Room pressure monitor

Hello,

We are creating a biological confinement level 2 laboratory. We would like to measure the difference of atmospheric pressure between inside and outside of the laboratory since we need a negative pressure inside the lab. My main concern is the communication between the 2 sensors. It has to be in the air and it would be wonderful if it could record pressures for day or weeks. I need help to design the cheapest way to do it, the code and the wire connections. I have only little knowledge with arduino.

I think the BMP280 pressure sensor is fine and boards could be ArduinoNano with NRF24L01 radio transmitor modules and a cheap IIC I2C TWI 1602 16x2 Serial LCD.

Do you think it can works and anyone can help me please?

Thank you!

(deleted)

I've just calculated the parts which will cost about 10$USD. My goal is to have the lowest cost possible. I was looking for little help since I'm thinking that it is a very simple projet to make 2 boards communicate 1 data. Maybe I'm wrong?

(deleted)

How much time this kind of project can take to you?

biological confinement level 2 laboratory.

This is NOT appropriate for Arduino. You don't want this to fail on you with those sorts of consequences. Maybe use something a little more professional than a hobby microcontroller for kids to learn on.

Delta_G:
This is NOT appropriate for Arduino. You don’t want this to fail on you with those sorts of consequences. Maybe use something a little more professional than a hobby microcontroller for kids to learn on.

That’s just plain rude.

The Arduino is not just a toy, it’s a proper controller that has lots of real world applications beyond teaching and tinkering for which the Uno has indeed been designed - OP was talking about the Nano at least. The AVR family of controllers pre-dates the Arduino by quite some years. Now if you would comment on the level of competence of the OP vs. the expected level for such a biohazard lab, that’s another matter. The tiny budget available for this system is of course also at odds with setting up a bio lab.

OP didn’t however tell what the full application is: just secondary or tertiary monitoring of the main system, or at a more critical level. It appears to be just monitoring, there’s no mention of connection to other control systems, just a sideways suggestion of data logging.

The pressure sensors are fine, thsoe will do the job just fine.
The microcontrollers are perfectly reliable (when programmed correctly).
The NRF24 modules may not work when there are walls in the way. Maybe if there’s just a single thin wall, but in that case you can better string a wire through that wall (half a meter is no problem) and connect the second sensor on the other end, and read both from a single unit.

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I do not understand something: do not you need a certified device to do that kind of work?

I'm not concerned with the Arduino, but there are probably regulatory, safety, calibration, and quality control requirements that may be difficult to validate with anything that's one-of-a-kind or homemade. And, your compliance costs will make the component costs insignificant. :wink:

A wired connection is far more reliable than a wireless connection, and if you do go wireless you'll want something like Wi-Fi that's got error detection & correction.

And it should be serviceable, even if you are not around. I'd recommend extras of everything, including at least one Arduino that's programmed and ready to go. And, everything should plug-together or connect with screw terminals, etc., so nothing has be unsoldered-resoldered when something has to be replaced.

You cannot use the ATMEL micro-controller it is clearly stated on the data sheets that is it not for any sort of health care or life safety.

the Phillips sensors is NOT ACCEPTABLE in ANY way.

You have to use a true DIFFERENTIAL PRESSURE sensor that measures the pressures across the wall.
in the US, it is about 0.002 inches of water.
the BME280 is an absolute pressure sensor and the manufactures listed error is more than that.

the rule of thumb is that your sensor should be able to resolve 10 times more sensitive than your monitored point.
if you want to measure 0.03" you should be able to resolve to 0.003"

Pressure sensor
RMS Noise
Sensitivity Error
Temperature coefficient offset

0.2 Pa (equiv. to 1.7 cm)
± 0.25 % (equiv. to 1 m at 400 m height change)
±1.5 Pa/K (equiv. to ±12.6 cm at 1°C temperature change)

the noise is equal to 0.004" water that is your error starting point and is already at the critical point.

second, the BME is a single point, so you need one in each space and they would both have to be calibrated.
second, you would have to verity that the temperature of the sensor does not affect the reading. just one side getting warm could make the pressure invert.

Second, what is the worst case scenario of the pressures do invert ?
do you have contaminants infect the people inside of the room ?

do you force the contaminates to be expelled from the room ?

imagine if the researchers were a little more careful…
an estimated 36.9 million people are living with HIV today
I do not know if it was released by a simple reverse flow in a clean room, but there are other things that are more toxic.

When we did pharmaceutical production clean rooms, the cascade pressures from the exterior to the core area dropped as each level. an inversion of pressure would contaminate the entire facility. the one time there was an inversion it was due to a maintenance error and the re-certification along with the disposal of all the product was well over 500 mil. USD.

The research facility that had a similar accident is still patrolled with armed guards and when you gown up and enter, you sign that you know you will be shot and killed, then incinerated, if you violate the containment barriers. you get a tilt radio. in case you die inside and fall over, the radio tilts and alerts those outside where to get the body.

I would say that you do not need to monitor the pressure, but spend the money to create the proper air flows for the environment. the sensors are only there to document.

Lastly, the tubing that connects to both sides of the differential pressure transmitter are to be considered contaminated and a path that penetrated the theoretical barrier.

Go to a company that does this and is well staffed with qualified engineers.

make sure that the sensors you buy can be certified and calibrated with NIST traceable equipment.

As a note, here in New Jersey, we have more than a few Super-Fund sites that were making some really nasty stuff.
This is not casual engineering, nor the realm of hobbiests.

in my view it would be safer to tell a noob how to connect an Arduino to a 4,000 volt AC panel.

wvmarle:
That's just plain rude.

The Arduino is not just a toy, it's a proper controller that has lots of real world applications beyond teaching and tinkering for which the Uno has indeed been designed - OP was talking about the Nano at least. The AVR family of controllers pre-dates the Arduino by quite some years. Now if you would comment on the level of competence of the OP vs. the expected level for such a biohazard lab, that's another matter. The tiny budget available for this system is of course also at odds with setting up a bio lab.

OP didn't however tell what the full application is: just secondary or tertiary monitoring of the main system, or at a more critical level. It appears to be just monitoring, there's no mention of connection to other control systems, just a sideways suggestion of data logging.

The pressure sensors are fine, thsoe will do the job just fine.
The microcontrollers are perfectly reliable (when programmed correctly).
The NRF24 modules may not work when there are walls in the way. Maybe if there's just a single thin wall, but in that case you can better string a wire through that wall (half a meter is no problem) and connect the second sensor on the other end, and read both from a single unit.

How many BSL labs have you designed and certified? Ive done dozens. I know the regulations well. No, you can't design your own controller with an Arduino. That is totally inappropriate and could potentially get someone hurt or killed. Infectious disease is not something to play with.

Unless of course your plan is to try to go through the insanely expensive process of getting it certified in which case it will fail because of what is in the first line of #9. I can grab the quote directly from the datasheet if you'd like.

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