Robot arm control electronics

[edgas10]

hi there , i have a new project that is a robot arm ,just a small one enough to move a microphone.
my question is on the electronics, i want to drive it with stepper motors.
does anyone know what kind of board or interface that i can use to manually control(without softwareand computer) the five axis ?
i ve seen boards on ebay with lcd dro and a remote but dont know if it works
thanks looking forward to hear from you guys
thanks!

[Fivetide]

Hi edgas10 welcome to the forum, some of us mess about with Arduino check this link out

Control an OWI Robotic Arm with Arduino
(http://www.instructables.com/id/Intro-and-what-youll-need/)
I have used cheap servos off ebay for my tank which (when finshed) 6 movement axis.

oh and its a cheap way of getting into controls. and lots and lots of add ons.

[edgas10]

hi thanks for your help , i dont think servos would be the best option .
they are not precise and lack of power is a problem too
i have a cnc machine made by me and i want to use steper motor because they have power and are precise.
i want to make my robot in aluminium cut im my cnc machine .
the idea is get a interface board that doesnt need to be connected to the computer to drive stepper motors .
thanks very much

[edgas10]

hi thanks for your help , i dont think servos would be the best option .
they are not precise and lack of power is a problem too
i have a cnc machine made by me and i want to use steper motor because they have power and are precise.
i want to make my robot in aluminium cut im my cnc machine .
the idea is get a interface board that doesnt need to be connected to the computer to drive stepper motors .
thanks very much
oh and i forgotthis:
this is for studio recording so for diferent bands i need that the positions can be stored, to be easely adjusted.

[Robin Hewitt]

i dont think servos would be the best option ... i want to use steper motor because they have power and are precise.

To do it properly you need to gear the motor right down using backlash free components. That means the motors need to be DC, low inertia and powerful at all speeds. There really is only one choice, Google for pancake motors :untroubled:

[D.C.]

this is for studio recording

And you want to use 5 electric motors in there? That hum?

Servos are still your best option for precision, the whole point of servos existence is to provided reliable positioning and they come in many, many different sizes and gear ratios.

[martin54]

There seem to be a few guys on the forum who are interested in stuff like this so it might be an idea to elaborate on what you want to accomplish. More detail you can give people the better placed they will be to help, unless this is an idea you don't want to share just now.

[edgas10]

i think i´ll will use dc geared motors. low noise and power, i dont need speed.
but i still dont know how can i control all of these servos.
is it possible to get a board were all of this is connected and use pots to move each axis?

[edgas10]

whhat do you think about this motor
High Torque Turbo Worm Geared Motor DC Motor GW370 12V 2rpm | eBay (http://www.ebay.com/itm/High-torque-Turbo-worm-Geared-motor-DC-motor-GW370-12V-2rpm-/151005276159?_trksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3 D1%26asc%3D27%26meid%3D6173961592109455582%26pid%3 D100033%26prg%3D1011%26rk%3D3%26sd%3D260775049460% 26)

[D.C.]

I personally wouldn't use those for anything. They are expensive and I can't find a spec sheet anywhere.
I've found a very similar looking motor that is 64 rpm instead of 2 rpm:
Free shipping.12V/64rpm/2.5kg.cm dc Gear motor,dc worm motor,Electric windows motor,micro motor-in DC Motor from Industry & Business on Aliexpress.com (http://www.aliexpress.com/item/Free-shipping-9-12V-dc-Gear-motor-planet-gear-motor-dc-motor-Electric-windows-motor-micro/458865282.html)

And that has some specs. Look at the price, look at the torque and then compare it to the specs for the mg996r at servo database:
TowerPro MG996R Servo Specifications and Reviews (http://www.servodatabase.com/servo/towerpro/mg996r)

Forgive me as we don't have a lot of information to go on but do you understand, what dc motors, steppers and servos are and do you know how each of them works?

Try watching this video:

https://www.youtube.com/watch?v=-XSXfqd1N58

A servo is just a DC motor, geared down with an absolute positon device and some control electronics. Sure you could use steppers to do what you want but as you design it you will figure out that:


for diferent bands i need that the positions can be stored, to be easely adjusted.

You need to store the microphone positions, this means you need a computer. The computer can be a normal big box PC that you are familiar with or it could be a micro controller like an avr or pic (ie an arduino which has already been suggested).

In order to move from position A to position B, you need to know where the microphone actually is in relation to positions A & B. You can use servos which already come with this feature built in or you can use steppers and spend a load of money and time creating your own custom absolute position encoder.

You need a way of translating real world microphone positions into positions of 5 motors, welcome to Inverse Kinematics.

Arduino Robotic Arm with Inverse Kinematics - Towers of Hanoi - YouTube (http://www.youtube.com/watch?v=7XVKunv61iM)


If you aren't happy with the performance of hobby servos you can often upgrade the electronics using openservo, or if you have lots of money you can damage your wealth and go for dynamixel servos.

:::ROBOTIS::: (http://www.robotis.com/xe/dynamixel_en)

[edgas10]

thanks , yes i understand how the motors work, but i´m a newbie in robotics.
i´ve made a cnc machine
if i go with the servos is there any board that is simply to connect and can store the positions?
my ideaa is to have a box with a joystick or two to control the movement of the motors, and a pot to control the speed of motors.
thansk

[edgas10]

i´m just concerned because i think servos are not very robust.
thats why i´ve choose the dc motors the thing is that these motors cant find a position, and cannot be controled with a potenciometer for direccion.

[Fivetide]

Just a thought if you want to use a small compact computer for the software you could use a Raspberry PI with a wireless dongle.. just a thought

[edgas10]

would this board be suitable for my needs?

16 Channels Servo Steering gear USB Controller driver board for Robot MCU | eBay (http://www.ebay.co.uk/itm/16-Channels-Servo-Steering-gear-USB-Controller-driver-board-for-Robot-MCU-/261173407565?pt=UK_ToysGames_RadioControlled_JN&hash=item3ccf25ef4d)

[edgas10]

or this?
DFRobot - Romeo Robotic Arduino Board w/ 2ch DC Motor C | eBay (http://www.ebay.co.uk/itm/DFRobot-Romeo-Robotic-Arduino-Board-w-2ch-DC-Motor-C-/130823639883?pt=UK_Computing_Other_Computing_Netwo rking&hash=item1e75b2534b)

[D.C.]

if i go with the servos is there any board that is simply to connect and can store the positions?
my ideaa is to have a box with a joystick or two to control the movement of the motors, and a pot to control the speed of motors.
thansk


i´m just concerned because i think servos are not very robust.
thats why i´ve choose the dc motors the thing is that these motors cant find a position, and cannot be controled with a potenciometer for direccion.

I'll say it again as you seem to have missed it, a servo IS A DC MOTOR (usually)(with a gearbox, encoder and electronics). You seem to have a mental block processing that fact. There are many thousands of different types of servo to suit all uses and budgets, if you are looking at for example a 9g mini servo made of plastic with cheap plastic gears you would be correct to say it is probably too weak for you. But if you are looking at a high end robotics dynamixel servo made from titanium it is rather a lot of overkill.

Until you can say what forces you want your robot arm to deal with you can't really pick the right motors, until you have chosen the motors and figured out what their power requirements are you can't choose a control board/driver/chip because a 3 amp draw on 300mA chip will not work just like it's daft to buy a 70V - 15A board for a servo that wants 1A at 12V.

If you want something that just works out of the box with all the work done for you, you need to buy a robot arm kit.

Lynxmotion - AL5D Robotic Arm Combo Kit (BotBoarduino) (http://www.lynxmotion.com/p-868-al5d-robotic-arm-combo-kit-botboarduino.aspx)

Don't forget you also need a way to save positions, delete positions, name positions, select positions, a way to instruct the robot arm to move to the correct position etc etc. You will need a lot more than just two joysticks to get the functionality that you desire.

[edgas10]

ok lets say that i use the mg996 servos, they can handle 11kg so its good enough for me.
the arm of the robot will have 20 cm in the first and 20 on second section (starting from base)
the box to control i was thinking on using pots to control it .
to store the position i can draw a scale around the pots this way i can write them on paper and them when i need it just put the pots in the right place

[D.C.]

ok lets say that i use the mg996 servos, they can handle 11kg so its good enough for me.
the arm of the robot will have 20 cm in the first and 20 on second section (starting from base)

How do you know that is good enough for you?
Have you actually worked it out?
How much does everything weigh?

The 11kg is 11kg-cm - That means when supplied with 6V it can move an absolute maximum weight of 11kg that is attached to a point 1cm from the centre. You are proposing to stick a microphone, a microphone holder, a load of aluminium, connectors and several servos at a distance of 40cm, I seriously doubt an 11kg-cm servo will handle that load...

If you examine the previous link I sent you as an example, a different sized servo is used for every joint, because each joint in the chain needs to be stronger than the last to move the additional weight. You can't just throw together a random bunch stuff and hope it all works, that is fine if you are learning how to do things but will just end in failure and disappointment if you are trying to deliver an actual useful product.

PS I'm getting a bit confused as you keep drip feeding in various bits of information.

Are you trying to make a 'robot arm' like this:
Home Made Robot arm picks up coin - YouTube (http://www.youtube.com/watch?v=pm1hNNK8yOw)
Home Made Robot arm picks up coin - YouTube (http://www.youtube.com/watch?v=pm1hNNK8yOw)

Or do you actually want a 'motorised microphone' like these:
Mic robot prototype - YouTube (http://www.youtube.com/watch?v=peuNEIw3maw)
Richard Z. Kruspe on the Rammfire amp emulation - YouTube (http://youtu.be/ApLHCbQ3gnw?t=2m29s)
Robot Mic Stand - YouTube (http://www.youtube.com/watch?v=yIk2ubrCRpI&feature=plcp)

[Fivetide]

Personally hardware is the easy thing to workout - the hard part is finding a program that will make everything move at the right speed and stop when you want it to.

[Jonathan]

There's a very good selection of hobby servos at Radio Control Planes, Helicopters, Cars, Boats, FPV and Quadcopters - Hobbyking (http://www.hobbyking.com) should you decide to use that type of motor.


the hard part is finding a program that will make everything move at the right speed and stop when you want it to.

That's when you write your own.

[D.C.]

Personally hardware is the easy thing to workout - the hard part is finding a program that will make everything move at the right speed and stop when you want it to.

I find software loads easier than hardware, you just have to remember how incredibly stupid a computer really is, it will do exactly what you tell it to do, no more, no less.

[edgas10]

How do you know that is good enough for you?
Have you actually worked it out?
How much does everything weigh?

The 11kg is 11kg-cm - That means when supplied with 6V it can move an absolute maximum weight of 11kg that is attached to a point 1cm from the centre. You are proposing to stick a microphone, a microphone holder, a load of aluminium, connectors and several servos at a distance of 40cm, I seriously doubt an 11kg-cm servo will handle that load...

If you examine the previous link I sent you as an example, a different sized servo is used for every joint, because each joint in the chain needs to be stronger than the last to move the additional weight. You can't just throw together a random bunch stuff and hope it all works, that is fine if you are learning how to do things but will just end in failure and disappointment if you are trying to deliver an actual useful product.

PS I'm getting a bit confused as you keep drip feeding in various bits of information.

Are you trying to make a 'robot arm' like this:
Home Made Robot arm picks up coin - YouTube (http://www.youtube.com/watch?v=pm1hNNK8yOw)
Home Made Robot arm picks up coin - YouTube (http://www.youtube.com/watch?v=pm1hNNK8yOw)

Or do you actually want a 'motorised microphone' like these:
Mic robot prototype - YouTube (http://www.youtube.com/watch?v=peuNEIw3maw)
Richard Z. Kruspe on the Rammfire amp emulation - YouTube (http://youtu.be/ApLHCbQ3gnw?t=2m29s)
Robot Mic Stand - YouTube (http://www.youtube.com/watch?v=yIk2ubrCRpI&feature=plcp)

yes you´r right...
i´m sorry that i am changing my ideas every time , but my inicial idead was with steppers.
when you said that it could be done with servos i started to think diferent.
i want to make a robot arm to do the job of that motorised mic stand you show in the video.
but the person who wants the motorised mic needs 5 axis , so i think i´ts easy to make a robot arm.

[D.C.]

but the person who wants the motorised mic needs 5 axis , so i think i´ts easy to make a robot arm.

Try reading this:

How to Build a Robot Tutorial - Society of Robots (http://www.societyofrobots.com/robot_arm_tutorial.shtml)

Pay special attention to the very first sentence -

"About this Robot Arm Tutorial
The robot arm is probably the most mathematically complex robot you could ever build."

If someone has asked you to build a motorised mic and they are intending to pay you for that, why not build a motorised mic? If all you need is a motorised mic that moves around in front of a speaker you can do this by pulling apart a few old printers and reusing the bits. If you really, really want to use a robot arm why not buy one and use that?

Trying to design a 5dof from scratch that will be good enough for use in a very highly demanding production environment on your first attempt seems a little..... ambitious.

[edgas10]

hi there again, after reading i found that its more complicated than what i thought...
i´m gonna try to do a basic arm with no complex electronics, no store positions etc...
can you please tell me if you can find in this site a joystick that can move 2 geared motors both forward and backwards with just simple wiring?

Transfer Multisort Elektronik - On-line Catalogue | Over 100 000 products offered. (http://www.tme.eu/en/katalog/#id_category=100493&page=1&s_field=artykul&s_order=ASC)