Reading absolute pressure with Bosch MAP sensor with Arduino #1 (actual measurements) 

No worries, just be careful with where in the code says HASH it needs to be substituted with # and MORE_THAN and LESS_THAN with >= and

You are welcome :-)

Hi ademir, it should work with any map sensor, as long as it is 5V and you know wht the different wires output.

You need to update the linear model formula. First get the pdf of the sensor and see my video 2 after that one with the maths. If you still do not understand it, let me know and I can tell you what to change in the code.

Hi Nicholas, absolutely agree that these should be done for better and more accurate measurements. It was just that I wanted something quick to measure the crankcase pressure in my car. I can of achieved that with multiple measurements to smooth the signal. Thank you again for the great suggestion and comment.

@palomban @moremolecules Can you explain where to put the resister and cap (with values)? As you can tell from my avatar I have a 1971 Plymouth 'cuda. I'm working on a data logger to help accurately tune the carburetor. One of the items I need is vacuum. I figure using this will give pressure in the intake manifold and then use either another to open air or a DPS310 to measure pressure and altitude. Then subtract the pressures and / 33.8639 to convert result to in Hg. I know this is 3 years old but hoping you will reply.

There is a pdf manual for that bosch map sensor (e.g. here: secu-3.org/wordpress/wp-content/uploads/pdf/bosch_map_sensor_technical_specification.pdf), but pin 1 and it should be written 1 on the sensor is the +, pin 2 is the negative and pin 3 is the voltage output. The voltage output is the one that can be read with the arduino and one can calculate the air pressure from the voltage that is coming out.

@@moremolecules Thank you so much! I looked at another bosch manual for map sensors and pins 1 and 3 were swapped, I’m afraid I have broken the sensor by following the wrong manual….

@@monkeeee7945 I might be wrong, but I do not think you can damage it with dwapping the +feed with the output voltage. Probbaly you can, but try them the other way around and see if it give any readings.

Many thanks indeed mike, much appreciated!

I was thinking of using this sensor to measure more accurately the crankcase pressure in my engine, following the oil catch can. Unfortunately, I did not think about that it measures absolute pressure and with change in atmospheric conditions my measurements will not be entirely accurate. I have another sensor that I can use. I will post once I get some measurements, as I was thinking of second oil catch can, so I was not too sure how much more the pressure will be, hence the sensor. This one is used to measure the manifold absolute pressure in the throttle body and in conjunction with the MAF sensor send information to the ECU about how much air goes through. Basically, how much boost the turbo generates, if I am not mistaken.

@@moremolecules so, this sensor is located between the intercooler and the intake, and meassures the boost that the turbo blows. My motor is getting worse, i had to take out the catch can to let out free the pression in the crankcase, because started to leak oil though the turbo.

@@dieseltips Hi mate, I am really sorry to hear about the oil leak. Where does it come from? Is it increased crankcase pressure and then the turbo oil outlet cannot drain into the crankcase? The strainer could be partially blocked on the oil return from the turbo. Good luck.

@@moremolecules the oil comes from inside of the turbo, I had arranged the outlet of the gases and without the catch can the hose blows free to the back of the car, so now I dont see more oil smoke like it was before. I think the oil retourning back from the turbo to the block now that the pressure is going out. Thanks for your videos.

@@dieseltips Yes, as you say, most likely the return strainer is partially blocked. This is fairly serious and you may want to check the strainer on the turbo return. If the strainer is blocked, it means that the turbo does not have fresh oil coming in to cool it down and could overheat and fail. I presume that the oil is not overfilled, this may lead to the same effect.

Hi Frank, as I said in the code below, LESS_THAN is to be substituted throughout the whole code. It is just that RU-vid does not allow the symbol > and < in the description. So substitute LESS_THAN or MORE_THAN with < and >

Sorry didn`t seen that part. going to try yours aswell. This is my version to read the mapsensor: /* Mapping example connectors: 1 = sensor 2 = gnd 3 = 5volt Re-map a number from one range to another. */ int Value; // store the value coming from the sensor float mapped; // store the new value void setup() { Serial.begin(9600); while(!Serial); } void loop() { Value = analogRead(A0); // map(value, Min Sensor, Max Sensor, Min range, Max range) mapped = map(Value, 672, 144, 0, -8); mapped = mapped / 10; Serial.println(mapped); // wait for 1000 milliseconds ( 1 second ) to read every second delay(1000); }

@@franksmit4914 The mapping is the important bit, but I found that depending on where you use this sensor it may need a bit of averaging/smoothing of the signal. That is why I have the averaging of multiple signal readings. Good luck

Hi Gregory, depends on the type of iphone. As far as I know only iphone6 and above have a barometer electronics inside, the previous models would not have it. Then you need any free app that access the barometer and can display the pressure. Hope this helps.

@@moremolecules it looked like it was an iOS system app...thanks, I found one on the App Store.

Hi Alex, unfortunately no, I think I bought it second hand from ebay.

@@moremolecules ta anyways, the code will be very helpful to get this going!

@@alexjohnston4872 Depending on the purpose, any of these should work. IMHO Bosch produce a variety of these with different codes, although the specs might be sightly different

@@moremolecules Do you have a link? I have found a code I think its a Bosch 1 928 403 110 but seeing if I can find it assembled

@@alexjohnston4872 The exact one I had bought it does not exist anymore, but I dound a few that should be the same. For example this one (www.ebay.co.uk/itm/Bosch-MAP-Sensor-Manifold-Absolute-Air-Pressure-0281002593/173328596452). On another video I had with the differential pressure (2 spouts): www.ebay.co.uk/itm/Bosch-DPF-Exhaust-Pressure-Sensor-Diesel-Particulate-Filter-MAP-0281002772/173328594132. The bosch is a bit expensive, but others that are not branded are cheaper.

Hi Utku, it does not jump, it is the scaling of the arduino graphing software. Because it is MAP (absolute pressure) without sucking on it or pushing, it will measure the atmospheric pressure, which at my place is ~1,000mbar or 1atmosphere. It is just that when I sucked, it dropped, then it stabilises at the atmospheric pressure (1000mbar)

@@moremolecules I dont understand, How the pressure rises altough it is under vacuum ? Is the sensor is not airtight ? You suck air , momentarily the air pressure inside the sensor drops and shows 700. What I understand is, your hose connection from sensors port to syrine is not airtight. Is it correct ?

@@ytkdmr It was awhle ago, but I think it should have been air tight, but it might not have been. It was just simple tubing without anything holding it. There might have been an air leak and getting back to normal pressure.

It is in the description of the video! Only substitute more_than or less_than with > or

@@moremolecules Thank you

It should yes.