Wanting to test home built lidar jammer

I am really suprised to see that there is not a larger hobbyist builders group for all sorts of jammers and upgrades to exsisting equipment.

I don't want people to violate warranties (some of this stuff is expensive ) but it seems to me the sheer number of things you could do to add onto and increase the effectiveness of gear you already have would be enough for our own mod group on these forums.

The guys at Blinder set a hell of a standard for jamming equipment. and believe me if I had the money in this economy I would have a blinder 27 in a heartbeat. But I think we could go down the road here with this and think about all the hacks and mods we could do lidar jammers and to radar/lidar detectors would be great to see

Some of the things I want to explore is "upgrade mods" to a cheap detector. Is it possible to get a cheap radar detector to perform closer to the 500.00 models? and do other things?. for myself I took and elcheapo and added an output to fire my lidar jammer. other mods could include adding IR photo transistors and sensors to the sensing circuit. Can you increase the sensitivity of the radar portion of your $50.00 detector. Can you actually make a Cobra sense Ka band (lol)

How about a simple trick of adding a lens and fiber optics from the grill to the lidar sensor on the detector?

In these tough economic times what about a "elcheapo" detector shootout, are there any hidden jems of units out there the perform supprisingly well? and can a simple tweak or mod make them better?

It would be nice to see more hobbyist out there. If anything for SCIENCE! and teaching purposes to help people understand why a cheap detector sucks vs a Bel STI driver. the actual teardown of the mysterious black box on your dash

Ahh if only I had more time :rolleyes:


My original intention for my jammer was to sweep frequencys high enough and with so much IR output that it would be seen as "noise" and not as an actual attempt to jam. Just enough randomness to confuse the sensor. if lets say it was trying to get a distance reading while the sun was setting.

Hopefully we will get to see soon the epic fail of this attempt, stay tuned!.

Solion

I think a big part of the problem for a hobbyist is you're experimenting with something that has the potential to get you a ticket if its done wrong, and its hard to test every situation, verses a company that has the resources and equipment to test against weaknesses in their system.

Looking at the pictures, I assume that you have the driving electronics on a separate board. (Pls. tell me if my assumption is wrong). If so, then the black wires connect an array of LED's to that board.

The main problem with using LED's to jamm LIDAR is creating short (VERY SHORT!) pulses. We're talking about nano second ranges here, to switch on (and off) a LED within a few ns , you simply cannot do that with wires that long.

This is a simplification, but suppose you want a single pulse to be 100ns long, then you're working in a 10MHz circuit. This is high frequency stuff where layout etc. becomes critical.

The receiver circuit of a lasergun filters on the very high frequencies that pulsed LASERS easily generate. The result of switching the LED's on to slow, is that (most) the signal is filtered out, you simply cannot get the IR power within the desired freq. spectrum, and the effective range (distance) of your jammer will be very short.

Switching LED's on/off that fast can be done in transistor based, switched, current source circuit. (LED + limiting resistor in emittor circuit) or by making the LED's part of a sort of resonating circuit. (Als Blinder does). Each solution requires very short connections, the right circuitboard and the right components. I personally found it a lot easier to use a pulsed laser diode.

If you solve this issue, you still have to solve the timing problems as discussed in this thread.

The jammer heads are indeed separate from the jammer board. I was not sure if that was really as serious as situation as the timings between detection and processing of the signal by the jammer and actual firing times for laser/leds on the professional units. I imagined it would be higher (talking ns here) In comparison to ultra simplified system like I have built.

So the question is this. from trigger pull on the lidar gun to active jamming how many ns is it for lets say a Blinder 27 to study and choose the proper countermeasure then fire the laser diodes/leds?

I will have my hands on a blinder unit here shortly and will fire up my scope and look at what it does and how it does it. I know that the sensors are built into the emitter heads , But is all processing done right there? does each head have its own processor? and what clock is it running at.

Again it should be fun . But I am very curious about the lidar guns. namely the nm range it accepts in Ir. Is it really filtered into a very very narrow frequency range for the sensor or is it a digital filter (probly both) People say that at about 2khz with enough output will brute force jam a gun. ( and probly throw a jam code)

But here is a thought experiment. lets say for the sake of argument that I go out and build an Ir array that drives 100 watts of Ir right in the sweetspot nm of the detector on the lidar gun. Now I know under normal circumstances that the gun is designed to look for its own pulses and throw out the noise. But can it actually see its own pulses through looking at the sun?

It would be like looking for the pulses of a flashlight while firing it into a searchlight at range. Its very caveman like way to jam but would it throw a jam code? (non pulsed light source ). If I am on the numbers with the frequency in Nm on my output , can I overload the detector as if they were looking at a car at sunset?..... hmmmm

DUDE WTF? How long have I been suggesting Open Source homebrew jammer idea and all of the sudden the Electronic geeks pop out of no where with 5 post counts! MUHAHAHHAHAHA 2010 bring it on!

I am really hoping something will start in the home brew crew. If anything to learn how to protect themselves better from getting nailed in this horrific economy.

Again I know people say that there are no good laser/radar detectors for under 100.00 . but are there any bright spots in that? can a simple mod make a cheap detector better?

There are alot of really neat things I think can be done to existing hardware. I hope we can goad people into getting curious about hacking and improving on designs.

solion

What about a USB phigets device as the interface, and use something like Windows mobile as the platform, since it would open this up to many more people? I'd be willing to do some coding on something like that.

I can't remember the exact wattage, but it has been asked before how bright something has to be to where the gun can't find it's own pulse. All I remember the Prof. saying was that it wouldn't be eye safe.

I can imagine that if we were talking about lasers and coherent light, then yes I would agree. But what about a diffused effect over lets say a 30deg angle. I may try this with an array of 5w Ir leds at some time to see if there is any effect.

However, here is a thought. Diffusion of Ir through the polycarbonate lenses of the headlights/marker lamps. Now I know that this would not work for every vehicle but at least with my car my only real source of reflectivity is through these sources. ( dark car no front lic plate, all other reflective sources blacked out ) If we were to diffuse a large ammount of IR through this medium would it work for some cars....

Interesting 2010 to be sure

lastly , could someone confirm that Lidar guns actually use a 25w laser in them?!

solion

Quote:

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Originally Posted by Solion

lastly , could someone confirm that Lidar guns actually use a 25w laser in them?!

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Prolaser patent:
"The gallium-arsenide laser produces laser energy having a wave length of 905 nanometers with a peak power output of approximately 50 watts and a 30 to 50 nanosecond pulse width."

Laser Atlanta patent:
"In a preferred embodiment, the emitter is a GaAs type, producing laser radiation having a wavelength of about 905 nanometers, with a peak power output of approximately 50 watts and a 30-50 nanosecond pulse width. "

Quote:

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Originally Posted by ELVATO

I can't remember the exact wattage, but it has been asked before how bright something has to be to where the gun can't find it's own pulse. All I remember the Prof. saying was that it wouldn't be eye safe.

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Yeah so even with the reflection being weaker, if you wanted a CW source to be "so bright that the gun couldn't find it's own pulse", you would probably need a CW source of several watts. Certainly not practical, definitely not eye safe, and you would need a BIG power supply.