Todo: Explain I2C mode setup for Atlas Scientific PH & EC sensor boards

[ghost]

The build instructions probably ought to call special attention to putting the Atlas Scientific sensor circuit modules in I2C mode (see EZO pH Circuit datasheet pages 40-41 , and EZO EC Circuit datasheet pages 40-41).

As @spaghet discovered last night (see our forum discussion), the Atlas Scientific EZO pH circuit module can talk either I2C or TTL serial on its TX/RX pins, but TTL serial is the default. You have to do a manual configuration step to put the module into I2C mode. The EC module works the same way.

At minimum, having TTL serial on the I2C bus will interfere with I2C communication, but it seems like overloading IO pins and causing hardware damage might also be possible. I'm not an EE, but it seems like it would be bad for the the pH module's TX pin in TTL serial mode to drive the Arduino's SDA pin up to VCC while the Arduino's I2C master was trying to pull SDA down to GND.

@jakerye, I'm not sure if this is the right place to make an issue about documenting EE stuff. Is this within the scope of what you work on? Should I put this somewhere else?

[sp4ghet]

https://github.com/Spaghet/openag_pfc2/blob/master/instructions.md#set-electrical-components-into-proper-modes

It's actually written there, but maybe it needs some more clarification.

[ghost]

@Spaghet Oh... I see what you mean:

3. Set the Atlas Circuits into I2C Mode

I overlooked that. Maybe that's enough. Although, links and page numbers for I2C instructions in the datasheets would be useful. I'd be curious to hear from somebody with more of an EE background if they think hooking a TTL serial line to an I2C bus has any risk of causing hardware damage. If it does, then probably it would be good to include a warning about that.

[sp4ghet]

I accidentally did it and it's running ok, but we'll need to see if it's harmful if you do it for days.

[srkmurd]

Hi, I am having issues with the measurements by electrical conductivity sensor. Only when its in the calibration solution it gives the value of the calibration solution, for other solutions, its showing 0.00. Did anyone face a similar problem before?

[sp4ghet]

Maybe the EC is actually just 0? If it's showing the correct value in the calibration solution, the actual value being 0 makes sense to me.

have you added liquid fertilizer and it still shows 0? in that case there might be some issues.

[srkmurd]

As i said I added NACL in water which definitely makes it conductor. Similary i have a microalgae culture which has electrolyte. So E.C shouldnt be 0 in these solutions

On Fri, 21 Sep 2018, 7:21 PM Rikuo Hasegawa notifications@github.com wrote:

Maybe the EC is actually just 0? If it's showing the correct value in the calibration solution, the actual value being 0 makes sense to me.

have you added liquid fertilizer and it still shows 0? in that case there might be some issues.

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[sp4ghet]

Do you change anything else when you switch solutions? If it works at all at some point the software should be working...

[rrivera111]

is this solved`? I am having the same issue

[rrivera111]

@sp4ghet where you able to solve it?

[rrivera111]

it is solved for me, thanks

[srkmurd]

The issue remains as it is. When all sensors are placed in the same solution, there is interference resulting in incorrect readings such as spikes and pH as 14.00 when it is actually 8.xx. So how have you resolved this issue?

On Fri, 19 Oct 2018, 8:35 PM rrivera111 notifications@github.com wrote:

it is solved for me, thanks

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[catbarph]

@srkmurd Are you using a carrier board with electrical isolation? Interference between multiple aqueous sensor probes in the same tank is a common issue, and may be the cause of the behavior you are observing.

[srkmurd]

Hi James,

Thanks for your response. I am not using carrier board and was not aware of the cause of the problem. Do I have any other way to deal with this as I have already installed the sensor boards on a PCB?

On Sat, Oct 20, 2018 at 6:36 AM James Hauk notifications@github.com wrote:

@srkmurd https://github.com/srkmurd Are you using a carrier board with electrical isolation? Interference between multiple aqueous sensor probes in the same tank is a common issue, and may be the cause of the behavior you are observing.

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[rrivera111]

In my case I am using the tentacle board and work good so far, I had a connection issue.... I believe atlas scientific also provides an isolation board

[catbarph]

@srkmurd Can you share your design // how the sensor boards are installed on PCB?

[rrivera111]

I am using this board on top of the rpi https://www.whiteboxes.ch/shop/tentacle-t3-for-raspberry-pi/?v=1ee0bf89c5d1

[eyespoint]

I am using the same T3 with EZO circuits for Ph and EC. Ph works fine but I get 0 reading from EC. Electrical isilation is in place. Anyone else had this issue and resolved with success?

[rrivera111]

are you able to get the readings from the pH? can you share your connection diagram for the ec circuit board?