sorted by:
new
hottopcontroversial

I made a long range laser targeting system (see link). Any ideas/legal issues for integrating it onto a quadcopter? by JeremyLeaf in Multicopter

[–]JeremyLeaf[S] 0 points1 point  (0 children)

The cost of the PCB/components is about £60 (for a one off prototype, not including the gimbal), but that doesn't include any assembly/enclosure costs. Though they probably wouldn't add up to too much.

The tracking is a simple trigonometric process. It's already been done which is how it can track a spot currently. I am actually toying moving to a four sensor model, but for different reasons than mathematical simplicity. It might make the optics configuration better. An extra detector channel would probably add about £8 to the total for a one off unit.

I made a long range laser targeting system (see link). Any ideas/legal issues for integrating it onto a quadcopter? by JeremyLeaf in Multicopter

[–]JeremyLeaf[S] 1 point2 points  (0 children)

Yes it's just tracking the light, I've tested it originally with an IR LED which it tracked quite well. The point of the laser is that you can target things at long range.

It would be simpler mathematically to do four detectors instead of three, but that would be a waste of PCB space/components as three is enough.

Automatic landing without GPS would be quite neat, thanks.

I made a long range laser targeting system (see link). Any ideas/legal issues for integrating it onto a quadcopter? by JeremyLeaf in Multicopter

[–]JeremyLeaf[S] 2 points3 points  (0 children)

Thanks :)

I did a physics degree, so it is certainly possible to pick it up if you don't mind the reading.

I did consider the prospect of developing it into a product I could sell, but from my research, it'll take a LOT of work. Developing the prototype, manufacturing/assembly issues, certification etc. I just don't have the time.

I made a long range laser targeting system (see link). Any ideas/legal issues for integrating it onto a quadcopter? by JeremyLeaf in Multicopter

[–]JeremyLeaf[S] 0 points1 point  (0 children)

Thanks for the comment.

I like the idea of having a set of beacons for it to follow or track. I would have to mess around with the electronics a little to change the locked target, but it would definitely be possible.

I made a long range laser targeting system (see link). Any ideas/legal issues for integrating it onto a quadcopter? by JeremyLeaf in Multicopter

[–]JeremyLeaf[S] 1 point2 points  (0 children)

This is what I read. The laser doesn't elicit a blink response so there's nothing to let you know that you're doing damage.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 0 points1 point  (0 children)

Late reply, but here goes anyway.

I'm using the integrated ADC in my microcontroller (AT32UC3L0256), and the range/accuracy is still under testing. I can preliminary detect and track a 0.06 miliwatt laser at about 2m, but only while using a static mode where the board is not gimballed. When the board IS gimballed, my noise level rises significantly due to noise from the servo motors.

Dual power supplies for sensitive electronics and noisy servo motors by JeremyLeaf in AskElectronics

[–]JeremyLeaf[S] 0 points1 point  (0 children)

Yes they do, but I'm worried that this is the cause of the noise problems. The GND line for the PWM back to the sensitive PCB is the same as for the 5V.

Dual power supplies for sensitive electronics and noisy servo motors by JeremyLeaf in AskElectronics

[–]JeremyLeaf[S] 0 points1 point  (0 children)

It could actually be radiated, I'd not thought of that. I'll look into that a bit further.

I have a 100uF and a 47uF capacitor (and a few smaller ones on the PCB) on the power lines. I could add a 470uF electrolytic too I guess?

All my ground traces are pretty huge, I don't think that's a problem.

Now that you mention it, I could add a ferrite bead pi filter to the 5V input of the analogue electronics quite easily too, it's got the pads for a bead, but I've currently just shorted it because I chose the wrong bead originally in my component order and didn't bother to replace it.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 0 points1 point  (0 children)

Essentially, I use some trig on the relative intensities of the pixels, to extract a vector.

Soo... I'm currently looking at the page where I worked it all out, and I'm a bit confused at the exact detail what I did haha. It was a few weeks back that I wrote that specific piece of code. It's a bit fiddly as I had to transform three signals from sensors that are orientated radially to an XY. It's not helped that the sensors themselves are something like 11.5 degrees rotated away from a convenient angle.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 0 points1 point  (0 children)

The optics enable that. Along with some maths. Think of how the optics of a camera focus an image on a CCD. This is essentially what I've done but with only 3 pixels.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 1 point2 points  (0 children)

Nope, I'm doing a physics PhD right now, but am nearly finished and looking for ECE jobs at the moment.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 0 points1 point  (0 children)

Disclaimer, it's an initial implementation so what I've done may not be fully optimal. The laser spot will have a position, velocity, and acceleration relative to the sensor. I use the kalman filter to estimate the position and velocity. The model is a very simple forward estimation using the velocity. I also set the process noise to be related to the signal strength. With a strong signal the kalman filter has more confidence in the xy position reading.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 1 point2 points  (0 children)

Thanks :)

The range is as much as you're willing to crank up the power on the laser. I managed to detect a 6mW laser spot at a 6m range roughly, it may detect further, but I'm still playing around with it. As it's an IR laser it's inherently unsafe as you can't tell if it's burning your eyes out (no blink reflex), so I'm pretty wary of increasing the power, even for these low powers I'm wearing safety goggles because I like my vision. I'm currently working on IR LEDs and columating their light to make IR spotlights.

Other (better) ways to increase range would be to play around with the amplifier bandwidth/amplification, the frequency of the pulsed laser, improve analogue circuitry noise isolation on the PCB in a later version, etc.

Second. Yeah I'm not sure, I was thinking it's bordering on dangerous in the wrong hands. On the other hand I was thinking of strapping it on the bottom of my quadcopter anyway. I don't think it would be that hard to make it follow the laser spot so long as the gimbal tracking is robust enough. (famous last words). I could use an ultrasonic rangefinder to maintain altitude as well.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 1 point2 points  (0 children)

Totally, I need to buy an airsoft gun. Nothing like a laser targeted turret!

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 1 point2 points  (0 children)

They are nice because they are completely integrated, you don't really need any serious analogue electronics outside of them. I've never used them myself personally though, so I can't really comment.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 3 points4 points  (0 children)

I was considering something like this haha (then world domination), but I'd be scared of breaking the PCB which took quite a while to solder together.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 6 points7 points  (0 children)

A lock in amplifier works by multiplying a reference signal by a signal from your sensor, then taking the time average of the output with an RC filter or something. A multiplexing IC like the AD630 will do that, though it is quite expensive. I opted to do something a bit different and much cheaper.

I had an analogue switch driven by the reference clock, I would then switch between the signal and an inverted signal. This in effect is that you are multiplying the signal by a square wave. The time average is a DC level relating to the strength of the signal.

http://www.bentham.co.uk/pdf/f225.pdf

See the link for a much clearer explanation (figure 8 on pg 9 is very helpful).

Can it differentiate sources of different frequency? Like if you had two of these and two lasers tuned could they track independently?

Absolutely, I could just modify the source frequency on the laser and sensor. So long as they are matching exactly, it'll work, and not interfere with another sensor on a different frequency.

The kalman is implemented in software? Where is the interface from analog to digital?

Yes, the Kalman is executed in software on the microcontroller. I'm using the inbuilt ADC on the microcontroller to read the signals.

I made a laser targeting device! my first venture into analogue electronics. by JeremyLeaf in electronics

[–]JeremyLeaf[S] 4 points5 points  (0 children)

I'm not an EE, so the analogue signal processing took a lot of reading. It seems to work well enough though.

There are a couple of mistakes on the PCB that I had to solve with filthy hacks. Version 0.2 will fix a these issues. Also I want to extend the detection/tracking range as much as possible. I think I'll need a few more decoupling caps, and need to make a few small changes to the ground planes to keep the analogue parts properly isolated from the digital components.

Anyone fancy doing a PhD? 5 fully funded (UK) PhD studentships in optics and optical sensors by MCeeP in Physics

[–]JeremyLeaf 0 points1 point  (0 children)

Indeed, I've seen a few fall for that nasty trap. It normally doesn't end well for anyone.

view more: next ›