Hello,
I would like to control by an app on my smartphone using Bluetooth a system composed by an air pump and a pressure sensor.
I don't really know where to begin..
if you have any steps suggestion 
and bestarduino products to buy for this project.
Thks in advance !
Durakuir
We need more information. To start, air pressure, volume versus time? Communication distance?
Read the forum guidelines for advice on asking questions.
Hi groundFungus,
Communication distance = Bluetooth range = for this project 3m is the maximum useful range
of course, it's a little more complicated but those are the main steps.
i don't know how to start.. find an air pump and an air sensor ? find the good arduino tool ?
Durakuir
What will the sensor be reading?
If you are going to measure gas in a cylinder, I'd use weight instead of measuring air pressure.
Controlling the air flow, I'd use a hot wire anemometer.
Snow levels, I'd use a bag filled with anti-freeze with an attached hose. The weight of the snow on the bag will send the antifreeze up the tube, changing the air pressure inside the tube in relation to the weight on the bag.
So, what you going to sense?
Also, from your description in post #2, you might consider a ESP32 or a ESP8266.
the sensor will be reading the air pressure.
I'm doing something very close int he idea to a tensiometer like
https://www.omron-healthcare.fr/en/blood-pressure-monitors/M2.html
From the description the code is not complex. But you have to define the hardware before you write the code.
You will need to pick a pump (compressor) that will supply the required volume of air (CFM) at the right pressure (PSI). Then you will need a motor driver to control the pump and a power supply for the pump motor.
You will need to pick a pressure sensor that will cover the range of pressures. The sensor interface method will need to be known (I2C, SPI, analog, digital).
Then you can start on the code.
If you want help choosing the hardware, we need to see numbers and hard data. And a detailed description of what you are doing. What are you inflating?
@GroundFungus thank you for your return.
I agree with you,i need first to build the hardware.
I am inflating a small flexible plastic pipe.
I realized several prototypes without electronic in order to determine that the maximum air pressure value I require is around 30kPa.
i have currently in front of me :
an air pump P53B01R from oken seiko VDC=6 ; Max Pressure = 85kPa; min Current = 180mA
https://okenseiko.com/en/wp-content/themes/oken_en/pdf/products/6_P53B01R_PDF.pdf
an air sensor 2SMPP-02 from Omron with a pressure range from 0 to 37 kPa https://www.mouser.fr/datasheet/2/307/en-2smpp-02-1128133.pdf
An arduino Yun
few battery AA
Speaking of air pressure, the pump and sensor are matching the requirement.
I'm trying to figure how to assemble all the parts together
Step by step :
make the pump working with only the battery AA
add the arduino yun and some code to start and turn off the pump
then add the sensor and collect the data with the arduino
i'm on step one, but my electricity knowledge doesn't look enough. I'm tring to put 4 battery AA in serial in order to have 6 V but i checked with a multimeter and it doesn't work..
"It doesn't work" is a poor description of the problem. It contains no usable information. What does happen? What voltage do you measure? How, exactly, are the batteries connected. Sometimes photos will help us to see what you are doing.
The pressure sensor output is only 31mV. That will need to be amplified to be read by an Arduino ADC. An I2C output sensor will be easier to interface. Look at this Mouser page.
Yes, one would expect close to 6V unless one of more of the batteries is bad or the motor is pulling more current than the batteries can supply.
Try with 4 new batteries.
What is the voltage with no load (motor disconnected) on the battery pack?
with no load the voltage on the battery pack is 0.33 when multimetre is on "20V" continue
when I check one battery, i have 0.15 .. i will buy tomorrow few new one ! (otherwise it's my multimeter or my use of it 
)
So, i just passed the first step on my list.
Step by step :
make the pump working with only the battery AA
add the arduino yun and some code to start and turn off the pump
then add the sensor and collect the data with the arduino
for the next step "add the arduino yun and some code to start and turn off the pump", I just read that maybe my battery pack will not be able to power up the arduino yun. my goal is to have my device in stand alone on battery, so.. do i have to look for another arduino ? or a more powerful battery ?
what is your advice ?
I have no experience with the Yun. What is the Yun supply voltage?
What driver do you have for the motor (you cannot drive a motor with an Arduino output).
Maybe use a 5V power bank to power the Yun through the micro USB connector and the 6V battery pack just for the motor. It is always better to power the processor and sensors separately from the motor to avoid motor noise affecting the more sensitive components.
"Maybe use a 5V power bank to power the Yun through the micro USB connector and the 6V battery pack just for the motor. It is always better to power the processor and sensors separately from the motor to avoid motor noise affecting the more sensitive components."
Excellent,i will try that.
What do you mean by driver ? my first idea was to connect directly the pump to an output of the arduino. but there are only 3.3v or 5v , so it can not work like that.
I have no idea on how it should work..
An Arduino output cannot supply the current that the motor will need. The Arduino can switch the motor on or off or vary the motor speed through a driver that can supply the required current.
Since it is an air pump I am assuming that the motor only will turn in one direction. If so the driver can be a simple transistor with a flyback diode and 1 or 2 resistors (cap optional). Choose the transistor based on the stall current of the motor. The stall current can be several times the running current. To estimate the stall current, measure the motor winding resistance. Take several measurements rotating the motor a bit between readings. Use the lowest reading in the calculation. The estimated stall current is the motor supply voltage divided by the measured resistance.
Hello @GroundFungus,
thank you for your last reply, it took me almost 3 days to understand and learn more about transistor..
The current stall is 200mA so I bought a transistor 2N2219A with a current collector max of 800mA
Then i tried to figure how calculate the resistor between DIG OUT and the transistor
I was not sure how to proceed..
i found 185 Ohm
i used the datasheet ofthe transistor in order to find Beta = 50 and VBE=1.3 https://components101.com/sites/default/files/component_datasheet/2N2219%20Transistor%20Datasheet.PDF
is-it correct or.. ?
calculation.pdf (716 KB)
The base resistor value is not very critical. It mus the high enough value to limit the current from the digital output to less than the recommended maximum current from the pin (20mA for Uno, Nano, ...), but low enough in value to allow enough base current so that the transistor is saturated. 180 Ohms is a good choice because it does both.
ok,thank you for the confirmation.
I will try like that. let see what is going to happen
