Practical Arduino Cool Projects for Open Source Hardware- P35: A schematic or circuit diagram is a diagram that describes the interconnections in an electrical or electronic device. In the projects presented in Practical Arduino, we’ve taken the approach of providing both a photograph and/or line drawing of the completed device along with a schematic. While learning to read schematics takes a modest investment of your time, it will prove useful time and time again as you develop your projects. With that in mind, we present a quick how-to in this section | CHAPTER 15 VEHICLE TELEMETRY PLATFORM c2 Direction of longitude E East W West a . dl Position type 0 Invalid or not available 1 Autonomous position 2 RTCM or SBAS differentially corrected n . d2 Number of satellites used in position computation nn . fl Horizontal dilution position HDOP . f2 Altitude in meters above the reference ellipsoid. For 2-D position computation this item contains the user-entered altitude used to compute the position computation. M Altitude units M meters a . f3 Geoidal separation in meters . M Geoidal separation units M meters a . d3 Age of differential corrections in seconds nnn . d4 Base station ID for RTCM use only nnnn . cc Checksum. Most developers think of NMEA 0183 only as a way to talk to GPS receivers but it s actually a much more general communications protocol that is used in marine environments for a whole range of devices including echo sounders autopilots and weather sensors. Wikipedia has more information about the NMEA 0183 standard at wiki NMEA_0183. Assemble the Power Supply on the Shield Normally the power supply circuit is the most boring part of a project but this one has a few tricks that are worth paying close attention to. See the schematic in Figure 15-17. 319 CHAPTER 15 VEHICLE TELEMETRY PLATFORM Figure 15-17. Schematic of Vehicle Telemetry Platform power supply Because this system will run directly from the car s power we need to regulate it down from the 1214V range provided through the OBD-II connection to a nice consistent 5V. However keep in mind for other automotive projects that although the vast majority of cars operate on a 12V negative-ground system there are exceptions many trucks operate at 24V motorcycles at 6V and some modern cars use an internal 42V power bus. Because we re using the OBD-II connector as the power source and the OBD-II standard stipulates that it supply 12V we re fairly safe. But if you try connecting directly to a vehicle power supply there may be .
