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On-Screen Digital Distance Meter

Discussion in 'General Electronics Discussion' started by Last_Mavrik, Feb 14, 2013.

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  1. Last_Mavrik


    Nov 15, 2012
    Hello again everyone!

    I have a much more in-depth project that I can't seem to find an existing product for. Here's the issue:

    Short Version:
    -I need to find a distance measurement device to display the length of cable passed through/by it on an LCD screen that already has video being passed through said cable.

    Long Version:
    -If you do a Google Search for "On Screen Footage Counter", you will find immediately, several listings for Sewer Camera systems that feature an on-screen display of the distance their cable has reeled out, thus being able to be recorded on a DVR system and shown to the customer.

    -The company I work for is nearly to the production phase of our first in-house designed Sewer Camera, and while we've managed to overcome every other engineering hurdle, save this one. To my knowledge, having searched for hours online, the only available cable measurement devices are digital or LCD display on their own small counters; nothing that can easily be wired into an existing video feed and displayed on an LCD Monitor.

    -Being a repair technician, I've seen several methods in other sewer cameras (Wheels that ride the cable reel, wheels that run along the cable through a housing, even a jury-riged device using an electric guitar optical encoder as a turn-wheel), but none of the devices have an consumer counterpart that could be incorporated into any other application. All are designed by/for the camera they're used on.

    -So, I find myself here looking for any ideas/input from the electrical community. I may not be heavily versed in circuit board creation or programing, but if anyone knows of a way to take a simple device for distance measurement and add it's output to a standard analog video signal over an RCA cable to an LCD Monitor, we should be able to handle the rest.
  2. CocaCola


    Apr 7, 2012
    You want a video overlay circuit, not all that complicated there are even dedicated chips that will do it for you... IMO you would be better off using a micro to not only calculated the distance but to also do the overlay to reduce parts count in the design... There are many examples out there if you Google up video overlay circuits...

    As for the mechanics of a simple pinch wheel measuring device, it's not all that complicated to design if absolute precision isn't needed... A wheel with a diameter of say 5 inches with 5 equally spaced holes and an optical sensor will give you 1" resolution and is dead simple to have the micro count and measure, you just need to let the micro know of forward or backward direction though...
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