any. For example if you setup a sketch to work with the circuit you would use the following line of code with the library I made.

float myPhVariable = ph.getPh();

With that the Arduino will have the pH in the myPhVariable and you can do whatever with it.

You can connect the circuit using jumperwires, those 8 headers on the board can also be used, one row of headers for Arduino to circuit and then the other row of headers if to connect multiple circuits together so you don't need to run a 2nd set of wires to the Arduino. Doesn't matter which row is input or output. The circuit can also be powered using 3.3v, 5v or 12v. The USB is 12v and the header pins are 3.3v/5v. If powered with 12v the onboard regulator will drop it down to 5v, if powered with 3.3v/5v the regulator is bypassed.

Will there be the possibility of having more than 4 USB in the future as well? I was thinking I would want 3 relay boxes and 2 pH probes.

There isn't a limit on ports, the only catch is another I2C buffer might be required. If you add to much wire/devices to an I2C bus it will overload and lock up.

The buffer I use puts out 1800pf, after mounted and connectors/traces my guess is its down to 1500pf. I'm guessing you use 6ft USB cables for each power bar, with those I guess your down to say 800pf. Add more cables with connectors and it'll drop again, once it gets too low problems happen so you need to amplify the I2C bus so it can handle more. Just plugging in a 100ft USB cable with nothing connected will likely lock up the I2C. These numbers are strictly guesses, and every setup will be different with the same connected because lots of variables involved. 

As I'm still unsure what this buffer can truly handle I only made a simple 4 port USB hub that does nothing but gives extra USB plugs. But I have my doubts all 4 could be used with 6ft of cable on each as that's a lot of connections. Eventually I will have a USB hub with a buffer and I'm thinking of adding a buffer / USB port on the power bar so you can plug something into it without needing a hub. Either way you won't have a problem running that and there's a good chance you can connect everything to the bus as is.