Well it's plywood
I built a robot arm already, but I never liked the gripper. I've been considering buying or building a new gripper. Today I saw this on ebay and put in what I thought was a low ball bid:
http://www.ebay.com/itm/Robotic-arm-DIY-kit-Lasercut-Plywood-Structure-6servos-AT89S51-MCU-USB-ISP-tool-/330853694622?nma=true&si=MZ6wczSDikiabMDwgCtX3vNkafQ%3D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
I really expected to be sniped at the last minute because the battery charger, batteries, and servos alone are worth what I paid. But it also includes a servo controller and plywood arm structure.
http://www.ebay.com/itm/Robotic-arm-DIY-kit-Lasercut-Plywood-Structure-6servos-AT89S51-MCU-USB-ISP-tool-/330853694622?nma=true&si=MZ6wczSDikiabMDwgCtX3vNkafQ%3D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
I really expected to be sniped at the last minute because the battery charger, batteries, and servos alone are worth what I paid. But it also includes a servo controller and plywood arm structure.
Comments
So it's an unasembled kit? all the better.
(to bad it has one of those "other" micros installed though..)
-Tommy
Yep, probably someone bought it and then lost interest. I already have control software from my original arm which should work with this one. So I have options besides the "other" microcontroller. It will be interesting to see what its firmware looks like compared to mine.
The gripper design looks good, as does the wrist, elbow, and shoulder design. The turntable portion looks like it could use some improvement. I think I can also add wrist rotation.
Take photos as you build and write a review for ROBOT or SERVO magazine. Payment will cover the arm plus some beer money.
http://www.ebay.com/itm/330846659304
There's another one of these arms here.
I noticed that to. It's the same seller, so I'm starting to think that the seller is Sawtooth designs who makes the kit.
Yes that seller may be the maker. He already sold two in his feedback section.
I was cruising the day before you bought this arm looking for robot kits, trying to find something better than a rover 5. I came across that arm when the bid was 92 dollars or so. Im surprised you picked it up at just over 100 dollars!! Great deal, that thing looks like a really solid quality arm much better than anything else in its price range.
The firmware probably isn't ramping the servos either. I had major shakes until I added that to my firmware. I also plan to use some of the PowerHD servos from my arm for the shoulder servos. They have metal gears with much better torque than the Futaba servos it comes with. They're also slower which helps keep vibration in check.
I just noticed that it's a 5-axis robot. I counted six servos in the Ebay photo and assumed it was a six-axis unit, but two of those are used for the shoulder. Wrist rotate is missing. It may not seem all that important at first, but after you play with it, you will realize the limitation.
Still a smoking deal for $100.
http://www.thingiverse.com/thing:2433
As you can see they're really similar designs, so hacking it into a six axis machine should be fine. It also has the base plywood and turntable plywood touching to reduce wobbles. I'm mostly viewing this as a way to save time scroll sawing the gripper parts of the Thingverse machine. In the end I'll have a few left over servos from my old arm to repurpose for sensor turrets.
Also, I emailed the seller and he confirmed that he is Sawtooth Design Lab. So this is somebody's ebay robot kit business which is pretty neat.
I think two of these mounted as arms on a (wooden) humanoid robot would be the bee's knees...
I'll definitely document the build and my improvements.
I had to get one, too. Hey, it's plywood!
But I'm fully prepared to be underwhelmed by the included controller. I might have to build one of my own.
Yes, the kit came on Friday, and my son and I finished it this morning. The kit and instructions are well done and everything goes together smoothly. The included controller and firmware doesn't hold a candle to the Propeller inverse kinematics I wrote. The controller is fast enough, but doesn't have enough RAM for trig tables. I wrote the builder and mentioned the idea of using it a serial servo controller with the PC doing the kinematics. He replied that it was an interesting idea.
So I'm going to use my own microcontroller and firmware. I'm going to add wrist rotation in a day or so after figuring out the best way to go about it. I'm not sure what to do with the included controller. It's too nice to throw away, but not good enough to use.
I have a house full of stuff like that!
I am now working on the servo attachment to the remaining part of P2. Basically I'm making a bracket which attaches to them via bolts.
Update : I switched to a mini servo because the length of the gripper plus rotation servo seems to long. A mini servo knocks another quarter inch off which should help.
I agree it was smaller than I expected, but within its work envelope I think it will get the job done. The smaller size might come in handy if you mount it on top of a mobile base too.
http://www.thingiverse.com/thing:387
http://www.thingiverse.com/thing:2902
http://www.thingiverse.com/thing:28969
They all seems to leave out one joint over what is typical (either wrist rotate or elevate), so at this size it might be hard to fit all axis into a machine. I linked to this one above which is about a half servo length bigger and uses mini-servos:
http://www.thingiverse.com/thing:2433
So that extra bit of space may be critical, or may not be. I'll find out as I continue to try and hack in a wrist mechanism.
I'll build mine stock (5 axes) first anyway. But two changes I'll implement at a quick glance:
1) the "gears" that keep the gripper links in sync are nothing close to involute gears and have lots of slop. Pretty bad. I can build up with CA and hand file to a better shape.
2) flipping the gripper over so the servo is on top allows the gripper to be parallel to the ground at ground level.
Yes, it looks almost exactly like the old Lynx 5.
http://roboticseng.blogspot.com/2009/08/top-ten-reasons-to-buy-industrial-robot.html
The Lynx 6 is similar but has wrist rotation, but is just a hair bit bigger.
http://www.robotmatrix.org/images/Lynxmotion-Lynx-6-Robotic-Arm.gif
If the wrist rotation doesn't work I have a back-out plan to add a cross member to bolt the gripper to. That will return to 5 axis, but make the gripper removable for use with my other robot arm. I agree that flipping over the gripper is a good idea. You almost never bend the gripper backwards, but often want to get low to the ground level for grasping.
Martin: Did you try the included controller? I don't think I will. I don't need another uC language on my PC. Besides, I think I'll be busy this weekend "doing the 8" on the PC...
Sadly, not figure 8 challenge. Windows 8 "upgrade". ACK! I have at least 3 computers which might need it.
Microsoft claims the download price jumps from $40 to $200 on Feb 1: http://windows.microsoft.com/en-US/windows/buy?ocid=GA8_SEM_BNG_Buy_Search_Txt_Desktop&semid=ef_BNG_e_x4f51lmge0cdgas4u8i8_2016642753&WT.search=1
I would definitely like to see the gripper mods. I've noticed that the nuts work lose as the gripper moves and was thinking of either switching to lock nuts or putting a bit of loctite on them.
I fiddled a bit with the included controller. It's an Atmel version of an Intel design and it's programmed in a 16 bit integer C. It has 4 kb of flash, but the free tool chain only allows 2 kb programs. For simple stuff it works fine, with the built in UART and some fiddling around I could probably make it into a serial servo controller. But it can't compared to an Arduino or Propeller chip which are both capable of floating point arithmetic and trigonometry.
I'm probably going to hold off Windows 8 until the first service pack and only on new hardware. I generally don't upgrade once I have a working configuration because I am always concerned about drivers on new OS's for old hardware.
It DOES fit inside! Just barely... It was a very quick build using CA instead of wood glue.