What does a Barometric Pressure Sensor do for your engine?

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Choosing the right barometric pressure sensor

Now that we have a clearer understanding of barometric pressure sensors, here’s what you need to consider when in the market of buying one for yourself!

What to consider Explanation
Pressure Precision Higher pressure precision allow for better sensing accuracy and reliability. This results in a better, stable, and more accurate output.
Pressure and Temperature Range Higher pressure and temperature range allow for a wider range of sensingIf you require sensing at extreme temperatures/pressure, ensure that sensor you pick delivers the accuracy as well
Power consumption No one likes a sensor that consumes a large chunk of power, hence do consider those that consume lesser powerEnsure the sensor chosen meet your power requirements of your project as well.
Size of sensor Thankfully for most barometric pressure sensors, they are small in size, making it suitable for compact projects.
Price If you’re willing to splash the cash, there are high end barometric pressure sensors out there but may not provide the best bang for the buckSelecting one with the best cost-to-performance ratio is highly recommend for extra savings!

Video

Making Sense of Sensors: The MAF Sensor

Full name Mass Air Flow Sensor, it’s more commonly known as a MAF sensor, air meter or sometimes simply MAF. While it might have many names, it’s responsible for just one, but…

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Check Engine Light comes on

Another common symptom of a failed BAP sensor is an illuminated Check Engine Light. If the computer picks up on a problem with the BAP sensor or signal, it will illuminate the Check Engine Light to alert the driver that an issue has been detected.

BAP sensors are important components found on many modern engine management systems. While they are simple in nature because they operate using atmospheric pressure, they can be difficult to test. For this reason, if you suspect that your BAP sensor may be having a problem, or your Check Engine Light has come on, have the vehicle inspected by a professional technician, such as one from YourMechanic. They will be able to determine if your car needs a barometric sensor replacement, or make any other repairs that are appropriate.

How to replace a faulty MAP sensor

Replacing a bad MAP sensor varies by vehicle, so please consult the manufacturer’s service manual for instructions for any specific instructions. Once the faulty sensor has been removed, it’s a straight forward installation for the new part. 

  1. Locate the MAP sensor on the intake manifold, either next to or on the throttle body itself, or on the intake manifold. 
  2. Remove any screws or bolts holding the sensor in place.
  3. Disconnect the electrical connector. Note: Do not force removal as the connector may contain a locking tab that may need to be removed prior to unlatching the connector from the sensor.
  4. If applicable, detach the vacuum hose from the sensor. Note: It is recommended to replace the vacuum hose with a new hose when replacing the sensor.
  5. Compare the new and old sensors.
  6. If applicable, reconnect the vacuum hose.
  7. Reconnect the sensor electrical connector. 
  8. Reinstall any screws or bolts that hold the sensor in place.
  9. Double-check all connections to make sure everything is secured.

Note: Depending on the vehicle and if a trouble code was set, a diagnostic tool may be required to reset the check engine light.

Connecting the Hardware

In this example, we will communicate with the T5403 using the I2C interface. While there are connections for SPI, they are currently unsupported.

Connection Names

The T5403 Breakout Board breaks out eight connections from the IC. We traditionally call these connections “pins” because they come from the pins on the IC, but they are actually holes that you can solder wires or header pins to.

We’ll connect four of the eight pins on the board to your Arduino. The four pins you need are labeled GND, VCC, SCL, and SDA.

Connecting Headers to the Board

You can use any method you like to make your connections to the board. For this example, we’ll solder on a eight-pin length of male-male header strip, and use male-female jumper wires to connect the T5403 to your Arduino.

Solder a 8-pin length of male-male header to the board. You can solder it to either side. The bottom is more useful for breadboards, and the top is more useful for jumper wires.

Note that the T5403 is sensitive to moisture. When you’re done soldering, do not clean off the flux by rinsing the board in water or other fluids.

Connecting the Board to your Arduino

When you’re done soldering, connect the VCC, GND, SCL, and SDA pins to your Arduino. Different Arduino models use different pins for the I2C interface; use the following chart to determine where to plug everything in.

IMPORTANT: Connect the power pins (VCC and GND) ONLY to a 3.3V supply. Larger voltages will permanently damage the part. Note that because I2C uses open drain drivers, it is safe to connect the I2C pins (DA and CL) to an I2C port on a 5V microprocessor.

T5403 label Pin function Arduino connection
GND ground GND
VCC 3.3V power supply 3.3V
SDA I2C data Any pin labeled SDA, or:
Uno, Redboard, Pro / Pro Mini A4
Mega, Due 20
Leonardo, Pro Micro 2
SCL I2C clock Any pin labeled SCL, or:
Uno, Redboard, Pro / Pro Mini A5
Mega, Due 21
Leonardo, Pro Micro 3
MISO Unsupported Unsupported
Reset/&SS Device Reset Any I/O – Logic “LOW” to reset
SEL I2C/SPI mode select Any I/O – Logic “LOW” for SPI mode (Unsupported)
EOC End Of Conversion Interrupt Any I/O or interrupt enabled pin – Outputs “HIGH” when measurement is complete

Once you have the T5403 connected to your Arduino, we’re ready to play with the software.

Tips and Tricks

Things to Watch Out For

Give it the right voltage: The T5403 will operate on voltages from 1.7v to 3.6v. We recommend operating it at 3.3V. Never connect the “+” header to voltages higher than 3.6V!. Note that it is safe to connect the SCA and SDL pins to an I2C port on a 5V Arduino, as the pullup resistors on the T5403 board will keep the voltage below 3.6V.

Give it air: Remember that the T5403 needs access to ambient air to measure its pressure, so don’t put it in a sealed case. Providing a small vent hole should be adequate.

But not too much air: On the other hand, exposure to fast-moving air or wind can cause momentary pressure variations that will affect your readings. Shield the device from strong air currents.

Keep it cool: Because an accurate temperature reading is needed to measure the pressure, try not to expose the device to rapid temperature changes, and keep it away from nearby hot parts and other heat sources.

Keep it dry: The T5403 is sensitive to moisture. Don’t submerge it or allow it to contact liquid water.

Changing the Solder Jumper

Solder jumpers are closely-spaced pads on a printed circuit board that are covered by blobs of solder to create an electrical connection. The T5403 breakout board has one such jumper; you can remove the solder from these pads to break the connection and alter the function of the board.

To remove the solder from a solder jumper, cover it with solder wick, and carefully heat it with a soldering iron. When the solder melts, it will be absorbed by the wick. Remove the wick before the solder cools so it doesn’t stick to the pads. If you didn’t get all of the solder on the first pass, give it another try with a clean section of solder wick. When you’re done you should be able to see a broken connection between the pads. While doing this be careful not to overheat the board (let it cool off if you’re having problems), or the copper pads may lift from the board.

Disabling the I2C pullup resistors (SJ1)

The T5403 communicates with a host microcontroller via a communications standard called “I2C” (for Inter Integrated Circut). I2C uses two wires, usually labeled SCL (Serial Clock) and SDA (Serial Data). To function properly, I2C requires a pullup resistor on each of those lines. The T5403 board includes these resistors. They’re enabled by default, but you can disable them by clearing solder jumper.

I2C allows you to have multiple devices connected to the same two lines (collectively called a bus). The pullup resistors allow the bus to function, but you should only have one set of pullup resistors per bus.

If you have just one I2C device (such as the T5403 breakout board) connected to your microcontroller, the board is already set up properly. You don’t need to change anything.

However, if you wish to connect more than one device to the bus, you should ensure that there is only one set of pullup resistors enabled on the bus. You do this by disabling every set of pullup resistors except one. (It doesn’t matter where the enabled resistors live; they can be anywhere on the bus.)

To disable the I2C pullup resistors, remove all of the solder from the jumper. This jumper has three pads; be sure to separate all of the pads from each other. Remember that you’ll need to ensure that another set of pullup resistors are enabled somewhere on the I2C bus.

Note that you should not operate an I2C bus without pullup resistors, as the internal weak pull-up resistors in the Arduino will pull the bus to 5V, which may damage the T5403.

Using the EOC pin

The End of Conversion (EOC) pin is used to signal when the T5403 is finished taking a measurement. There is a waiting period to read a measurement from the device. This time varies with the measurement type and accuracy desired. The example code uses preset delays as stated in the data sheet.

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