Neato LIDAR Schematic!

A small first step to an open source LIDAR based off of the Neato XV-11 LIDAR...

Below is a first revision schematic of the Neato XV-11 LIDAR Piccolo board.  It was created by hand and I will post a video later explaining how it was done for the curious.  For the seasoned veterans just take a look at the schematic.

Some components were easy to identify and others were not so easy.  The transistors are basically a best guess based off of the minimal identifying marks on the SMT package.  I am not 100% sure how the laser diode control circuit works at this point so I will take some measurements of a live module to test my assumptions.  Based off what I know so far the cathode of the laser module is pulsed to power the laser and it is held slightly above 0V and then lowered closer to 0V momentarily to rapidly turn the laser on and off.

Stay tuned for a video explaining the whole process along with more details.  See CAD file at the bottom of page for raw schematic which was done using TinyCAD...  FREEWARE!!

 

TinyCAD Schematic File 

Laser Pulse Analysis

I have seen on a few forums where people discuss safety issues related to the laser used in a LIDAR. How long can the laser be powered on, etc. Mostly concerning eye safety so you don't go blind!

I setup a test with the Neato LIDAR so I could measure the laser pulse while the LIDAR assumed it was rotating at 300 RPM. Using a microcontroller (msp430F1232) I simulated the pulse train that is normally received by the Piccolo Board from the slot sensor. This meant I could connect the scope to the LIDAR and take some measurements.

Here are a few pictures of my test setup and from my notebook on what I found.  Keep in mind until I determine more about the laser module this information is incomplete.  I'm just getting warmed up!

The test setup...  Black box above the breadboard is used to supply the 3.3V for the Neato Piccolo board and supply the simulated rotation signal.  The small red board on the breadboard is a FTDI board feeding data from the LIDAR into my PC.  

Laser is pulsed on for 200uS and off for 350uS while operated at a simulated 300RPM.

Scope probe in the back of the module measuring laser feedback photodiode.  Wires from the Piccolo Board are soldered to a header which is placed in the breadboard.

Some information about the LDS HORIZ BOARD which the Piccolo board and module above mounts too.  Pulse train shown at the top, notice the start is a half long pulse followed by 14 full length pulses.  This is how the module determines its rotational speed and makes adjustments to the motor speed which is spinning the module.

Observational data about the laser pulse, maximum and minimum rotational speeds that the laser will operate, etc.

Further Disassembly and Analysis...

Check out the video for detailed shots of the innards...

Reverse Engineering the Neato LIDAR

The next couple blog posts are going to be a complete tear down of the Neato LIDAR PCB's.  Every component will be removed and measured.  The PCB will be photographed, scanned, and schematics for the PCB will be created.  All original files are available in a zip file at the bottom of this blog post.

I have started with the LDS HORIZ BOARD which is the PCB that rides under the Piccolo board.  Each component was removed and measured.  I then searched Digikey for a comparable component and noted the part number and description by the designator in an Excel spreadsheet.  These parts have been ordered from Digikey and will be used to repopulate the PCB to verify they are correct.

The schematic was created using TinyCad since I wanted to make sure I used open tools.  I was going to try to create this using Upverter but I think their tool might not be stable enough at this point.  Hopefully I can export from TinyCad and import into Upverter later.  Their collaborative model looks like a great idea!

 Parts above have been ordered from Digikey to verify research and will be used to repopulate the PCB and test.

 

 Here is the top of the board before components were removed

Bottom of the PCB before components removed.  The entire bottom is a ground plane which isn't very special, but it is only actually grounded at the Opto-Slot sensor and at no other place is it connected to the top layer ground plane.  This basically makes it a very large antenna, seems they would be better off with no ground plane on the bottom at all.

 

Scan of the top of the PCB with all the components removed

 

 Scan of the bottom of the PCB with components removed

Download Files in compressed ZIP

Neato XV-11 LIDAR Disassembled... COMPLETELY!

Someone had to do it...  Might as well be me since my Neato XV-11 was paid for by the hacking contest bounty.

LIDAR board pressed into Play-Doh and ready to go under microscope

 My wives microscope I got her for Christmas...  Or Birthday...  Not really sure, just glad I did!  :)

 Back side of lens assembly, I was amazed there are spots on the filter there, must not affect performance that much.

 Same thing from a different angle.  That flat black plastic piece pointing out above the reflective filter looks like it was scraped with something.  Those are little plastic shavings still loosely attached.  **EDIT** Thinking this over a little more what I believe Neato has done is make this opening fit the Panavision sensor EXACTLY.  This ensures that even if the sensor is at a slight angle on the PCB, it will still be centered behind the lens.  This is probably press fit into the plastic and then screwed/glued together.

 Bottom of lens assembly that is screwed to the PCB below.  Looks like Neato included some spots for set screws in the bottom that were not needed under the lens and laser module.

Board that the LIDAR mounts too with optical sensor on the bottom for rotation position.

TI DSP Datasheet

Panavision DLIS-2K Datasheet

Panavision DLIS-2K App Note

Panavision Website