/sci/ - Science & Math » Thread #11126136

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Anonymous Thu 07 Nov 22:14:22 2019 No.11126136 View Reply Original Report

Quoted By: >>11126159 >>11126194

Hey guys, /chem/ and /biotech/ reporting in, being a brainlet again with regards to anything computer and electrical.

I'm trying to design a bioreactor system using an Ardunio. All is going well, except for the entire system we have for the power supply. We have to use three different outlets to supply power to the air pump, heating element, and arduino, because trying to run the air pump and heating element from the same source via a relay was causing too high of a voltage demand and resulting in readings of -127 C on our thermometer, which is used by the Arduino. This, at least, is my understanding.

I would love to have it so there is a central power terminal of sorts, described by "?" in the attached diagram, and have that be the single plug. Is this a problem that can simply be solved by a power strip, or would we see similar issues? How do I avoid frying all of my equipment?

Thank you all.

Anonymous

Anonymous Thu 07 Nov 2019 22:22:08 No.11126159 Report

Quoted By:

>>11126136
More information:

Here is what the Arduino's function is:
1. Detect temperature in bioreactor solution
2. When the temperature reaches 37 C or higher, it shuts off the heating element (which is connected via a relay to the Arduino) until it drops below 37 C again (I intend on switching to a PID controller once everything else is figured out).
3. Display the temperature at any given point, in addition to the status of the heating element, on an LED screen.

Two common issues were seen when we integrated the pump and the heating element on the relay at once:
1. The LED display would begin to fritz and glitch out, becoming sometimes unreadable.
2. The thermometer reading would come up as -127 C around the times of these same glitches. This is obviously a problem.

We thought at first that the pump, using an electromagnetic motor, was creating a magnetic field that was interfering with the rest of the electronics. But this problem was not observed once we disconnected the motor and kept it in the same vicinity still.

The motor requires no programming--it should simply run as long as there is a power supply.

Anonymous

Anonymous Thu 07 Nov 2019 22:37:58 No.11126194 Report

Quoted By: >>11126203

>>11126136
You could maybe try checking PC PSU, they have 12V rails on top of 5V regulated supply with high amperages you could directly hook to arduino too. They should be able to power everything up.

Anonymous

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Anonymous Thu 07 Nov 2019 22:40:37 No.11126203 Report

Quoted By: >>11126242

>>11126194
Something like this?

Anonymous

Anonymous Thu 07 Nov 2019 22:56:18 No.11126242 Report

Quoted By:

>>11126203
https://www.electronics-tutorials ws/blog/convert-atx-psu-to-bench-supply.html
Those should apparently do but you might need to short a few cables and attach some resistors to stop the safeties. I was more thinking of it being ghetto option if you have one lying around. These are apparently their ratings for 12V
http://web2.murraystate edu/andy.batts/ps/PowerRatings.htm

Usually you would buy a power supply 120V - 12V like
https://www.alliedelec com/product/mean-well-usa/edr-120-12/70473598/
rated at least for 7A preferably more. Even if it says 1 output you can just use some ingenuity to connect them in parallel on common ground.
> be solved by a power strip
Power strip just connects more sockets in parallel to the main socket. I assume your problem with power supply was that it wasn't efficient enough (couldn't output about 7A at 12V). Other problem might be if there is too much of a voltage drop on your cable connections, which means those are too long and too thin.

Anonymous

Anonymous Thu 07 Nov 2019 23:37:15 No.11126317 Report

Quoted By: >>11126442

I'm a chemist writing a proposal (as a department requirement, not an actual one) for bioreactors. What outputs do you measure to monitor the system? I'm trying to write up an instrument that would measure volatiles over time with mass spec for quality assurance

Anonymous

Anonymous Fri 08 Nov 2019 00:29:19 No.11126442 Report

Quoted By:

>>11126317
The one I'm building is incredibly simple. It is only programmed to monitor temperature and keep it constant (around 37 C). The pump runs constantly to, of course, prevent the settling of microbes.

Do you have other recommendations that we may need to keep track of? I don't think a pH controller is necessary since it's going to be consistent and I don't expect anything to change with regards to that.

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