Ultimate unbeatable jammer, crazy idea?

[JDS]

Maybe alcohol and sleep deprivation are clouding my judgement, buy I just had an idea...

Let's say, theoretically, that you don't care about throwing jam codes on LIDAR guns, you don't care about throwing jam codes WHILE jamming to gun, and you don't care about pissing off assholes who use the laser cruise control in their Infiniti FXs. In other words, you're me.

Now let's say you bought a ****load of infrared LEDs and mounted them to the front and rear of your car, wired them to a simple circuit board to fire them at 4 MHz whenever power is applied, and wired that board to your fuse box through a switch in your dash.

Now, any time you're driving the car, whenever you want to become immune to LIDAR (which may be from the moment you start the car to the moment you park, if you so choose), you are.

Is this possible? Is there some reason why the LEDs couldn't be mounted with enough cooling to sustain constant operation? Are there any problems I have not foreseen?

[ivirovets]

I can't really say much because I'm not sure how jammers actually jam, but I don't think LEDs can pulse at that high of a frequency. Laser diodes might be more suited, but those are expensive as sh!t in mass quantities and do heat up considerably. Any jammer/LED experts care to chime in? Otherwise seems like a possibility

[Laser-InterceptorUSA]

I can't really say much because I'm not sure how jammers actually jam, but I don't think LEDs can pulse at that high of a frequency. Laser diodes might be more suited

You would be correct! LED's have much slower rise/fall times than laser diodes, so they cannot be operated at the high frequencies necessary and still produce pulses.

Cliff

[OpenRoad]

I like the idea. A C/O jammer. Perhaps (if budget is not a problem) a series of heads, where a set goes off for an interval, shuts off, and the next bank kicks in, allowing others to cool down before being brought back online.

Would be ugly as sh_t on your car though.

[JDS]

I can't really say much because I'm not sure how jammers actually jam, but I don't think LEDs can pulse at that high of a frequency. Laser diodes might be more suited

You would be correct! LED's have much slower rise/fall times than laser diodes, so they cannot be operated at the high frequencies necessary and still produce pulses.

Cliff

Crap.

So are LED jammers, using "smart" jamming, operating at lower pulse rates than "brute force" jamming requires?

I wonder, would it be possible to use the circuitry to "synchronize" the LEDs to pulse out of phase with each other, therefore creating a higher effective pulse rate? That is, every time you double the number of LEDs, you double the effective pulse rate? Or is the pulse rate of LEDs multiple orders of magnitude slower? Or for that matter, would the synchronization be impossible?

Would be ugly as sh_t on your car though.

Not with LEDs, they would look a lot like those LED running lights, except they wouldn't be lit up.

[TurbineDivinity]

I was reading this on another site, If he is right this would be simple to build with leds.

Moderator Edit: You may not present the work of others here without permission from the source and a link.

[fulcrum]

In theory this can be done. LED's are usable in jammers. (example: Blinder). But the practical realization is not going to be as simple as you might think.

To use a LED as a pulsed IR source that can be "seen" by a jammer, you have to switch it on (and off) very fast. A practical electronic circuit to do that can probably just drive 1 or 2 LED's. If you want to drive the LED's at 2-4 MHz you cannot drive the LEDs at a very high current otherwise they will overheat and destroy. Blinder drives its LEDs at a few Amps of current but at a low frequency, so they won't overheat. (just) If you run them at 2-4 MHz you might be able to drive them at 0.1 to 0.15? A. The (pulse) energy output of each LED will be a lot lower then the output in the Blinder. My best guess is you will need around 100 LEDs with 50 or 100 driver circuits (Expensive MOSFET drivers). Try to get this small enough for a commercial product.

[kpatz]

If you run them at 2-4 MHz you might be able to drive them at 0.1 to 0.15? A. The (pulse) energy output of each LED will be a lot lower then the output in the Blinder. My best guess is you will need around 100 LEDs with 50 or 100 driver circuits (Expensive MOSFET drivers). Try to get this small enough for a commercial product.

MOSFETs rated at a few hundred milliamps aren't that expensive, and in SMD form are small as well. MOSFET arrays could be used to drive a bank of LEDs. The challenge though is gate capacitance, which increases the switching time (and heat generation) of the MOSFET unless you can drive the gate with a lot of current.

Also, the LEDs can be run in series. A typical IR LED's forward voltage is around 1.6 volts @ 100 mA (looking at the Vishay datasheet posted earlier). So, a 5 volt circuit can drive 3 LEDs in series. Bump the voltage up to 12V and you can run 7 LEDs in series from one MOSFET.

The aforementioned LEDs have a rise and fall time of 30ns. So, at a 50% duty cycle the highest practical frequency would be 16 MHz. You could drive those LEDs at a 12.5% duty cycle at 4 MHz.

[fulcrum]

If you run them at 2-4 MHz you might be able to drive them at 0.1 to 0.15? A. The (pulse) energy output of each LED will be a lot lower then the output in the Blinder. My best guess is you will need around 100 LEDs with 50 or 100 driver circuits (Expensive MOSFET drivers). Try to get this small enough for a commercial product.

MOSFETs rated at a few hundred milliamps aren't that expensive, and in SMD form are small as well. MOSFET arrays could be used to drive a bank of LEDs. The challenge though is gate capacitance, which increases the switching time (and heat generation) of the MOSFET unless you can drive the gate with a lot of current.

Also, the LEDs can be run in series. A typical IR LED's forward voltage is around 1.6 volts @ 100 mA (looking at the Vishay datasheet posted earlier). So, a 5 volt circuit can drive 3 LEDs in series. Bump the voltage up to 12V and you can run 7 LEDs in series from one MOSFET.

The aforementioned LEDs have a rise and fall tim e of 30ns. So, at a 50% duty cycle the highest practical frequency would be 16 MHz. You could drive those LEDs at a 12.5% duty cycle at 4 MHz.

Did you actually try to drive LEDs at those speeds? You will soon find out that you will need MOSFET drivers components like EL7104 (see my avatar) etc. to really get the specified rise and fall times out of the LEDs. Don't forget that the specs. of the LEDs are under ideal circumstances. (A couple of them in series is certainly not the ideal circuit for high speed) Driving them in series is very complicated (Probably transmission line design on your PCB) if not impossible for the total circuit you will have to drive fast. Parallel them in small groups with individual (low inductance) smd resistors is much easier. To get these speeds out of the LED, every connection has to be really really short. Simply driving a string of LEDs in series creates a (too) high inductance.

You could try to make the LED(s) part of a LC resonance circuit with a center freq. of 4 MHz, this might work but I haven't actually tried to do this.

I fully agree on your max. frequency calculation. These type of LEDs are designed for high-speed communication applications, and should be able to do just that.

[TurbineDivinity]

Here is a question. would doing it like this other guy said solve the problem?
with 2 sets of leds runing off and on counter to one another? at 1.5 mhz

Could we run them in groups like this in series at higher powers?

Looking at the data sheet for the Vishay leds they put out a crazy amount of power
and look like they can take some abuse.

But would 3 mhz be enough jam a gun?

What if I ran each set of leds at 800Khz counter to one another. This would give me 1.6 mhz and the second jammer head would give me a total of 3.2 mhz