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  1. #1

    Lightbulb Anyone tried DIY laser jammer?

    So I know that many of the current technology laser jammers use sophisticated DSP and other processing techniques to detect incoming laser signals and effectively jam them, all of which is probably way to advanced for even a skilled hobbiest.

    However after reading several posts about the brute force method of laser jamming it seems much more doable. From what I have read, and correct me if I am wrong, it is possible to jam a laser gun if you send out IR pulses at a high enough frequency. Obviously for this to be effective with no detection circuitry, this sort of jammer would have to be always running.

    I am wondering if anyone has ever tried this or could direct me to more information about this method of jamming? It seems like this could be quite dooable for anyone familiar with circuit design and electronics.

    basically my idea at the moment is to construct a bank of IR LEDs and a high frequency drive circuit which constantly pulses them at say, 4 MHz or so. I know at high speeds and powers you can risk burning up the LED's but I figure with a large enough bank you could alternate which LED's are on and effectively lower their pulse rate. Another thing I am curious about is at what duty cycle is it best to pulse the LEDs. I am guessing something below 50%. But lower would improve upon the LEDs power handling.

    This seems like a cool project which if given enough thought could actually work. If anyone could point me in the right direction or give me any additional information on this topic I would greatly appreciate it. If it does seem feasible I would gladly share the details of my design we everyone on here.



  2. #2
    Advanced Member
    Join Date
    Feb 2005
    Southern MA

    Default Re: Anyone tried DIY laser jammer?

    Won't work!!!! Mythbusters tested this with a bunch of IR LEDs and it failed to jam the laser gun.

    There is more to laser jammer than just IR light

    Spoiler: show

    Radar Detectors-V1 & BEL v995
    Laser Jammer-Laser Interceptor Quad
    GPS Camera Locator-Cheetah C100
    GPS Nav-Garmin nuvi w/Trapster
    CB Radio-Galaxy DX-949 w/Wilson 500
    Scanner-RS Pro-96

  3. #3
    Old Timer
    Join Date
    Nov 2006
    Cleveland/Shaker Heights, Ohio, USA

    Default Re: Anyone tried DIY laser jammer?

    ^ I think that what charliepuch proposed above is different, though.

    I think he's trying for a brute-force jamming method, akin to the LE-10.

  4. #4

    Default Re: Anyone tried DIY laser jammer?

    Yes Exactly, the brute force method.

    My circuit skills are a little rusty, but as of now I'm thinking of using a pierce oscillator circuit to generate the pulse cycle, and then up the output current with some high speed opamps and then send that signal to a bank of high speed IR LED's.

    Right now I'm looking at some that Vishay make. The specs are as follows:

    peak wavelength: 890 nm (close enough to 904 nm)
    rise time: 30 ns (gives a maximum frequency of 16.6 MHz (1/(2*rise time)))
    Radiant intensity: 180 or 70 mW/sr (180 for 10 degree half power angle and 70 for 22 degree half power angle)

    These LED's have the highest output and rise time for a wavelength that is close to 904 nm.

    Which brings up another question. Do all police laser guns operate on the 904 nm wavelength?

  5. #5
    Join Date
    Aug 2008
    SW FL

    Default Re: Anyone tried DIY laser jammer?

    Read this...

    Your method sound feasible if you can get the response time and output from the LEDs....You will need a lot of LED considering the 890 vs 904nm. Also you will be throwing jam codes.

    I don't think its necessary for the LEDs to be on all the time. You will need a detect circuit that then fires the LEDs when it detects a laser hit.

  6. #6

    Default Re: Anyone tried DIY laser jammer?

    As far as detection circuitry goes I don't plan on having any, as that adds considerable complexity to the project. It seems safer to just have it on all the time. I feel like I could rely on my radar detector and eyes to pickup that I'm being lasered, and just have this device to buy me some time so that I can slow down.

    yes I would have to use extra LED's but they are all really cheap the ones I'm looking at with the 22 degree half power angle are 34 cents each, so not bad.

    if anyone is interested the LED is made by Vishay, and the part number is: tshf5410. I would post the link to the datashet but I don't have 15 posts.

    Based on the data sheet it looks like the relative radiant intensity at 904 nm is about 0.7. so basically I would have to use about 1.4 times as many LED's as I would if they were designed to run at 904 nm which really isn't too bad.

    If I flashed the LED's at a rate of 4 MHz that gives a period time of 250 ns between subsequent flashes. The rise time of the LED's are 30 ns and lets say I apply power to them for an extra 20 ns. That means that the LED's are receiving power for 50 ns per cycle which translates to a 20% duty cycle. Again referring to the data sheet I can see that with this duty cycle and pulse duration I can operate the LED's with a maximum forward current of 400 mA each! That's four times more power than they are rated in continuous operation which is only 100 mA each. To be on the safe side and to increase the reliability I would probably operate them at 200-300 mA. It seems like these LED's might be a good choice for this application.

    As far as jam codes go I don't live in a state where using a laser jammer is illegal, nor do I drive through any of those states, so I seem to be okay there. Besides the officer knowing you are jamming him, are there other downsides to throwing jam codes?

    So not that it seems like I got the LED's picked out now its time to determine how many I need, and work out the control circuit Does anyone have any idea or rough estimate of about how much power I should go for? Also, how about the half power angle for the LED's I'm thinking I want to go with the 22 degree instead of the 10 degree even though I will have to use more LED's, it gives a wider area of illumination which I feel is better since the cop is always a little off to the side when he clocks your speed.

    Anyways thanks again for all the help!


  7. #7
    Join Date
    Aug 2008
    SW FL

    Default Re: Anyone tried DIY laser jammer?

    I'm not sure the dector circuitry would be that hard. You could couple the alert ouput on your radar detector.

    Also, if you are running the LEDs continually, you may need to deal with thermal issues. High junction temps kills LEDs, so running them hard and continually will lead to reliability or output degradation over time. So my point is that you probably want a detection circuit so you don't have to continually fire your LEDs.

    I'm not sure on total output intensity you need, but maybe if you study the Blinder models you can get an idea of the required output.

    Also, it maybe worth a look at Roithner. They produce LEDs (and laser diodes). They have some high ouput LEDs at 905nm...They are likely more expensive.

    Good luck with the project and keep us posted.

  8. #8
    Join Date
    Aug 2008
    SW FL

    Default Re: Anyone tried DIY laser jammer?

    look here....scroll to the bottom to see high speed ir LED stuff

    Pulse Circuits for Infrared LEDs and Visible Diode Lasers

    just in case you can't see the link...

  9. #9

    Default Re: Anyone tried DIY laser jammer?

    Thanks for all the help so far!

    I checked out the High output LED's from Roithner, they look pretty good as far as wave length and intensity go, but the data sheets are kind of lacking, in that they don't specify rise and fall times as well as safe operating ranges. My guess is that they are designed for continuous operation and are not high speed or designed to be pulsed.

    The problem with the detection circuitry is that, while you can connect an IR photo receptor to the whole device, interpreting what is sees is much more difficult, almost an art form. I'm guessing that if I go the analog route this would involve a lot of filters to filter out unwanted light frequencies and non pulsed light as well as many other factors that don't come to mind at the moment. My best design would most likely work very poorly in that it would trigger tons of false alarms, or worse, not work at all. One way I can overcome this is to design the pulsed LED system to be very robust so that it can be continuously run without thermal issues. That way I never have to worry about whether my makeshift detector is actually going to trigger the device correctly.

    As far as the thermal issues you described, I feel that if i design the led's to be run at a safe margin below and within the safe operating area specified on the manufactures data sheet then I should not have to worry about over driving the LED's and the thermal issues that can cause.

    Last night I designed an oscillator circuit that makes use of a high speed opamp to generate a square wave at a specified duty cycle. Next I will design the high power driver circuit which will use this oscillator as the trigger signal for the LED pulse.

    I will be sure to upload pictures and schematics as soon as I hit the 15 post mark, as the forum will not allow me to do so until then.

    As always, thanks for the help!

    Any and all feedback/suggestions/comments are always appreciated,


  10. #10
    Radar Fanatic
    Join Date
    Dec 2007

    Default Re: Anyone tried DIY laser jammer?

    I say make one and get a PLII and see if you can jam it. If it works for a little while then great, if not you'll at least have gained lots of knowledge on what goes into a lidar gun's readings and what it takes to prevent that, which will make you smarter and more skilled in your tactics down the road in this cat-mouse-rabbit game that we play.



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