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USA
Asked — Edited

Greedy Robot Arm Video

I thought this.is.useful for grabbing a beer but it didn't say how it worked or what sensors used. Could You direct me to what sensors to buy to utilize this feature?


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USA
#1  
I think we are missing the video or link. :/
USA
#3  
Haha I didnt know that was there.
#4  
Bump , so does anyone know how this works , what dj is using as a trigger?
USA
#5  
Grrr We are blocked from videos at work. I wanted to take a look again but I think there may have been a IR or something like that just beneath the claw. It just grabs whatever comes close. See if there is one.
PRO
Synthiam
#6  
The project can be found in File -> Examples -> Robot - Greedy Arm

For that video (it was only a test) I had attached a sharp IR distance sensor to the top of the claw. A script watched for the distance to be low, then it would close the claw and move the object.

:)
USA
#7  
:) It looked like you were having fun in that clip.:)
PRO
Synthiam
#8  
lol yah it totally cracked me up:)
#9  
@DJ How did you calculate the correct ADC multiplier? (in general actually, not just for this project, what are the proper steps for figuring that out)?

Does the sensor you used have a specific specification, or do you need to use trial and error or an ADC graph or meter to see what the voltage units are when set to 1 and then calculate up or down from there?

Thanks,

Alan
PRO
Synthiam
#10  
Add the ADC control and connect the Sharp distance sensor. Move objects close and write down the maximum value that you're looking for:)
Canada
#11  
Thanks DJ! for the very EZ solution(beer?) to make the claw grab! speaking of beer, Josh was thinking out loud suggesting putting a can of beer Canadian eh! into the gripper and have it "chug" a full can into a funnel feeding an eager frat mouth......ahhh memories:)
United Kingdom
#12  
The datasheets on the sharp sensors should tell you the maximum and minimum distances. Maximum or above is an ADC of 0, minimum or less is an ADC of 255.

The ones I use are 4 to 30cm (GP2Y3A001K0F), so I know 255 is 4cm or 40mm and 0 is 30cm or 300mm.
The range being 30-4 = 26cm.
Which means a change of 1 in the ADC is around 0.1cm or 1mm if calculating it roughly. To calculate it more accurately...

Range/255 =
(30-4)/255
26/255 =
0.102cm per ADC

Bearing in mine IR sensors work backwards to Ping sensors, the closer the object the higher the value. So it's easy to get distance from them.

Distance = Minimum distance + (ADC x Multiplier)

In my case;
Distance = 4 + (ADC x 0.102)

Ex.
ADC = 172
Distance = 4 + (172 x 0.102)
Distance = 4 + 17.544
Distance = 21.544cm
#13  
Personally I opted to try a ultrasonic sensor in my claws , since IR are sensitive to other light interference and some cups/ bottle are reflective. If ultrasonic doesn't work well I will use IR.
#14  
Thanks all. I am going to be using mine to pick up cat toys and bring them back to me (my cat chases, but won't fetch.. I used to have a cat that fetched. Was a lot easier to play with), and this will help picking them up. May even get the robot to throw the toys for her:) (I am going to be such a couch potato when this project is done.. I finally have started to get work done on it rather than just ideas. Got the camera wired to EZ-B so I don't need to charge it last night, got the tread platform completed... Getting my new WiFi board today so hopefully get that working in a day or two. Everything takes longer than I expect though. I thought I would have gotten a whole lot more done yesterday).

Alan
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