Reef Angel Forum

I am working on the planning for a new project that will require 2 PH expansion modules on a Raspberry Pi. I have found TCA9548A breakout boards that allow 1 to 8 multiplexing of the I2C bus, so that should take care of the address conflict between the modules. The multiplexer also allows for mixed ...

See this thread (http://www.reefcentral.com/forums/showt ... ?t=2584508) on RC for ideas on how to directly connect a Gyre or Cross Flow pump with a simple 0-5V or 5V PWM interface which should work with the RA Jebao cable ... or so I would think.

Dennis

Just as a follow up, using the RA hardware from RPI/BBB (in this case ORP module) is great. As expected, you just need to create some interface classes to allow them to be read over I2C. Here is an example of the ORP class I created to allow the ORP module to be used. In the example I have hard code...

Awesome!! I will place the order when I get home tonight.

I have been creating graphs by having a webcam take a photo of a free standing (Milwaukee) controller every 5 minutes and then keying them into a spreadsheet for days now. This is going to be so much easier!!

Dennis

When you say libraries, you are referring to the RA libs in the head unit, not firmware in the module correct? That is assuming their is a uC in the module and it is not just a ADC -> I2C.

Dennis

Something just occurred to me, as I want to use the ORP probe for the purposes of tracking denitrification, is the RA ORP unit capable of reading negative ORP values? Surprising not many of the free standing controllers are able to be set to negative values, but I am not sure if this limitation appl...

Oh, I get it. It is electrically isolated, not logically isolated, so everything still needs its own unique I2C address. I as thinking it created separate I2C networks that you could multiplex. Well that is a non issue then.

Dennis

That is awesome Roberto. Do you remember the I2C switch part number so I can grab the datasheet to see what I am in for as far as interface code? My immediate need is for an ORP probe hooked to my BBB, so I will use that as a test case. So for just 1 module I could forego the expansion module for te...

After giving up in disgust on using Atlas Scientific probes on my RPI/BBB, it occurred to me that RA hardware should be able to be interfaced to an RPI/BBB over I2C. The Atlas probes lack galvanic isolation, and are not a good fit in the hostile environment of an aquarium because of it. They (Atlas)...

Heh, I just went and looked again at the photo posted of the controller on RC (http://www.reefcentral.com/forums/showp ... ostcount=7).

It looks like they are using a low pass filter to convert PWM to Analog for the VA line.

Dennis

Looks like a low pass filter would be able to do this. PWM --> Analog.

Dennis

Thanks for clearing that up Roberto.

I wonder if we could get a PWM port to provide an analog signal with the addition of some caps and resistors. Time to Google.

Dennis

That is great news. I have been trying to help the guys on RC do the investigative work remotely but with limited success so far.

Dennis

I am waiting for confirmation, but based on info from RC users for the pin that the VA line is connected to, it looks like a plain old 5V PWM signal. The 20 pin variants have PWM0 output on the pin this line is coming from and the chips are all 3V - 5.5V parts. I am checking for the part number on t...

I have been following the thread on RC, but no one with a pump so far has the electronics background to actually determine what the control signal is. If one of you guys get a pump, please put a scope on the VA line so we can see what it is actually using. At this point it could be 0-10V, 5V PWM, 10...

You need to open the relay box and remove the booster. If it is just one channel you need, you can use one of the ATO ports as output, but only one can output PWM signals. Is the booster on the PWM expansion a daughter card? I am wondering if it can be ordered as a 10V and changed to 5V support by ...

And the result of the test was ... PH unaffected with the ATO floats removed from the water. PH stayed at 7.98. Put the ATO platform back in the sump, the PH drops to 6.95 (or thereabouts).

So you are correct, stray voltage, but the ATO switches are somehow involved.

Dennis

Do you mean the epoxied joints or my soldered and double shrunk wrapped ones? The shrunk wrapped ones are not even in the sump. The cords are long enough that the yellow cables make it out of the sump before the joint. The epoxied joints are under water (or at least the HIGH one is), but that is una...

Just as a follow up to this. Today I noticed a steep drop in my PH. As it turned out, I am pretty sure it was caused by my ventilation fan in the room with the tank being off, but in the progress of checking everything I noticed that the the PH seemed to jump around when I manipulated the RA. This e...

I just ran into the float switch issue as well. I had just read this thread and checked my PH on the portal and noticed that it jumped up and down by.03 -.05 on every refresh. What I found was that the ATO High switch was on the threshold of ON and OFF. When the portal refresh would catch the switch...