School project car's tires' pressure measurement

hi, before starting I have to say I'm really noob about all this arduino, xbee and programming (but unfortunately I chose this project and I really need to do it), so I hope you can help me.

I'm doing a school project, its about measuring, monitoring and recording the car's tires' pressure like TPMS does (I don't know if it records the obtained data), I've been looking for some hardware to try to do it and the way I should do it, but I'm stuck at this point. I bought the following things and I don't know where to start:

5 Xbee S1 modules
4 Arduino Fio
4 MPX5500D (Pressure Sensor) the data sheet is uploaded to the post
4 li-ion batteries
1 real time clock module
1 micro sd shield
1 xbee explorer usb
1 xbee shield
1 arduino UNO R3
1 20x4 lcd serial enabled
1 car adapter usb power supply
4 TPMS spare valves http://www.amazon.com/Schrader-20008-Service-Cadillac-Chevrolet/dp/B002GYQXZO/ref=au_as_r?ie=UTF8&Make=Chevrolet|47&Model=Aveo|2418&Year=2010|2010&carId=003&n=15684181&newCar=1&s=automotive&vehicleType=automotive#

now I know that I should have bought the wireless sd shield instead of the micro sd shield and the xbee shield, but anyways if I need it I will buy it.

now the problems/questions I have is:

  • The parts I chose are correct for my project?
  • Should I change my 20x4 lcd to another type of output?? Maybe using the screen of a netbook, a laptop, or a tablet?
  • If I use a netbook, can I reduce the usage of hardware like I don't know maybe without using the arduino uno r3 and its shields??
  • Where I can find info about xbee, sending data, recording it, and displaying it.
  • How can I reduce the size of the project

About the pressure sensor:

The designing of this devicen which has to measure the tire pressure and send the data via wireless using xbee, this device has to go inside the tire like TPMS; I have bought some MPX5500D the data sheet its uploaded to the post.

And designed a circuit to measure that pressure (including a separate battery pack), but the size of the whole circuit/device including the xbee transmisor (including fio, and it's Li-ion battery) it's quite big, and today while I was looking for some help on the internet I found a device that certainly will reduce the size of the device:

Absolute Pressure and Temperature Sensor - BMP085

The BMP085 is a high-precision, ultra-low power barometric pressure sensor. It offers a measuring range of 300 to 1100 hPa with an absolute accuracy of +/- 0.03 hPa. The BMP085 is based on piezo-resistive technology for EMC robustness, high accuracy and linearity as well as long term stability. This sensor board supports two supply voltages modes: 1.8-3.3V and 4 to 5.5V (solder jumper selectable). It is designed to be connected directly to a micro-controller via the I_C bus; it has a build power regulator and I_C translator that allow you to use it with 5V applications without permanently damaging the component.... Features: -I_C interface with I_C translator for 5V signals compatibility -1.8 to 3.3V and 4V to 5.5V supply range (one at time, jumper selectable) -Wide barometric pressure range -Digital two wire (I_C) interface -Flexible supply voltage range -Ultra-low power consumption -Low noise measurement -Fully calibrated -Temperature measurement included

http://www.alpha-crucis.com/en/drone-accessories/2905-absolute-pressure-and-temperature-sensor-bmp085-3700386988479.html.

So my question is: Is there any pressure sensor like the BMP085 that fits perfectly for my device??
Another question: If there´s no other sensor, the one I chose is able to work fine inside the tire??

I really hope you can help me, at this time I'm blocked.
Pleeaase heeelp meee =( =(

mpx5500.pdf (89.7 KB)

Others will have to answer your question about the sensor selection. Here just another thought: I think it was on Car Talk that they discussed how some car manufacturers measure the tire pressure to control a warning light in the dashboard. Turns out they are measuring the RPM of each wheel, and differences are traced back to the varying diameter of each wheel depending on tire pressure. Might be easier than sticking an Arduino into the wheel...

Holger

What do you plan to have on each wheel, Xbee, Fio, MPX5500D, li-ion battery plus assorted hardware?

That's a lot of stuff to be spinning around near the circumference of the rim. You could mount it near the hub and have a tube to the valve stem but I think that would mean no valve and there are some obvious safety issues with that. There might be a gadget that screws onto the valve stem and presses the valve pin to allow air to escape to your sensor.


Rob

What is your objective? I mean, are you just trying to build something that can be installed on a wheel and move around a bit at low speed to prove the concept, or are you trying to make something that can actually be used on a vehicle in normal daily use?

If it's only for a prototype used at low speed and over short distances, you should be able to get away with a UNO and shields inside the tyre as long as you are careful about mounting it. If it's for use under more realistic conditions I think you'd need to attach it to the hub rather than the tyre and that would impose some very tight packaging constraints so that it was still possible to mount the tyre. Any solution fitted inside the tyre is going to require an absolute pressure sensor rather than a relative sensor, and I don't know how hard they are to find or whether the sensor you're using is one. The only way I can see to use a relative sensor (i.e. sensing pressure difference relative to ambient) would be to put the sensor on the outside of the wheel - which might possibly be acceptable for a prototype of the wireless comms aspect of the problem, but is obviously not how you'd implement the final product.

thanks for answering!!!
shadowbrush said

Turns out they are measuring the RPM of each wheel, and differences are traced back to the varying diameter of each wheel depending on tire pressure. Might be easier than sticking an Arduino into the wheel...

Yes, it will be much easier, and that method its used by iTPMS (and I think if I cannot find any method to do it the way I have to do I'll try as you said: measuring the wheels rpm), but the problem I have is that I do have to develop it as I proposed to my school teacher, with data transmition via xbee and the sensor circuit inside the wheel

Topics merged.

DO NOT CROSS-POST, IT WASTES TIME.

hi, as Graynomad said

There might be a gadget that screws onto the valve stem and presses the valve pin to allow air to escape to your sensor

Indeed it has to be screwed to the valve, I bought some valves that are used for TPMS, they have a screw at the end that goes inside the wheel with the sensor and the transmitter, and mmm I think It's quite difficult to have a gadget to let my sensor measure the pressure being outside, it can fail and let the air goes out.

Answering to PeterH

something that can be installed on a wheel and move around a bit at low speed to prove the concept

yes, it's only to prove the concept, only a prototype for my school project that will be used for testings at a low speed and in a plain surface,
and about

UNO and shields inside the tyre as long as you are careful about mounting it

I guess it's quite smaller to use Arduino FIO

links related to Arduino FIO
http://arduino.cc/en/Main/ArduinoBoardFio
http://shop.sumeetinstruments.com/index.php?route=product/product&product_id=378

What is the pressure range? 2-3 BAR? BMP085 is not suitable as it measures 1BAR max. You have to measure temperature as well.

What is the pressure range? 2-3 BAR? BMP085 is not suitable as it measures 1BAR max. You have to measure temperature as well.

The pressure range is from 15 PSI to 75 PSI (±) that's why I chose the MPX5500D, but the sensor it's quite big and it requires a circuit and a power source, and the other BMP085 is not too big, and it has the circuit done and of course it needs a power source but it can work with the transmition circuit power source, that's why I was wondering if there's any other sensor like BMP085 that fits to my pressure range.

Psi?? :slight_smile: Ok, it is 5.2bar max.
The MPX5500 is relative (differential) sensor, so not suitable for your measurement as well..
Try to google "absolute pressure sensor 500kpa" or 75psi

Up to 150psi:
http://uk.mouser.com/pdfdocs/HoneywellHSC.pdf

pito:
Psi?? :slight_smile: Ok, it is 5.2bar max.
The MPX5500 is relative (differential) sensor, so not suitable for your measurement as well..
Try to google "absolute pressure sensor 500kpa" or 75psi

Up to 150psi:
http://uk.mouser.com/pdfdocs/HoneywellHSC.pdf

Absolute pressure sensor for measuring tire pressure? That tells you the pressure of the tire plus the atmospheric pressure at the elevation the tire is at. There are many uses for absolute pressure sensors but measuring tire pressure is not one of them.

A differential pressure sensor is the correct sensor where the high side port is seeing the internal tire pressure and the low side port is seeing atmospheric pressure, the resulting measurement would then be in PSIG (pounds per square inch gage) pressure, rather then PSIA pressure that an absolute pressure sensor measures. And that is the proper measurement units for tire pressure

Single port pressure sensors can be either differential or absolute types where in the case of the differential the low side port is internal to the sensor but still exposed to ambient pressure, where as the absolute pressure sensor has it's low side port evacuated (a vacuum pulled on it) and sealed from ambient pressure. Therefore all pressure sensors other then absolute pressure sensors are in fact differential pressure sensors, it's just a matter if the low side port is available to the user or not.

Lefty

@lefty:

Absolute pressure sensor for measuring tire pressure?

Yes, of course - for the school project YES. Shall he/she drill holes into the 4 wheels somewhere in order to measure differentially? :slight_smile: Why??
He/she can measure the atmospheric pressure with BMP085 at the master controller side while the absolute tire pressure will be measured by slaves (slaves will be simply put into the tires without drilling the holes). Mind it is a school project not a commercial stuff, read above..

retrolefty:
Absolute pressure sensor for measuring tire pressure? That tells you the pressure of the tire plus the atmospheric pressure at the elevation the tire is at. There are many uses for absolute pressure sensors but measuring tire pressure is not one of them.

It seems to me that an absolute pressure sensor would be necessary when measuring tyre pressure from inside the tyre, as proposed in this project.

One of the interesting issue I see with this nice project is how to switch the power (the battery) on/off of the 4 slaves while they are glued inside the tires :slight_smile: Or it will be "low-power" enough?

Do you remember back when something called a 'Glo-Yo' was fashionable?

something called a 'Glo-Yo'

UV light may cause skin cancer.. http://www.nottingham.ac.uk/news/pressreleases/2010/july/gloyo.aspx
Does it use an angular acceleration switch?
An Idea:

gloyo.jpg

shadowbrush:
Others will have to answer your question about the sensor selection. Here just another thought: I think it was on Car Talk that they discussed how some car manufacturers measure the tire pressure to control a warning light in the dashboard. Turns out they are measuring the RPM of each wheel, and differences are traced back to the varying diameter of each wheel depending on tire pressure. Might be easier than sticking an Arduino into the wheel...

Holger

That is how the low tire warning message on my 2000 Buick works. Turns out it's almost a 'free' measurement because there are already four wheel speed sensors as part of the antilock breaking systems so it only required additional software to develop the low tire pressure warning, no additional hardware needed.

Lefty

Tech background;-

Gas Law

PV = nRT

  • P is pressure
  • V is volume
  • n is the number of moles
  • R is the universal gas constant
  • T is temperature (K)

The sensors are in a Tire Pressure Monitoring System (TPMS)

  • Pressure, gas law
  • Acceleration, car speed
  • Temperature, gas law
  • Battery Voltage, battery management

The requirement of system;-

  • -40°C ~ +125°C full specified operation
  • Battery have to last longer than 5 years

Atmel solution;-

A low-power low frequency wake-up receiver for Tire Pressure sensor of battery power management.
315/434 MHz ASK/FSK UHF Transmitter.
125 KHz LF Receiver.

Infineon solution;-

Since 2003, more than 150 million TPMS sensors of Infineon continuously improved product generations were sold worldwide.

SP37 1300kPa Tire Pressure Sensor

SP37 1300kPa Tire Pressure Sensor

SP37 Development RF Kit is Available in two “flavors”

  • Operating frequency of 315 MHz or 433.92 MHz
  • Output power of 8dBm

Infineon only draws 4 sensors per car so do I, but my Lexus SUV's spare tire has one of those which make me lost a big face when light lit and I send it to dealer repair.

pito:
UV light may cause skin cancer.. http://www.nottingham.ac.uk/news/pressreleases/2010/july/gloyo.aspx

I'd never heard of that. No, the Glow-Yo I was thinking of was a Yo-Yo with a centrifugal switch which made the thing light up when it was spinning fast enough.

retrolefty:
That is how the low tire warning message on my 2000 Buick works. Turns out it's almost a 'free' measurement because there are already four wheel speed sensors as part of the antilock breaking systems so it only required additional software to develop the low tire pressure warning, no additional hardware needed.

I live in the land of roundabouts (you might call them traffic circles) so that wouldn't work for me since the tyres are never worn evenly.:slight_smile:

No, the Glow-Yo I was thinking of was a Yo-Yo with a centrifugal switch which made the thing light up when it was spinning fast enough.

Just kidding with the UV light yo-yo.. I've posted above an idea with the glo-yo switch and a pmosfet: when the centrifugal force pushes the switch on, it powers arduino, arduino as the first thing sets the gate to low, that will open the mosfet, and even the glo-yo switch gets released (ie while stopping the car) it will keep arduino powered. The arduino itself may decide then when it switches itself off (by setting the on/off control output high-impedance, default). Most probably an npn oc driver will be needed to control the gate.

Infineon solution;-

That is similar to NRF24LE1 chip, so atmega328p+NRF24L01+ would be the same setup basically.. :slight_smile: