v2.5 Kit Brass LED's


#1

My new v2.5 kit came with 2 brass encased LED's, but I find nothing about them in the instructions? Did I miss that somewhere?


#2

i would guess they are lasers...


#3

You are correct.:

http://laserpointerforums.com/f52/bulk-3v-5mw-mini-red-lasers-82275.html

Did I miss the instructions from the kit to install them somewhere?


#4

i dont think its that documented yet. but they are intended to be installed on each side of the camera, its been showed in one of the Developers call recently.

wiring wise im not sure how they are connected on the 2.5 but i guess they are on P2 + and - next to the light output.

make sure to find out if the lasers are 5V directly, or if they need a current limit resistor for working on 5V. the P2 is 5V out.

see if there are some marking on the lasers that you can google to find the forward voltage and current, and then use this to calculate a resistor as you would on a normal LED bulb.


#5

Thanks, I'm pretty sure they're 3V so I'll adjust accordingly. They operate just fine at 3V and I have read that they have been bricked at 4.5V.


#6

100ohm in series is probably good, then you'll drive it at 20mA

ref: http://led.linear1.org/1led.wiz


#7

Hi Scott:

As Thomas said, they are lasers. They're supposed to mount on the two indents of the camera plate that are 10 cm apart. If they were in the instructions, it would be at the tail end of what is currently step 58 on Dozuki.

If aligned parallel, the lasers allow you to estimate the size of objects, based upon the two spots that are projected onto it.

We're still trying to figure out an easy way to mount the lasers that keeps them in good alignment- right now it requires a lot of fussing. Over time, there may be some changes to the camera plate (perhaps the addition of a small doubler) that helps to keep the lasers aligned while you epoxy them in place. Ideas from the OpenROV community would be very welcome here.

As Thomas suspected, the lasers wire to PWM2+ and PWM2-. Eric can correct me if I'm wrong, but I believe the lasers are designed for 5V input (there is a dropping resistor on the laser package itself), and that's how the PWM2 channel is set up.

I haven't looked at the 2.5 beta software, so I don't know what's in it for laser support. Eventually there will be a control in cockpit similar to what's there for the lights.

Hope this helps.

-Walt


#8

Thanks for the feedback. Here's how I'm going to try the alignment:

1. Create a cardboard cutout of the camera mounting plate to the exact dimensions. Make sure the two indentations are accurately represented with a marker.

2. Get two 25' strings and tape them to each side of the mounting plate and the replica and stretch them out to where the two strings are parallel.

3. Tape the power leads to a 3v battery (I have lots of CR123A's for military apps)

4. Aim the laser to the replica mark and fix them it place. (Hot glue?)


#9

I picked up a couple of lasers from Eric on my last visit. I could see that the lasers on his demo OpenROV were very bright and when up close would probably be a bit too bright for my taste. What I would like to do is the following:

1) have a manual control of their brightness from the cockpit.

2) without image processing, have some manually controlled cross hairs whose separation can be adjusted by +- increment keys until they overlay the laser spots. A simple algorithm would display the range in big numbers in the cockpit display corner.

3) with image processing, track the laser images and automatically determine range. The lasers I suspect could then be intermittantly flashed like a motion picture camera so that they barely appear in the camera...but just enough to determine range. E.g. every 2 seconds flash them and determine range. The range points could then be exponentially filtered to smooth the display. I don't know how much OpenCV code takes up on the Beaglebone or whether the 2.5 + betas have enough memory to load it. I know that Angstrom had it loaded but Ubuntu requires it to be loaded. Assuming OpenCV is available, it is a simple process to measure the angle between the spots and compute range. This is something I plan to work on once we get the 2.5 stuff up and running.

What do you think?


#10

I'm doing my first build and have been trying to figure out how I was going to mount/align the lasers. I had an idea, but wanted to get feedback here first.

How hot does the brass get? What if the lasers weren't put in the indents but rather was put behind the camera plate thus using the face of the laser to square itself agains the plate and vertically against the support as shown in the picture.

Obviously they wouldn't be 10 cm apart anymore but as long as its a relative measurement anyway, and you know what your starting with, that should work right?

My only fear is that the brass doesn't get too hot and melt the acrylic.

Thoughts?

1103-photo.JPG (101 KB)