Robotic Arm using Picaxe

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Vinod

New Member
Hello all,
I am trying to make a robotic arm using PICAXE 28x1. And I have a doubt to ask.! Can PICAXE control 4 geared wheels(yeah the robotic arm is equipped with wheels) and 2 Servo Motors? or should i look for an alternative?
Will be pleased with replies.
 
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westaust55

Moderator
Vinod said:
Hello all,
I am trying to make a robotic arm using PICAXE 28x1. And I have a doubt to ask.! Can PICAXE control 4 geared wheels(yeah the robotic arm is equipped with wheels) and 2 Servo Motors? or should i look for an alternative?
Will be pleased with replies.
Click to expand...
The 28X1 PICAXE can control your robot arm.

Can you provide a link to the datasheet for the robot arm which you seemingly already have?
That will help us to better guide you to assemble/design an interface.

What type of motors are used - simple DC, stepper, other?
What voltage are the motors?
Do you want the motors to operate in both directions?

If the motors are less that 600 mA then using a couple of L293D chips could be used.
 
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Vinod

New Member
I do not have any data sheet.! 4 geared simple DC motors and 2 servo motors and yeah the power consumed is very less and the motors must move back and forth and thus stepper can also be used.! But I need some advice too.!
 
V

Vinod

New Member
And another thing is that I live in India and there is not much of sales as PICAXE is concerned. So can you tell me a place where I can get a good 28x1 board with
 
W

westaust55

Moderator
Vinod said:
I do not have any data sheet.! 4 geared simple DC motors and 2 servo motors and yeah the power consumed is very less and the motors
Click to expand...
Do you have a multimeter multimeter? If there is no datasheet we need to know the currrent draw of the geared DC motors before the type of controller chip can be recommended.
What is the voltage of the power system for the robot arm? What size (AA, C, other) and mAh rating are the batteries.
 
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Vinod

New Member
and is it completely neccessary to use PICAXE programming cable for coding into the arm or shall I use other Cables as well?
 
W

westaust55

Moderator
Vinod said:
AA preferably
Click to expand...
Please try to answer all of the questions . . .

westaust55 said:
Do you have a multimeter multimeter? If there is no datasheet we need to know the currrent draw of the geared DC motors before the type of controller chip can be recommended.
What is the voltage of the power system for the robot arm?
What size (AA, C, other) and mAh rating are the batteries?
Click to expand...
With AA batteries there may be some significant voltage dips when servos and motors start that may acuse the PICAXE controller to reset. There are ways to help circumvent this by having a diode in the supply to the PCAXE and a reservoir electrolytic capacitor of the PICAXE side to help hold the voltage up during motor starting.

Again since you have 4 motor do you want two on one side to run as a pair and two on the other side to run together for steering purposes?
Some more information and at least some photos of the robotic aarm from various angles with help us envisiage what you can already see in front of you (we are in effect working blind).
 
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Vinod

New Member
Yeah Dude..! Thank you for that valuable information. I have still not made the body.! I will be soon doing it. But I can show you an example picture I got from the internet(This is definitely not the exact picture of what we are doing, atleast approximate to cure your blindness).
robot_arm_mobipulator.jpg
It is more or less like this one.! But we might use a hard plastic body with ample weight as the body if we find the metal body too costly.!
I'll just jist out my project in short.!
What I am trying to do is a fully automated robotic arm which has 4 wheels for moving to and fro. I'm equipping it with either an infra red sensor or an ultrasonic range finder that'll be used to find the test object placed some feet away from the robot. After sensing it the robotic arm moves on its own, picks up the test object and if needed will come back to the original position. All are automated. This is the main aim of my project for which I need a lot of help. I loved PICAXE above everything else(be it Arduino pro or RPi(I know it's more sophisticated)) so I resorted to select this as the brain of my project. Yes I might need to make one side of a motor run at a time facilitating turns and steers. PLease help.! THank you.! And I might need a lot of help with coding too(Please guide, I do not ask to give me the complete coding). Thank you.!
 
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Vinod

New Member
I can easily get a multimeter from my college.! How do I calculate the complete power system for my prototype? I intend to use L293D motor driver chip. If you recommend a more sophisticated chip please go ahead and tell.! I have only a little time. My last date for submission is on August 18th(The deadline is a little flexible as my project is a little complicated relatively).
 
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rossko57

Senior Member
Vinod said:
How do I calculate the complete power system for my prototype?
Click to expand...
In the first instance, find out out how much power each of your "consumers" use - motors, lights, servos, PICAXE etc. and add them up. This information is usually available on datasheets. If you have no info on your motors, you might measure the current when operated. Load the motor and it'll go up. It'll be more difficult if you don't even know what voltage the motors are supposed to run at.
Whether the L293D is any use to you depends on the mystery motors.
 
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Vinod

New Member
Lol,yeah.! And I got a multimeter, no worries.! And dude there's no harm in trying anything,is there?
 
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Vinod

New Member
So here are my updates. PICAXE consumes 4.5 V and my DC motor consumes about 12V(No load) and my servo motor consumes 4.8-6v(depending upon seconds/degrees). So totally 4.5+(12*4)+(4.8*3)=66.9V. Thus it consumes around 70V.

P.s: I am a guy with no technical background but with ample of interest. I accept it openly, I do not know a lot of stuffs which you may find utterly ridiculous but I have lots of interest and thus I try whatever I can.! So please do help me for me to complete this project, please do.! Thank you,before hand.
 
JimPerry

JimPerry

Senior Member
Hold on Vinod - your setup "consumes" no voltage - have you ever heard/understood Ohm's Law? :confused:

Voltage=Current x Resistance

Voltage is just a measure of Potential ability to deliver Current through a Resistance - a bit like water pressure. :mad:
 
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Vinod

New Member
I'll do that dude. I'm waiting for my products to arrive. I've ordered those.! And I have some in hand. But as soon as all the products arrive I'll give in the complete details..!


P.S: I'm a little weak in basics, please par with me and do help me to get in the right track.!
 
erco

erco

Senior Member
@Vinod: You haven't mentioned the most important thing yet: feedback. You need to know the angle & position of your arm's linkages. I suggest you start by programming some servos to move in a controlled manner and see how easy or hard that is before you move on to gearmotors and encoders. Just slapping a pile of motors together into something that resembles an arm is looking for a bloody nose IMHO. Numerous examples in the Robotics forum, and/or letsmakerobots.com. Some advance legwork now will help prevent big disappointment later.
 
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Vinod

New Member
Sure man, Thanks for the valuable advice.! :) Surely I will try those.! And get back to you.! And for the feedback, yeah, I need to calculate the position of my arm's linkage and the angle too But, let me first try with the servo coding And I need to calculate.But before that I need to do force calculations before I zero in for my motor, It's forward kinematics(after the angle of linkage is calculated, of course),it's holding capability and it's motion planning. I have to do all that, everything from scratch and I have only a month and a half's time. Heck of a work it is with my zero knowledge base. But interest is what that drives me. Thank you man. Please be there to help me more in this. And do you frankly think that I can pull through this in a month and a half if I do some advance legwork as you recommended?
 
erco

erco

Senior Member
A large, high-capacity finished arm in a month and a half? Very doubtful, based on your experience. Honestly, you would be hard pressed to build a small simple arm using servos. Even those aren't easy. Here are two small arms that I have built:

tiny scratch built arm: http://www.picaxeforum.co.uk/showthread.php?20480-Work-in-Progress-6-DOF-Arm-Uses-PICAXE-20M2

medium sized kit arm: http://www.picaxeforum.co.uk/showthread.php?23025-100-5-Axis-Arm-Kit-incl-Controller

Post #5 in the kit arm thread shows the arm atop a mobile robot base, which IIRC is your ultimate goal. You should definitely consider kits. You'll still learn a lot.

Get crackin'.
 
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boriz

Senior Member
I couldn't build a robot like that without plenty research and plenty money. And I have had a multimeter for >20 years, and a CRO for >15 years.

If I were focused and rich, I could possibly manage it in three months. Possibly.
 
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Vinod

New Member
Thanks everyone, I have been doing much research onto the project now and I m getting into the hardware mode to build everything.. Thanks for getting me to the right path.! I O U all.! One small doubt.! While I was reading my way through PICAXE i came across an information that to initiate the servos, a DIL resistor IC is a must to set up a servo.! Yeah, I know that it is just the array of resistors that block the current.! But is it a must? actually, we dont get resistor IC's in my town.! And my servo operating voltage isnt much low either.! So can I skip it? Thank you.!
 
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russbow

Senior Member
I don't think Vinod is too far off beam.

Manual 3 advises a 330 ohm between picaxe pin and servo signal in.
There also have been many posts on here about the ULN socket on some picaxe boards and some users not realising that the PICAXE output needs to be used.

The suggestion has always been to remove the ULN array and replace with a DIL 330 ohm, available from Rev Ed
 
erco

erco

Senior Member
OK, so the DIL array recommendation is specific to those boards with a ULN2x03 DIP socket. The darlington array is good for switching motors, but not for servo signal throughput. But that's sort of a quick, off the shelf patch to use that board. Aren't those general purpose, cheap insurance, current limiting resistors in case of a short circuit to ground to save IO pins? I have never used them on numerous servo projects, never had any problems. From my experience, no resistor is needed and a direct connection is fine. YMMV. :)
 
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Vinod

New Member
I have a problem running PICAXE.! I have been fondling with PICAXE for a while. But suddenly when I was experimenting with Servos. I changed my USB to COM6 and changed it in the winAXEpad options as well. But when I program something into it, it says Hardware not found on COM6. I am completely vexed. Please solve the problem for me guys. Thank you.! :)
 
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Vinod

New Member
But the peculiarity is that, the firmware is detected in Picaxe programming editor but not in WinAXEpad.! And the coding does not work either.! Please help.!
 
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