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View Full Version : [Project] Open source, time-of-flight, laser range sensor



Laser Developer
01-30-2014, 03:15 PM
Just finishing off a project that is an open source time-of-flight laser range sensor (OSLRF-01). It includes the laser, detector, optics, amplifiers and SETS (sequential-equivalent-time-sampling) circuits to convert the outgoing laser pulse and the return signal into slowed down analog images that can be read by a conventional ADC on a microcontroller. There is no signal processing on board. The idea is to use spare processing capacity on a host controller to run simple algorithms that convert the signals into a distance. This helps to reduce the cost.

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There is a more detailed technical description here:

http://forum.arduino.cc/index.php?PHPSESSID=a14euuffj020tc2g96c03tdrm6&topic=213774.0

(http://forum.arduino.cc/index.php?PHPSESSID=a14euuffj020tc2g96c03tdrm6&topic=213774.0)I've also put together a small production run of boards so that people can start playing with this technology. They are available from:

http://www.lightware.co.za

(http://www.lightware.co.za)I'd love to get some comments.

jwatte
01-30-2014, 10:21 PM
That. Looks. Awesome!

Question: At $100, and with a custom PCB, is the cost of a $1.30 microcontroller really that much of a problem?

Laser Developer
01-31-2014, 12:51 AM
Thanks jwatte!
I've agonized over the processor issue for more than two years now and I'm still not certain that the current design is the right solution. Apart from the cost, there are some valid reasons for keeping the processor separate:

1. We get many requests from students who want to work with the raw signals - their projects relate to signal processing.
2. Users might not be familiar with the specific processor which would limit their ability to modify the code.
3. Any code in the processor would need to have some specific functions which might not be relevant for a given application. For example, in the picture below there are two return signals - one from a nearby window and the other from a wall outside. In some cases the first return signal may be needed (small robot), whilst in others the second signal may be more important (checking for the presence of a car parked outside the window). Trying to cater for all situations makes for large and complicated code.

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4. It is difficult to define appropriate interfaces for a processor based system, everyone seems to have their own preferences and putting in too many interfaces makes the unit expensive e.g.. USB, I2C, SPI, HART, CAN, 4-20mA, relays, displays, LEDs, analog voltage etc.
5. We want to expand the open source idea in the future to include scanning capability. The scanning part would need a processor anyway and it seemed a bit redundant to have two processors in such a small system.
6. Finally, you only get a true appreciation of what this laser can do when you see the return signals. I think this is important for triggering new ideas about possible applications and product improvements.

The OSLRF-01 is an experiment to see whether an open source LRF is of any value to the robotics community. We don't know the answer
yet...

jwatte
01-31-2014, 10:40 AM
Seems like you've given it a lot of thought!

Half a year ago I was looking for just this kind of thing, but I then decided to go another direction. I really hope you do well!