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Hello @jwatte

I am a rookie right now in hardware and robotics world and am a student of Computer Science.

Ok i figured out that you would be needing the numbers first
so here is the table of the same below

Robot Dimensions700mm x 700mm x 750mm (l x b x h)
Weight Max.35 kg
Coefficient of friction0.8(Guessed and searched on google need help on this)
Tyres Diameterwill be max 4.5-5.5" (Not decided)
accelerationNeed Help (I am making for war so speed is not that imp but i need acceleration Please suggest )
WeaponTill now only very high dragging and wedged shaped robot design
Max Budget$670(INR 40,000/-)
TradeoffEfficiency is very imp after that its cost then weight is secondary so its 3:2:1

BTW thanks for replying i am trying my best to answer you if i am mistaken or you need More info please feel free to ping me at or firebladevips[at]gmail<dot>com

Mechanics and Construction / Re: Electronic components
« Last post by jwatte on March 28, 2014, 11:45:16 PM »
I keep a shopping cart at Digi-Key. (
Then, every once in a while, I press "check out" and pay the approximately 5-6 dollars of USPS Priority Mail shipping.
Also, I make sure to buy at least 10 of anything cheap-ish (capacitors, switches, etc), and at least 3 of anything big, so that I have spares if they die, and don't have to re-pay shipping for the next project.
For LEDs and resistors and loose transistors, I buy a pack of 50 or 100, and it lasts a while.
Mechanics and Construction / Electronic components
« Last post by 4075aaron on March 28, 2014, 09:53:44 PM »
Where is the best source of buying electronic components (diodes, resistors, capacitors, ect) on line?  I don't want to buy everything from ebay and pay separate shipping for each purchase...
Mechanics and Construction / Re: Actuators for robot arms
« Last post by bdeuell on March 28, 2014, 07:36:19 PM »
There are three common drive methods that come to mind when low backlash is required:

Harmonic drive
Timing belt (in particular the gates GT series belts are supposed to have good performance)
Ball screws

I believe cycloidal drives have low backlash as well but I do not have any experience with them

Springs can also be used to eliminate backlash but I would be concerned about the load range at which they are effective and the impact that would have on your arm.

If you can get sufficient torque without a gear reduction that will eliminate the problem but this is usually challenging in a arm where motor weight is often a concern.

BLDC + Gearhead + Harmonic drive?
If you use gearhead motor that has backlash and then stick a harmonic drive on after ther will still be backlash present however it will be reduced by the gear ratio of the harmonic drive

I believe harmonic drives are quite common in industrial robotic arms.

Robot Videos / Arduino based Tank Bot
« Last post by dayhkr on March 28, 2014, 07:28:37 PM »
Here is the first run of the tank bot.  I still need to tweak the code but it runs.

Qik - tracbot by dayhkr
Mechanics and Construction / Actuators for robot arms
« Last post by Robot Attack on March 28, 2014, 09:01:02 AM »
Hi All,

I am working on developing a new robot arm. It will be roughly .5 meters long, and im shooting for a max payload of ~2kg. 7 DoFs total (Spherical shoulder, elbow, spherical wrist), plus 1 DoF for the end effector itself.

I know that backlash can be a signficant problem in robot arms. I have a pretty healthy budget for this project. My question is, what sort of actuators are generally used in systems like this?

BLDC + Gearhead + Harmonic drive?
Large Stepers, no gearing, resolver to close the loop?
BLDC + Planetary + preload springs?

Anything I am missing in the above options?
What do large industrial robots use?

Misc / Humanoid Robotics Survey
« Last post by codedarm on March 27, 2014, 07:36:32 PM »

I am a college student doing a report on the feasibility of Humanoid Robots being implemented to the public domain. Can you spare just 2 minutes of your time to complete the survey? I would greatly appreciate it. It is opinion based, have at it!

Thanks! :P
Misc / Re: My Robot project
« Last post by gerard on March 26, 2014, 05:17:37 PM »
this is the kind of stuff that will exist in a few decades at least, and requires several billion dollars of funding even for just a single prototype
maybe if you built a working prototype first and displayed it to the public to prove that you are capable of building such a thing, then you might get a few investors?
Misc / Re: Stepper motor driver
« Last post by jwatte on March 26, 2014, 02:59:28 PM »
If you disable the driver, then switch with a relay, then enable the driver, it might work.
I haven't worked with that particular driver, nor those motors, so I have no idea whether it will ACTUALLY work.
But, given those usage requirements you're suggesting, it may be worth a try. The worst that can happen is that you fail, but hopefully in that case, you'd learn something from it :-)
(Often, failures actually are better learning opportunities than successes.)

Your numbers are not sufficient. They only talk about mass, not acceleration or assumed friction.

A tiny, AAA-battery powered motor can move a metric ton of mass if it's suspended on good bearings and you don't need it to accelerate quickly.

So, how much acceleration do you need? 0.1g? 1g? 10g?
What friction coefficient will that mass have towards the ground? 0.0 (lifted in air)? 0.1 (greasy bronze on steel)? 1.0 (iron on iron)?
How much money are you willing to spend? What's the trade-off between efficiency, weight, and cost?
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