-------------------------Monitor------------------------ The Newsletter for PC-Based Data Acquisition and Control Issue 107 www.windmill.co.uk June 2007 --------------------ISSN 1472-0221---------------------- Thank you for subscribing to Monitor. In this issue we discuss how to continually log and display your vehicle's emissions, location, speed, fuel consumption and other values on your PC. By interfacing your laptop to the vehicle's on-board diagnostic system you can show live data, store it to disk, replay it later and map it. I hope you enjoy the newsletter but should you wish to cancel your subscription you can do so at https://www.windmill.co.uk/newsletter.html CONTENTS ======== * Windmill News: Displaying Real-Time Fuel Consumption * Logging data from a vehicle to a PC * Excel Corner * DAQ News Roundup ________________________________________________________ ________________________________________________________ Windmill News: Displaying Real-Time Fuel Consumption ________________________________________________________ Robert Kwiatkowski wanted to see his fuel consumption whilst driving. He therefore connected a laptop to his Ford truck and used Windmill software to collect data from the on-board diagnostics system. In most countries, new vehicles have to have an on- board diagnostics system. This monitors conditions and components that are related to vehicle emissions. Kwiatkowski used Windmill to collect Mass Air Flow and Vehicle Speed readings. He set Windmill to automatically send the data to Excel where the fuel consumption was calculated. Modern vehicles use data from oxygen sensors to control the air to fuel ratio. This ratio is set at the chemically ideal value of 14.7 grams of air to every gram of gasoline. The Mass Air Flow is the mass of air consumed in grams per second. Kwiatkowski used this information to convert the Mass Air Flow to gallons per hour and then calculate miles per gallon. He set Windmill to route the readings to Excel which performed the necessary calculations and showed the current fuel-consumption. Although the system is designed to show real-time fuel consumption, all the data can be logged and reviewed later. Windmill can also record GPS co-ordinates alongside the vehicle data. Other data could be recorded, such as emissions. This means that the system could be adapted to show emission maps of journeys through specific areas. Further Reading =============== Robert Kwiatkowski has produced a step-by-step guide to replicating his system which he has kindly made available at https://www.windmill.co.uk/obdii.pdf For an overview of using Windmill with OBD systems see https://www.windmill.co.uk/obd.html ________________________________________________________ ________________________________________________________ Logging Data from a Vehicle to a PC ________________________________________________________ All modern cars have an on-board diagnostics system. This is known as OBD-II, EOBD or JOBD depending on whether the car uses the American, European or Japanese system. All these systems work in a similar manner. In today's engines sensors monitor the operation of specific components whilst actuators maintain optimal engine control. An on-board computer, sometimes known as a "powertrain control module" (PCM) or an "engine control module" (ECM), controls these systems. The sensors and actuators, along with the diagnostic software in the on-board computer, make up the OBD system. The on-board diagnostics make their data available to you through a 16-pin port. The OBD is primarily an emissions control system. However, as you can access all the sensor readings you can use it for many applications. Our opening story told of how it could be used to display fuel-consumption in real-time on a PC. There may be as many as 300 readings available from your vehicle: including engine rpm, vehicle speed, emitted oxygen, intake air temperature and ignition timing. Add a GPS receiver and you could log the location of each reading. * How to Get the OBD Data into your Laptop ======================================== 1. You need an interface to connect the vehicle's on-board computer to your laptop. Although the on-board diagnostics are standard across cars, the interface isn't. You need to buy one that matches your vehicle. Connect the interface between the vehicle's 16-pin diagnostic port and one of the laptop's ports. 2. You need some software, like Windmill, to request data from the OBD, read the response and log, display and distribute the data. The free Windmill 4.3 software reads ASCII data from the PC's COM port. So if you plan to use Windmill make sure your interface can be plugged into the COM (RS232) port and transmit ASCII data. With Windmill you can read any of the OBD information: the standard stuff and any extras provided by your vehicle manufacturer. 3. You will need to perform some calculations on the data so a spreadsheet like Excel would be useful. * The Structure of the OBD Data ============================= To obtain data send a request then wait for a response. Commands to Request Data... ------------------------------- A command to request data is usually two or three bytes long, but the OBD standard allows for up to seven. The requests are sent in hexadecimal. The first byte sent is the Mode byte. There are nine modes of operation in the OBD standard. For regularly logging data you will generally use Mode 1: Show Current Data. So start all your requests for data with "01". The next byte describes the information wanted. You specify this with a "PID" code. PID stands for parameter identification number and is a hexadecimal number. Here are some of the PIDs you might use. For a full table download https://www.windmill.co.uk/obdii.pdf and see Appendix C. PID Description (Number of bytes returned) 05 Engine Coolant Temperature (1 byte) 0A Fuel Pressure (1 byte) 0B Intake Manifold Pressure (1 byte) 0C Engine RPM (2 bytes) 0D Vehicle speed (1 byte) 0F Intake air temperature (1 byte) 10 MAF air flow rate (2 bytes) 1F Run time since engine start (2 bytes) 2F Fuel Level Input (1 byte) 31 Distance traveled since codes cleared (2 bytes) 33 Barometric pressure (1 byte) 46 Ambient air temperature (1 byte) To request a vehicle speed reading, therefore, you would send 010D. Finally you may need to tell your interface that you have finished the request message. The character to do this depends on your interface: in ELM interfaces it is a carriage return. Some interfaces require you to send a fixed number of bytes so no ending character is required. Once configured Windmill Software regularly sends this command to the OBD interface and stores the reading received. How to Interpret the Data Received... ----------------------------------------- In our above speed reading, the message returned would be in this format: 41 0D 37 41 - shows a response (4) from a Mode 1 request 0D - the PID of the measurement, speed in our case 37 - the data value in hexadecimal With Windmill we would extract the data value from the rest of the message. So we might tell it to ignore six characters then extract two. For speed just one hexadecimal number is returned. Other types of data may return 2 or 3 hexadecimal numbers (bytes). See the table above for details. We now need to convert the hexadecimal value to decimal. If using Windmill we could send the data to Excel (or another analysis program) and perform the conversion there using the HEX2DEC command. Finally, you may need to apply a scale and an offet to the results. You can get the Windmill software to do this before it presents the results, or you could do so after data collection in Excel. * Further Reading =============== A guide to configuring Windmill for OBD systems https://www.windmill.co.uk/obd.html Getting Data from Windmill into Excel https://www.windmill.co.uk/excel/ ________________________________________________________ ________________________________________________________ Excel Corner ________________________________________________________ We've updated our Excel pages on the Windmill web site to reference all the tips and tricks we have been giving you in these newsletters over the last 6 years. For tips on using Excel charts see https://www.windmill.co.uk/excel/excel-charting.html and for help using Excel for data acquisition and analysis see https://www.windmill.co.uk/excel/ If you have a question about using Excel for data acquisition then fill our form at https://www.windmill.co.uk/excel/ ________________________________________________________ ________________________________________________________ DAQ News Roundup ________________________________________________________ Welcome to our roundup of the data acquisition and control news. If you would like to receive more timely DAQ news updates then grab our RSS newsfeed at https://www.windmillsoft.com/monitor.xml. Read https://www.windmill.co.uk/newsfeed.php for notes on how to display the news on your own web site, read it via e-mail, mobile phone or a newsfeed viewer. First Buoy to Monitor Ocean Acidification Launched The first buoy to monitor ocean acidification has been launched in the Gulf of Alaska. Attached to the buoy are sensors to measure climate indicators. These transmit their readings via satellite. The instruments will measure the air-sea exchange of carbon dioxide, oxygen and nitrogen gas in addition to the pH. The buoy is anchored in water nearly 5,000 meters deep. Source: National Science Foundation http://www.nsf.gov/news/news_summ.jsp?cntn_id=109619 Thirsty Crops to Signal Farmers Corn and potato crops may soon provide information to farmers about when they need water and how much should be delivered, thanks to a University of Colorado invention. The technology includes a tiny sensor that can be clipped to plant leaves charting their thickness, a key measure of water deficiency and accompanying stress. Data from the leaves could be sent wirelessly over the Internet to computers linked to irrigation equipment, ensuring timely watering and cutting down on excessive water and energy use. Source: University of Colarado at Boulder http://www.colorado.edu/news/releases/2007/244.html New Quality Measurement Data Standard National Institute of Standards and Technology (NIST) researchers have completed work on a new data specification that will allow compliant products to store and exchange measurement data from process- monitoring instruments in a completely open and non- proprietary format. Widespread use of the new quality measurement data (QMD) specification, which defines the information exchanged between factory floor measurement instruments and Statistical Process Control (SPC) software, should provide substantial savings to quality systems users and their suppliers throughout the manufacturing sector. Source: NIST http://www.isd.mel.nist.gov/ Research Tower Could Aid Tracking Of Contaminant Plumes America's first network of research instruments to predict urban movements of toxic or radioactive contaminants is being completed in Washington DC. Using data from the new network, scientists expect to create and test computer models that would calculate a contaminant plume's spread. The new monitoring station will include a device called a sonic anemometer that uses high-frequency sound waves to measure wind velocity in all directions simultaneously at brief time intervals. With such data, scientists can analyze local air turbulence that strongly influences where and at what rate airborne contaminants spread in an urban environment. Source: AGU http://www.agu.org/ Steady Growth in Worldwide PLCs Market IMS Research forecasts that the worldwide market for PLCs will grow steadily to surpass $9 billion by 2011, growing at around 5.0% per year. The Asia Pacific region is forecast to experience the strongest growth, with an estimated compound annual growth rate of 7.9%. Source: IMS https://technology.ihs.com/members/pr.asp?X=372 ________________________________________________________ ________________________________________________________ * Copyright Windmill Software Ltd * Reprinting permitted with this notice included * For more articles see https://www.windmill.co.uk We are happy for you to copy and distribute this newsletter, and use extracts from it on your own web site or publication, providing the above notice is included and a link back to our website is in place. An archive of previous issues is at https://www.windmill.co.uk/newsletter.html and an index of articles at https://www.windmill.co.uk/newsletter.html Windmill Software Ltd, PO Box 58, North District Office, Manchester, M8 8QR, UK Telephone: +44 (0)161 833 2782 Facsimile: +44 (0)161 833 2190 E-mail: [email protected] https://www.windmill.co.uk/ https://www.windmillsoft.com/ Do you have a question, comment or suggestion on this newsletter? Fill in this form to contact the editor.
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June 2007
