Forum Posts

duanemclemore
Feb 03, 2022
In Questions
Hi all, I've always had trouble with the flimsiness of the limit switches on my AR-3. While I know enough electronics to hack things together, I'm not an expert, but I had a question. As part of my research I've purchased a 3d Printer for clay, and it uses Proximity Sensors for it's end stops. I've been quite impressed with their performance. So my question is, from an electronic standpoint is it relatively simple to replace the limit switches on the AR-3 with Prox Sensors that would achieve a similar or superior accuracy and repetition? From the mechanical side, affixing a magnet or piece of ferrous metal and getting it to work from that perspective are no problem, and I -think- I've correctly identified a way to do it at each joint. It's just the sparky side of the equation I am not so adept at. Thanks in advance for any input you can offer!
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duanemclemore
Aug 09, 2020
In Questions
Hi All, does anyone have any tips or concerns to watch out for when removing the lower arm? When I got to the end of my build, J3 had an extreme amount of play. I thought I tightened the bearing tension screws properly when I assembled it, but who knows - maybe I forgot to loctite them and they worked out or something. The chain is tensioned properly and the sprockets and motor don't have any play, this is in the joint. I assume I'm going to have to remove the J4 Motor and mount, then the rest of the arm to access the set screws and tighten them back up. Has anyone seen this before? If so, is there any part of the assembly that may be causing this I'm not understanding? I say this because accessing the J3 bearing tension screws is a bit of an operation and I don't want to do all that work only to find out they're still fine and some other factor is causing the looseness. Thanks in advance for any advice.
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duanemclemore
Aug 09, 2020
In Questions
Chris, have you thought about a design for the J1 Limit Switch that puts it in a horizontal orientation and uses a 3d printed ramp on the base of the J1 Carriage to trip it, rather than the metal stud? Because of the tight fit for the J1 Limit Switch in my build, when it's tripped, it can push the switch itself, bear on the wires, break the DC circuit, and trip the Teensy to off. Which is... less than ideal. (Tighten the attachment screws too far and they keep the Limit Switch from operating) Modeling the ramp is no problem, figuring out the best switch attachment is a bigger question. The orientation would be simple - the leads would come off the side (left when facing the switch from the back) rather than the bottom. For mine I think I'm going to 3d print an adjustable collar to go around the J1 Turret Housing.
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duanemclemore
Aug 09, 2020
In Questions
J2 has a weird issue which may be encoder related - I go through the calibration sequence and when ARCS says it's back up at -90 degrees it's only at about -45. I will switch one of the encoders with one from a different joint to see if the issue is the encoder itself or something else. Has this been observed before, and if so is there something else it could be that I'm missing? Thanks in advance for any help. I'll post the results of the encoder body switch here once I do it in the coming days.
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duanemclemore
Aug 09, 2020
In Robot Builds
Hi all, I'm excited to be posting here. @Chris Annin has been an absolute rock star, not just for designing this amazing platform, but also for answering my whiny, pestering questions over the last few weeks during my build. Thanks for everything Chris! It's very preliminary, as I have bugs to shake out, but I wanted to share a few images of the AR-3 I'm building as part of my research here at Mississippi State University. I'll probably be fairly regular here as 1. I have some build questions I need help with which I'll be posting in that section 2. This build has gone so well that I am hoping to run a Directed Independent Study class in the spring for students who would want to build another AR-3 and 3. this seems like a crazily knowledgeable cohort. There are areas within the research for which I'm using my AR-3 where I could probably use everyone's expertise. So this is from before I started on the controls enclosure (now complete), but it shows the arm in its finished state. Excited to see everyone's builds and share my own. More soon! Duane
AR-3 in The 'Sip content media
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