Devantech SRF08

Created Thu, 23 Jun 2011 06:26:58 +0000 by Mr_Fixit

Mr_Fixit

Thu, 23 Jun 2011 06:26:58 +0000

Greetings all,

Anyone use the SRF08? I have been using it in single echo mode but really want to use its multi-echo capabilities, however I have been unable to get any results that are remotely useful.

Here is a sample of data I am receiving when its pointing to the ceiling 6" above. Command is 0x50, so data is in inches: Multi Echo Starting Echo:0 = 32 Echo:1 = 57 Echo:2 = 82 Echo:3 = 107 Echo:4 = -123 Echo:5 = -98 Echo:6 = -73 Echo:7 = -48 Echo:8 = -23 Echo:9 = 259 Echo:10 = 284 Echo:11 = 309 Echo:12 = 334 Echo:13 = 359 Echo:14 = 129 Echo:15 = 154

Playing around a bit, I have found that the first few echos had some accuracy, but the others dont even when I setup multiple targets.

So, anyone been able to write some code to handle multiple echos? Willing to share? Single echo is ok, but severely hindering.

KM6VV

Thu, 23 Jun 2011 19:27:35 +0000

ceiling 6" above? Kinda close!

How about experiments out in the open, multiple targets?

You might be bouncing around multiple walls...

I have a 6- SRF08 array on the new 'bot I'm working on.

Alan KM6VV

Mr_Fixit

Fri, 24 Jun 2011 03:55:21 +0000

6 feet. :) Yeah, gonna work on it outside and figure this out.

Your bot looks pretty cool! I still have some mechanical assembly/fabrication to do on my bot before I can snap a shot, but you may be able to answer another question for me since you are using the same sonar modules:

What angle should I place two SRF08's so that I get some overlap in front of my robot? My bot is 14 inches wide and would like to be able to determine if objects are directly in front of the bot. If the sonar envelopes overlap in this region then en object in that area should return roughly the same echo on both devices. This will also enable to let me determine when an object is to the left or the right of the bot's path and only use two devices.

KM6VV

Fri, 24 Jun 2011 17:13:31 +0000

As I recall, six (6) SRF08 rangers nicely covered 360 degrees, with little if any overlap. So I'd put them at less then 45 degrees of beam separation. You might actually want 30 degrees.

My "hex" motif and 5" diameter aluminum disks naturally lent to using six sensors. Even a little room left for a Sharp IR sensor next to each (next rev?).

Alan KM6VV

Mr_Fixit

Sat, 25 Jun 2011 05:47:45 +0000

Cool! I am going to toy around this weekend and see exactly what the detection window is at various distances. The chart given is a bit too general. Also going to experiment with limiting the beam width based on information provided on the site for Devantech. This should also help reduce the problem of stray echos.