Pin out of pump boards

[nahanoo]

Dear Harrison Steel,

We plan to do some experiments which require specific pump control. I’m not the biggest fan of mingling with the app.py file because I had issues understanding threading and I2C communication.
My idea is to use a small board computer for every pump board. Then I can simply flash the control board with the pump pattern and it should do it’s job autonomously.
My goal is to write the software in circuitpython and use it for example on this cute board: https://www.adafruit.com/product/4900
If this works, the idea would be to have a simple python API which can easily control run time of every pump. Of course this development would take place open source if others are interested.
I would then use the Beaglebone and your software to measure OD fluorescence and other properties, but the pump control is done based on my software and mini board controllers.

I’m optimistic that this approach could work, because you use the I2C BUS control which has great hardware and software support. I figured that micro USB cable has little to do with USB bit is used to split the signals in SCL, SDA, GND, and 3V.
From the Gerber files I suspect following pin out from the pump board (top view):
– GND or unused?
– 3.3V
– GND or unused?
– SCL
– SCA

Is that assumption correct? I’m mainly not sure if understood which pins are used as GND. I’m sure about SCL and SCA and the power I can measure out.
Is there anything I need to watch out for? What input power do you suggest?

I’m curious to hear your feedback and whether you think this is a feasible approach. I would be also really happy if you could point out if there is something I need to pay attention to.

Best regards,

Eric

[harrison]

Hi Eric,
Interesting idea! In principle it could work, but I must say, I am not sure this approach will be easier than messing with app.py. Probably you WOULD have an easier time sitting down and understanding what app.py is up to with the pump control, then building upon that.
Nevertheless, the inputs to the pump board are:
-6V
-unused
-GND
-SCL
-SDA

So the main difference with what you wrote is the 6V input. This is the power used to actually run the pumps, and needs to be able to supply ~0.5A minimum since they generally draw quite a large current when they start turning. Thus, you would need to make whatever hardware system you propose to develop supply this current or it would not be able to run them at all. Currently there is a regulator inside the Chi.Bio reactor doing this…

I hope this helps – as I said IMO you would be better doing it using the existing hardware infrastructure and making your changes in code. Once you do understand how it works, it is not so difficult to make changes!

Best
Harrison

[nahanoo]

Hi Harrison,

Thanks a lot for this fast and useful reply. You are right, I need to consider if it’s worth getting into it or not.
What I like about my idea is that it would also allow us to make use of the pump boards independently from the chi.bio.
We usually don’t run many reactors simultaneously so we have a lot of spare pump boards. With independent control we could make use of the boards for other projects as well.

Since there is the voltage regulator on the pump board do you think for prototyping a lower input voltage would work as well? As long as enough current is available.

Best,
Eric

[harrison]

Hello,

The voltage reg on the pump board is only outputing 3.3V for the digital components. It is NOT regulating a 6V input for the pumps. That 6V comes in raw from the cable.

That said, making a 6V supply is not outrageously difficult so I imagine what you propose can work! Maybe it would get by with 5V input – the limiting factor is whether that is enough to get the pumps spinning (IMO it should be).

[Author]

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