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Robotic arm with 7 servos

by jjshortcut, published

Robotic arm with 7 servos by jjshortcut Apr 21, 2010

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Description

Here is my robotic arm made of 4mm hardboard with a 3-axis cnc, it is also printable. The servos are the most cheapest ones (TopLine standard servo RS 2 J/R and TopLine mini-servo ES-05 JR).

A little video:
youtube.com/watch?v=gfsLu1iuLRg

More about the electronics and other info at:
jjshortcut.wordpress.com/2010/08/17/multiply-the-robotic-arm-and-electronics/

About the mechanics:
jjshortcut.wordpress.com/2010/04/19/my-mini-servo-grippers-and-completed-robotic-arm/

Recent Comments

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Great project.sir , i would like to ask, what is the size of the eps file if printed to a paper ?thanks
I used an arduino to control the servos, but for the movie I used just a regular servo setup, the servos connected to an receiver which is controlled by the remote

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Instructions

To assembly you take a lot of m3 nuts and bolts, for the gripper you also need nylock nuts m3. To connect the horns of the servos to the parts you use little screws like 2x10mm (or 1,5x10mm). The "bearings" are connected with double sided tape on the back of the servo. The "bearings" are made of plastic (PVC in my case) so it doesn't have much friction.

The base is made of one servo with 12mm spacers with m3 screw tread in it and some washers. The bottom and top plate are connected with 45mm spacers and connected with m3 screws which are sunk in the wood. The servo horn is connected with some small screws like 2x10mm (or 1,5x10mm) to the servoplate.

The underarms are connected with 2x10mm (or 1,5x10mm) screws to the servohorns and the servo itself is connected with m3 nuts and bolts to the servomountplates. the servomountplates are stuck in the servoplate with a bit of a press fit. Also u could use some glue for extra support.

The upper arms are connected on the servo with 15mm spacers with m3 screw tread in it, as you can see in the pictures.

The wrist is also connected by a press fit and some long m3x30 nuts and bolts to secure the mini servo.

For more support to lift something you can add a 45mm m3 spacer between the 2 servomountplates and a 15mm m3 spacer between the upperarm parts. Then you could attach a spring (or two) between them.
Great project.sir , i would like to ask, what is the size of the eps file if printed to a paper ?thanks
Hey... I noticed on your blog that the servos you were using had four wires coming out. Did you mod them for open loop feedback or did they come from the factory that way? Thanks!
I used the 4th wire for feedback yes, to make it a teach-in robot.
Hi, jjshortcut, I'm very impressed with all your work (especially the CNC machine). Well done.

Sorry to raise the rc control question again but I am still not sure how you are going about it. My understanding is that you just can't take any old controller (say for a car or plane) and a bunch of servos (rc servos?) and then expect to be able to control them just like that. Unless you have taken the motors out of a model that the RC control is for, there is a lot more to it (e.g see superdroidrobots.com/shop/custom.aspx/rc-support-menu/40/)

Is there a motor controller board or some other interface circuitry in your setup? Or are you using rc servos i.e. with a receiver?
I used an arduino to control the servos, but for the movie I used just a regular servo setup, the servos connected to an receiver which is controlled by the remote
Hi, what spec are the motors in (kg-cm) and how did you attach the robot arm to the back of two servos. Thanks!
I'm not sure about the kg-cm, check the datasheet, maybe it specified that, and I used the round bearing things to make a rotary movement, and glued these bearing things to the back of the servo
hi i see yo have a 3d cad it is posible to share it? thank you.
I uploaded the cad files for you! :)
hello would like to know ue measurement units are made planes download them and want to send a laser cut and need to know in measurement units are in cm or mm? thank you very much and if possible I could send a plane but microservos arm
hi i want to make a design like that which program did you use or recommend me! thanks
Hello!
I am making same arm for my final year project and i want to ask a question.

What was the weight of your total arm and to lift of 100 grams what was the torque of your servo motors? (in terms of Kg-cm) (since yours is wooden and mine will be made out of aluminum, it will give me a good guess of weight and type of servos i will be using)
Actually I do not have any idea about the weight..
i was thinking you could make this but use hydraulics(syringes with oil and tubes) that are actuated by servos, that way it reduces the weight of the arm that needs to be lifted and it would just be cool.
Hi friend

I make " handful " but i don't know how to make arm, or rack.
I finished this -> http://jjshortcut.files.wordpress.com/2010/04/img_4269-800x600.jpg

But not other things . 
How you can post a drawing there or on your site, i following you there and also there http://jjshortcut.com
I am making on of these on my laser for a fellow Thingiverse reader and was curious to where people get the hardboard for these projects?
I just got them in my local hardware store.. they might not have actual hardboard 4mm but probably they will have 4mm mdf which will do as well.
Hi,

I've build one and you can read about it here: geekswithblogs.net/kobush/archive/2012/04/09/149258.aspx

I'm now working on the software to control it and plan to blog more about it.

Big thanks to jjshortcut for this awesome design!
What do we need a 3d printer for?
you could print it, and the "bearings" can not be lasered..
Thank you!

and also, is there any way to get the specified servos in the US?
Hi I was wondering if you had burnt out any servos while testing/building this? A couple of my motors were making a faint buzzing sound while not in motion which is apparently a sign for binding. I didn't think much of it until one of the bottom servos (the two at the top of the rotating plate) started smoking. I don't understand what caused it to bind and if this is a problem that will keep happening. The top of the arm is quite top heavy and the movement of the arm is pretty jerky. When I try to get the arm to point all the way up then it's weight causes it to push to one side. Is the servo burning out a precursor to a problem that will keep happening? Any advice on this problem would be greatly appreciated because I am pretty stuck right now. Thanks!
Is the chasis made of cardboard? If not, can you pleases tell me, and give me measurements to make it? :'(
I'm not sure what chasis you mean, you can download all the drawings.
Can you be more specific with the instructions? :)
Seriously, read the drawings, the part list and the description about these questions?.
How many servos will I need? Also, I live in the United States, so is there any alternative servo I could use?

Thanks :-D
Will the structure be made out of wood? :-[
Hello,

I was wondering how I would attach the gripper and would it be remote controlled too? :'(
What are bearings and spacers?

Also, Please say it is remote controlled and if so how do I make the remote control. :'(
I just took a normal rc remote control to control the robotarm, and the bearings are the parts where the arm rotates around. The spacers are ment to make the arm stronger.
Will this robot arm be programmed with a remote control, and if so how do I control the arm and gripper/hand. Also, what and where is a miniservo?

Thank You.
I used a rc remote control but you also can use any type of svp controller. The mini servo is just a normal servo but a bit smaller, these are used for the wrist and gripper of the robot arm.
Hello again, I have been working on your arm and it is coming along nicely. An issue I have run into is I am unsure of how to attach the other part of the elbow (the side that doesn't have a servo). I saw in your video that you had some black piece there, and I was wondering what those pieces are and how you did that. I saw that you also used that same thing on the wrist. I attached a photo of how far I am minus the gripper.

I was also wondering where the small circular piece needs to go because I don't want to overlook what could be an important part. I attached a photo of it. Thank you so much once again for all your help!
I am a little confused as to what you mean to do with the circular piece. On the fifth picture it shows a different looking piece so does that mean that I should print the piece out on a reprap because laser cut only does one layer?

Also on the part of the robot where you attach the elbow servo and wrist servo to the arm and hand I was wondering what you do to the other side that is not directly attached to a servo that is on the backside of the servo that will still be able to rotate. I saw that in your video that you had tw
o black pieces but I can't see what they are from the angle. I attached a photo of the side that attaches directly to the servo, but I was just wondering how to attach the other side of the piece to the arm without a servo??
The circular piece is the piece which is on the 5th photo, this is the black piece of the video. It cannot be made by a lasercutter no, but it can be printed. This part is taped or glued to the back of the servo as said before, and the one-hole of the underarmleft (or right) part fits on the black part (as a bearing).
Hi, the 5th picture of above shows the circular part, this is the bearing thingy which is on the back of the servo. It's actually a bearing together with the hole in the long part. I taped it to the back of the servo with double sided tape. The "bearing" piece has to be made out of plastic actually otherwise it wil not work that good. Hope that helps!
hai friend,very nice work, i'm also starting the work of thi arm. i'm planing to buy servos of 3KG is that sufficient??? i'm using pvc sheet of 2mm.
I'm not sure it is enough, I do not know what you want to lift... Also, the pvc sheet might be to thin for the arm.
Hi great project! I want to make a robotic arm for a project at school and I have read though your wordpress and have watched your video. I was wondering because I see that you are using what looks like a normal RC transmitter in your project but you have 7 servos hooked up. Did you use connect some of them to the same channel with splicing? I was wondering because I have a five channel transmitter and was wondering if that would work. Also I saw that most of the servos you used are standard. But, the servos you used are not sold in the US sadly, but I want to use something similar or with more power to lift heavier objects. Would you recommend using high power 90 degree servos for the claw and such and 180 degree servos for the rotating base? I was also wondering where you got your 15mm and 45mm spacers from, or could I just use a combination of 5mm and 10mm nylon or aluminum spacers to get the space desired? Sorry for all the questions. I am a beginner to robotics and don't really know where to start. Thanks!
For the demo video I used a rc transmitter yes, I connected the 2 servos of the 'elbow' of the robot to one channel. So the elbow actually only needs one control signal. With your transmitter you can only control 5 servo's...

For the servo's you can use just regular servo's you can find, it doesn't matter that much. But for some more heavy lifting you should need stronger ones. And for the gripper I used just normal servo's, 180 deg. I do not think it makes a lot difference 90 or 180, it doensn't use the whiole range o
f 180, but it might be that 90 deg. is to less.. Not sure.

For the spacers you can use anything, I just like the nice metal or plastic spacers.
HI cool project what size sheet is the Whole robotic arm drawing on ????????????? :) :)
To JJ

I am in my final year BTECH in electronics and communication . This is my Final project .Have done it only because of ur support through thingiverse.Hope u like it.

I have used part steel and part wood for weight consideratons and also have attached a spring.I am using a 16servo usb controller
Nice! Really cool to see, and it looks like a good controller you made!
i made de arm but i have a problem the arm is so heavy, the arm fall , i am change servos for a 13kg/cm stall torque, is beter but not solve a problem , im use 6mm acrylic board and a power suply if 5v and 4 A, i have some pictures, i think the acrylic board is much heavy for this project. what you think about

thanks and sorry for a bad english
Nice robot arm, looks cool. For the problem of the weight you can try to add some springs to compensate the weight.
thanks, i am try the springs and report lather
from ur pics it seems to me that u r using a 7805 voltage regulator ..it supplys a currnet of 1 milli amp.not enough to hold the motors tight..

try using 7806 coz it will supply u 1 ampere of current enouh for motors.... also remoe the screw on the voltage regulator and connect a heat sink to

hope the spring and change of supply must help u

coz i did the same (will upload the pics in few hours )
thank sumanta, but have a jumper to by pass the voltage regulator i am by pass because the limit o current.

i am have buy a pololu usb servo controller, because have more opition and programing opition

Thank for help
hi again,

i have finished my hardware part ... i need to know how to reverse the servos,as the servo motors rotate only in one direction

thank u
sumanta
hi,

I'm not sure what you mean, the servo's do not have to be reversed? You give them a position to go to.
hello,

i am trying to control the servos with a Microcontroller ....and i am only able to rotate it in one direction as u said by assigning proper pulse width ..but i am not able to rotate the horn in other direction ......for example the base , if it rotates in right side i am unable to bring it bacck t
o left with programmin support..(this is wat i meant by reverse )
Hi,

Í don't know what microcontroller and what programming-language you use, but you should connect the servo as it is in the middle of it's range. This way you can use 1/2 of it's range to move to the left and the other 1/2 for steering it to the right.
Would you be able to upload .eps / .svg files to accompany the .dxf file? There are more free tools that can work with SVG and Ponoko accepts it as a format for laser cutting. Thanks regardless though, it's a cool design and I really like the gripper.
Hi,

I converted the DXF file to .eps with Inkscape which can convert DXF files and is freeware.
Ah, thanks! I'd spent time trying to figure out what could process .dxf files and hadn't realised that Inkscape could already do it natively! Excellent, thanks!
hello;

i am making one of this with 3mm ss.can u suggest a possible way to connect the upper right wrist to the upper right arm.

as the left side of the upper arm is connected with a servo to the left wrist .....

i am out of ideas here ...

thank u
Hi,

I don't know how you are making the arm, printing, milling or just by hand but the bearings are print-able or mill-able.

If you are making it by hand there must be something like a plastic part which would work like a bearing..
hello,

I made one out of ABS sheet 3mm. it works fine.

I changed a piece and added a GP2D12.

Programmed in vb. It can play against an AL5B from Lynxmotion.

all is handmade :(

youtube.com/watch?v=he5dLcto_P0
What scale is the dwf file set to? I'm trying to print it full scale and can't seem to be able to do it.
I'm not totally sure what you mean but it's drawn in mm and its 1:1.
hi,i work in a robotic arm with you files and instruction, but the mechanic parts made in acrylic plate, and i use a circuit if a PIC 16F628A for control movements of robot arm, soon i have photos and video to post for you thank for your post

sorry for bad english, i from brazil adn english is not my natural language
cool, I'm looking forward to see it!
This looks very cool. What kind of weight can it lift? Are all of the joints just using plastic spacers to reduce friction?
I used plastic "bearings" at the end for less friction yes, for the weight it can lift, I think about 100grams but it depends on what servo's you use, and if you use a spring for weight compensation U can list more.
I made one of these out of aluminum and it works pretty good (except for my code moving it) I have a video and some more info about it here robhopeless.com/
Wow! Seriously really cool!! :-D
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