Connect with us

Speed trap DIY

Discussion in 'Electronic Design' started by Old Man, Aug 18, 2004.

Scroll to continue with content
  1. PaPaPeng

    PaPaPeng Guest

    Have the slipstream do the work of triggering a warning light.

    Have some sort of spring loaded vane where the slipstream of a
    speeding car can cause the vane to swing and close a switch. That
    switch triggers a flashing LED some distance ahead of the driver, say
    10 to 20 car lengths. The LED is straight ahead and far enough for him
    to keep his eyes on the road so as not to cause an accident. Yet the
    LED will cause him to do a double take as to whether that was a radar
    trap or a camera's light. With luck he might just slow down.
  2. Paul Burke

    Paul Burke Guest

    Someone near here nailed a crude sign saying "Speed Trap Ahead" to a
    tree at the side of the road. Very effective. But now all the Jags and
    BMWs have speed trap detectors, a little transmitter of appropriate
    frequency ought to work too.

    Paul Burke
  3. Fred Bloggs

    Fred Bloggs Guest

    Okay- it looks like this technique has been worked out but it does not
    use Doppler. A very promising technique uses two inexpensive
    omni-directional microphones, treats the sound signal as a complete
    unknown, and directly estimates speed using the maximum likelihood
    principle, reduces to computing the speed that maximizes the correlation
    between the microphone signal sample records with relative time shift a
    function of the hypothetical speed parameter, and this sample record
    encompasses received signals before and after the closest point of
    approach to both microphones. The microphone spacing can be as small as
    1 meter and the processing has been reduced to ordinary DSP practice.
    Although theoretically complex, the actual implementation is simple.

    As usual the brain-dead OP has evaporated with a GEE-WHIZ THNX! reply to
    the worst suggestion- but this is posted anyway.
  4. Old Man

    Old Man Guest

    Well - I am not brain dead yet... I have been reading with enthusiasm the
    posts. I like the zero cost versions (sign with speed trap ahead... Full
    size cut out...)

    On another road is a practical example of a no cost speed reducer - a
    local sheriff drives his home and parks it at the end of his driveway. I
    know its there, I see it everyday, and I still check the speed as I go
    by, very effective. Now all I have to do is talk him into loaning me the
    car over night for the end of my driveway... ;-) hehehehe.

    I live in Pennsylvania, USA, and it is illegal for the cities to have
    radar guns. Only the state cops are allowed. What they do is paint a
    couple white lines on the road, then sit there with some kind of timer, I
    figure that I could invest in a can of paint and borrow an accurate
    measuring wheel, and then a little code on the PDA, should be simple.
    Once I get the code working, maybe a couple photocells, and a toy
    telescopes, when the car goes over the line the light value might just
    shift enough to trigger something. Plus it keeps everything on my side
    of the road, and I don't have to involve the neighbor.... Plus the white
    lines will definitely give motorists a pause...

    I told the wife of my plans to build the kit - after she stopped
    laughing; she convinced me that that money could be better used in other
    venues... Can't argue with authority...
  5. Jim Thompson

    Jim Thompson Guest


    I don't know whether they still do it or not, but Oklahoma used to
    paint wrecked cars in police colors and leave them by the side of the
    turnpike... caused many a panic braking ;-)

    ...Jim Thompson
  6. A motion detector tied to a muted strobe light might be enough. Best if
    it flashes the vehicle from behind, when they have passed it already. Let
    them draw their own conclusions.


    Sir Charles W. Shults III, K. B. B.
    Xenotech Research
  7. Active8

    Active8 Guest

    On Fri, 20 Aug 2004 16:00:30 GMT, Old Man wrote:

    Oh. So *that's* why this shithole has so much LIDAR. I'm definitely
    getting a LIDAR detector now.
    I'll be the one shooting holes in your sign as I fly by at breakneck
    speed. I use the legit ones to check the calibration of my
    Let me know when she dumps you. I like her already ;)
  8. David Harmon

    David Harmon Guest

    On Wed, 18 Aug 2004 15:11:05 GMT in, Spehro
    I heard a call on the scanner a while ago... the police had set up one
    of those and the local drag racers were using it to gauge their
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day