Arduino Forum

Topics => Robotics => Topic started by: tnkumar on Nov 18, 2018, 07:40 pm

Title: Kit for building robotic arm with Arduino
Post by: tnkumar on Nov 18, 2018, 07:40 pm
I have ordered my first Ardunio Uno and was conisdering buying ArmUno robotic arm from https://microbotlabs.com/armuno-2.0-desktop-robotic-arm-kit.html

This is available on Amazon for 37$.
I will have Arduino Uno, but do I need to buy anything else?

Can I get any feedback on this arm or suggestions of other robotic arms I can consider?

Title: Re: Kit for building robotic arm with Arduino
Post by: pert on Nov 19, 2018, 01:04 am
I believe this is the Amazon listing:
https://www.amazon.com/dp/B00X3C3ZFO (https://www.amazon.com/dp/B00X3C3ZFO)
You'll need a power supply for the servo motors and a way to connect the servo motors to your Uno and the power supply. They do sell shields for the Uno that have connectors for the servo cables and the power supply.

For feedback on the arm, read the Amazon reviews. The laser cut material of the arm is very flimsy so you will need to be gentle with it. The servos are very weak so you won't be able to lift anything at all heavy with this arm. It's kind of amazing if they can even lift the arm itself. If you just want to play around with moving an arm with an Arduino and don't want to spend much money, it will probably be OK.
Title: Re: Kit for building robotic arm with Arduino
Post by: tnkumar on Nov 19, 2018, 03:56 am
Thanks. That was helpful.
Title: Re: Kit for building robotic arm with Arduino
Post by: Northof49 on Nov 19, 2018, 04:32 pm
If your robot arm is going to be based on servos, and not stepper motors, I would suggest buying an inexpensive I2C servo control board.  They can be bought from China for around $5.00.  They make it simple to have a separate power supply for the servos, and because the board itself generates the servo control pulses, you won't get any of the jitter that you often get from Arduino generated servo control signals.  All servos will buzz when under load, but Arduino controlled servos often shake due to some fault in the way Arduino generates servo control pulses.  The simplest solution is an I2C servo control board that you control with your Arduino.

Although they don't look pretty, I have had good luck with this style of robot arm.  It's fairly strong with the right servos.  Some don't come with the turntable base.  Some sort of bearing stabilized base is critical, as there is a lot of stress on the servo shaft on the base.  In my case, as space is at a premium, I am using a Servo City servo block for a base.

http://www.robo-dyne.com/en/shop/as-6dof-aluminum-robotic-arm-frame/
Title: Re: Kit for building robotic arm with Arduino
Post by: tnkumar on Nov 20, 2018, 10:07 pm
Thanks @Northof49

https://goo.gl/BF9xk7 - Is this an example of an I2C servo control board that you mention?

Also, what are the pros and cons of servo motor versus stepper motor for robotic arms?
Title: Re: Kit for building robotic arm with Arduino
Post by: Northof49 on Nov 20, 2018, 10:54 pm
PCA9685 is the board that I am using for servo control by I2C.  It's cheap, like $2.00 us from China.  Can control up to 16 servos.

Hobby servos aren't as precise as stepper motors, or as repeatable.  Stepper motors with some sort of gearing, like 10:1 geared are strong and very precise and repeatable when microstepped.

You don't have to spend a lot of money for them either.  You can get a ramps 1.4 board for an Arduino along with some A4988 stepper drivers for around $30.00.  They are good for steppers of approx. 1.5 amps.  Not complicated to control either.


Nema 17 size steppers with a 10:1 gearbox are around $50 each.  With microstepping you can easily control their movement to 1/10 of a degree.  Way more precise than servos.  Mine are set up for 89 microsteps per degree of movement.


Take a look at the fancier robot arms, and they all use stepper motors instead of servos.  Some use geared steppers, others use belt drive or external gears to multiply their torque.


It all depends on how strong and accurate of a robot arm you want to build.


If your budget is thousands, you can build something really cool like the AR2 robot arm.


https://www.youtube.com/watch?v=EAcU4k2Qskk

Here is what looks like a pretty good servo driven robot arm:

https://www.youtube.com/watch?v=AGHwW5TSNCY
Title: Re: Kit for building robotic arm with Arduino
Post by: PaulS on Nov 21, 2018, 11:49 am
If your budget is thousands, you can build something really cool like the AR2 robot arm.


https://www.youtube.com/watch?v=EAcU4k2Qskk
Thank you for posting that link. Pretty impressive robot arm, at a decent price.
Title: Re: Kit for building robotic arm with Arduino
Post by: Northof49 on Nov 21, 2018, 05:04 pm
And if you are not into writing your own software, the designer of the arm, Chris Annin has developed excellent software for his AR2 arm that incorporates inverse kinematics, scripts for repeatable movements and reaction to external events and triggers.  I have used the software to control my Dobot clone arm with some appropriate modifications to the Arduino sketch.  It's rare to see such a fully developed open source project for a robot arm.