Hi to everyone at DIY Drones!
I don't know much about UAVs, my specialization is the design of laser products. I recently made a laser range finder by accident that might be useful in UAVs.
It started out as a project to design a new kind of chip that can measure events happening at the speed of light. Then, in order to prove that the chip worked properly, I had to make a test bed which turned into a laser range finder.
The chip has programmable performance settings so it can be used for either long range, high resolution or fast update rate measurements or some combination of these factors although not all at the same time. There is no minimum range, it works down to zero meters.
The best programmable settings give:
Best range >100m (to trees and grass)
Best resolution 1cm
Best update rate 100 readings per second
You can see from the attachment that the range finder is quite small. The optics are made from acrylic so the whole thing is very light weight. It has an SPI connection to a host processor or it can have one already attached like in the picture. The laser is Class 1M. The optics are separate from the electronics so that they can be scanned with a servo or mounted on gimbals. It runs from 4.5V to 7.2V batteries and draws less than 200mA.
At the moment I'm looking to see if there is a market for something like this. I might consider producing small quantities for around $450. I'm not based in the USA so there are no export restrictions.
Hi JD, thanks for the kind comments.
Unfortunately, there's no such thing as a "not so elaborated" LRF! :} The main problem is trying to get components to work at really high speed. When you put these fast devices on a PCB they suddenly become noise generators that try to send messages to Mars instead of behaving like it says in the datasheet. ;O
Notwithstanding this, if you think that your electronics skills are up to the task then I'd be delighted to give friendly advice if you need it. But if you're a bit iffy about laying out multi-layer PCBs with impedance matched tracks then rather wait until the SF-02 kit is available and save yourself a lot of pain!
Brilliant design. I've had a look at the 2 datasheets you recommended. They were incredibly helpful.
Excuse my ignorance (I'm new to this laser stuff).
I see that the DS00VQ100 chip never actually performs an A2D conversion, and rather just uses a counter to measure the time between the outgoing and incoming digitized pulses.
I am actually interested in analyzing the return signal to obtain some other data (using the return signal's shape and amplitude) and not only distance. So I'll need A2D conversions and thus I'll probably have to run a chip in the GHz range if I'm going to be getting samples out of such a short pulse (in the ns).
I'm keen to use a lot of your ideas, although I'd prefer to use a Microchip chip as I've had some experience with them.
Do you think all of this would be possible? Any ideas/advice would be greatly appreciated :)
Sounds like an interesting application DJ.
As you correctly point out the technology in the DS series chips is based on digital time-base expansion and they use digital versions of the signals that have passed through a high speed comparator before entering the timing circuitry.
We have other LRF controller/timing chips that work on a different principle. The SF series as used in the SF01 (available now) and the SF02 (coming soon) directly expand the time-base of the analog signal and then use a conventional A2D to store them in processor memory before analysis. Both the analog and digitally stored versions of the signal are accessible to an external processor.
The image below shows what these signals look like. The red line (positive going signal) is the outgoing laser pulse. The return signals are inverted with a baseline of 2.0V DC. The blue line is a saturated return signal from a reflective target and the green line is a weak signal from a dark target at the same distance.
The time-expanded scale of the image when viewed on an oscilloscope is 125ms which equates to a real-time of 250ns. The digitized version of the signal has an equivalent A2D sampling rate of about 8GHz with a voltage resolution of 12 bit.
That looks pretty cool :)
I can see it being useful for terrain avoidance and terrain tracking for UAV's.
Depending on the minimum range, it could be used for precision landing approaches too.
My UAV group spent some time looking at the laser range finders that are starting to appear on cars, but without success. We'd definitely be interested in incorporating one of these into our fixed-wing UAV's, possibly with some APM integration too.