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Thread: Dashcam video with GPS speed imprint - court date soon...

  1. #71
    Variable Bitrate
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    thanks, that is really slick.

  2. #72
    Raw Wave tj!2k4's Avatar
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    Exclamation Group Buy Policy

    Quote Originally Posted by [H]Bugster View Post
    Is anyone interested in a group buy of the SD DVR device? i found a seller who is willing to sell it for less than $150 +shipping if we can get more than 10 people interested. This goes for $200-$250 elsewhere normally
    Group Buy Policy

    This is too good of a thread to see locked or deleted.

  3. #73
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    Aug 2003
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    Got GPS overley device today. It's just a board with the components on it - you have to mount it and solder your own wires etc on it.

    The connections are:

    1) Rx and Gnd from the DE9 serial port that connects to the serial device. Must be NMEA coming in at 4800 8-N-1

    2) Power 12v

    3) Video in and video out


    The GPS overlay board cost ~$130 after shipping and the Garmin GPS18PC adds another ~$70. The project box and other mounting stuff came to ~$20. Overall about $220 and maybe 3 hours of total work to find, order, build install and test the finished GPS overlay box.

    The intructions for soldering are very simple and the PCB is well marked and professionally made. Took about 5 mins to solder it all together - another 30 mins to mount connections in the project box that would allow the unit to be removed easily form the car - nothing hardwired. Plus add 15 minutes to quadruple-check polarities and ensure the video signals were's shorted. (Letting the smoke out of a DVR is a mistake you only make once.)

    I hooked it up to my ancient handheld Garmin eMap GPS device and it worked like a charm - Location, Heading, Speed and time (UTC/GMT/ZULU). I didn't see where I could change the timezome, but that's not a problem because the DVR already has a timestamp, the 4 or 5 hour offset is easy to explain and I'd probably wind up having the switch the time with daylight savings anyway.

    The DVR setup is becoming more complex now with a few external project enclosures that I didn't have initially. GPS overlay, Dual 5a 12V power regulator to provide clean power, a multiple isolated trigger module (so the DVR can be triggered by opening the door or via a vibration sensor), power on-off timer (keeps the DVR on for at least 30 seconds per run so that there's no suddent dropout during start etc.) and the tank battery (to survive the crank). I'm going to have to change the DVR mount to allow space to arrange all these extra boxes. :-/









    I'll post a picture of the gps data overlaid when I can get a change to get out a drive the car and get some real numbers on the screen.

    One problem: If the GPS overlay board loses power or has some problem then the video signal it is passing through is cut off. Because of this I'm going to loop a copy of the front camera from ch1 back into ch4 and add the overlay to ch4. In the event of a loss of video due to the GPS board I want to make sure the dashboard-mounted front camera is preserved. It also allows me the option of exporting the front camera in fullscreen with or without the speed reading depending on if I want people to know how fast I was going. ;-) ch will have the front camera, and ch4 will have the front camera with the GPS data burned into the recording, so the evidence is going to be admissable.

  4. #74
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    GPS Overlay demo:

    [media]http://www.youtube.com/watch?v=UCZZh0ykFmk[/media]


  5. #75
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    Followup: The speed displayed by the GPS overlay device is whatever the GPS antenna sends it in the $GPRMC sentence - which is KNOTS not MPH. The conversion is easy enough though when you're playing the video back. I'm going to look at building a converter daughterboard based on a Zilog Z8 processor that will take and parse the GPRMC sentence and replace the speed with MPH.

  6. #76
    Newbie TripleThreat's Avatar
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    GPS Strings

    Can't you just have the GPS output the Nema info in MPH instead of Knots. I can change that in my Garmin setup. Newbee so don't kill me to bad...What are the white blocks from?

  7. #77
    Confusion Master
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    Quote Originally Posted by TripleThreat View Post
    ...What are the white blocks from?

    He's blocked out his location and something else.

  8. #78
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    The white blocks are covering up my location and my name. I'm paranoid that way, sorry. :-)


    My research showed that I was unable to configure the GPS device to output MPH in the $GPRMC sentence. Instead I am building a Zilog Z8 MCU based circuit that will intercept and modify the sentence. It makes 3 key changes:

    1) Speed is in MPH, and labelled as such.
    2) Heading is changed to direction such a N instead of 0 or NE instead of 45.
    3) Time is adjusted to a timezone based upon an offset configured using a row of dip switches to specify offset in hours. The first bit will be 0 for adding and 1 for subtract, and the rest of the bits will be a number between 1 and 23 to specify the hours offset from UTC. so 1000 0100 = -4 hour offset. 0000 0001 would be +1 hour.


    I have the circuit working on the zilog dev board and I'm gonna spend a day this week etching a PCB. Then I can install the circuit within the same project box as the existing GPS overlay.

  9. #79
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    Man, I am so glad to see others doing this. Can you imagine if just 20% of all cars had this type of technology? I think it would cause a significant increase in law enforcement honesty. Those that don't have it would benefit from those that do.

    Scruit, I wish I had just a fraction of your knowledge of electronics.

    For those interested, I have a video overlay box with video in/out (RCA) 9-12V input and serial input with cable to DB9, and a hand held Garmin GPS receiver (with separate power/data cable) that I no longer need. I upgraded my car with the all-in-one box from the English firm - so now both cars have exactly the same setup. I have no need for the separate GPS and overlay box. PM me if anyone is interested.

  10. #80
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    Quote Originally Posted by erkme73 View Post
    Man, I am so glad to see others doing this. Can you imagine if just 20% of all cars had this type of technology? I think it would cause a significant increase in law enforcement honesty. Those that don't have it would benefit from those that do.

    Scruit, I wish I had just a fraction of your knowledge of electronics.

    For those interested, I have a video overlay box with video in/out (RCA) 9-12V input and serial input with cable to DB9, and a hand held Garmin GPS receiver (with separate power/data cable) that I no longer need. I upgraded my car with the all-in-one box from the English firm - so now both cars have exactly the same setup. I have no need for the separate GPS and overlay box. PM me if anyone is interested.

    I had some fun this morning:

    [media]http://www.youtube.com/watch?v=ITHQjfSbEKo[/media]


    THe GPS overlay is not in place because I'm still working on the MP conversion circuit.

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