Boe Bot, Ping and do I have a misconception on how they work?

deadwhale

I'm still waiting to get my boe bot, ping and PIR, but I just read an article in ROBOT magazine about the Prop Bot and how it uses ping. Am I wrong
in thinking that the boe bot STOPS to use it's sensors, then runs essentially blind for a bit, then STOPS again to use it's sensors?

That isn't really what I had in mind for my first robot. I was really looking forward to one that could change directions on the roll based on what it 'saw'
in front of it.

Does it take a co-processor like Blue Bell Design's to get around this or can this be solved with a servo controller? Maybe I read the article wrong and
boe bot doesn't need to stop to use it's sensors?

I'm as green as it gets with this stuff, and as I said, I'm still waiting for my first boe bot, so maybe this is just pre-ownership jitters?

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Prune Free.

Ugha

First, I don't have Ping... but I do have 3 boebots so I can tell you about its other sensors.

Your both right and wrong... the BS2 can only do one thing at a time... BUT it can do them VERY quickly. Faster than human perception anyways.

Another piece of vital info is that the BOEBOT's servos require repeated pulses of data to keep moving.

But between these pulses you can do other things... like read sensors.

If you program it right, the bot can smoothly and quickly react to sensor input with no delay.

Thankfully, all the info for the programming is available for download on the parallax site.

As far as the Ping... in most of the movies I've seen of it mounted on a turrent, the robot does indeed have to stop. I could be wrong though.

Mike Green

The reason for the BoeBot stopping has little to do with the Stamp. Usually the PING is on the servo bracket that's designed for it so it can be swept from side to side. If the BoeBot is moving while the PING is being moved and is reading distances, it's harder to make sense of the data since the BoeBot is still moving and the sweep and readings can take a couple of seconds. It is possible to do, but harder.

The Stamp is capable of controlling 3 servos and getting information from a PING. It does this by outputting the 3 servo control pulses, then doing a PING measurement in the remaining time between 20ms servo control pulses. The longest servo pulses are about 2.5ms. Three of them could take 7.5ms. Add a couple of hundred microseconds for a few PBasic statements and that leaves about 10ms for the PING echo. The maximum PING echo time is about 18.5ms, so the servo pulses could be a little late. Most servos will tolerate a bit longer than 20ms between control pulses (often up to 30ms), so this should be ok.