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Author Topic: Recommend me a DC Motor :)  (Read 525 times)
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Ey guys, new to these forums and the Arduino platform.

Need some advice and most likely help down the track.   For one of my uni design subjects we have been enrolled into the Warman2010 comp and we need to create two devices, one electrical and one mechanical to pass a container over a 20cm crevice and a minimum of a 40cm height difference.  (Low platform to High)



Decided to use Arduino for the micro controller on the electrical device.  

Stupid questions but I'm wondering what DC motors "rpm" are usually more than sufficient to move a small device say 35cm x 35cm x 20cm (l,w,h) up to 6kg in weight.   I'm thinking 4 motors, one for each wheel or jsut the back two.  Open to any input and ideas

Looking at these things haha
First is, 10:1, 3000rpm
http://toysdownunder.com/arduino/robotics/motors-gearboxes/10-1-gearmotor-high-power.html
Second is, 10:1, 1300rpm
http://toysdownunder.com/arduino/robotics/motors-gearboxes/10-1-gearmotor.html
Third is, 50:1, 250rpm
http://toysdownunder.com/arduino/robotics/motors-gearboxes/50-1-gearmotor.html

Open to recommendations, hoping someone has played around with these motors or similar smiley and can tell me what i should be looking for

If someone can also point me in the right direction for tutorials on programming servo's, dc motors, speed control etc and even, useful circuits like "H bridges" or anything.  Much appreciated.  Searched the web but i dunno how reliable everything is.  (Hoping for something in a bit more depth than what i found under learning unless that's as complicated as it gets smiley)

Cheers Trent
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Trent, can you give us a better feel for your design? It's hard to suggest a motor without knowing exactly HOW you are trying to move the 6kg object over that crevice. Catapult? Wheeled vehicle? Biped? Hovercraft?
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Okay

On the lower surface we will have the mechanical device, which will be a controlled Catapult which will throw the load onto the upper surface into device two. (the electrical one)

Thus we need some motors to drive a device  like theirs in the linked video below to move the load about without much of a hastle


Cheers Trent


**Edit**
If its easier i want some motors to drive a remote control car weighing, 6kg
« Last Edit: July 29, 2010, 08:50:59 am by trenthan » Logged

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So you're at uni and you have a design project to complete

Isn't what you are asking not "cribbing"

When I was at uni we had to do our own reading and research to ensure we understood what we were working with

I think they called it "learning"

Much as we like to help, I think we would not do you any favours if we provide solutions that, with effort, you can solve yourself.

jack
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Unfortunately I'm a mechanical engineer and I've never taken an electrical subject besides basic circuit analysis smiley-sad.  Thankfully I came through a trade school and did quite a bit of electronics so I've got a decent understanding. (of the basic's).  You ask my course peers what's a transistor they haven't a clue.

We ask the lecturer's are we going to learn anything about electronics', IC controllers, motors.  No it's a “mechanical design subject” gotta laugh since the 2nd device has to be electrical.  Its our first design subject, never made anything before since the uni primarily focus's on the theory not the practical side.

What makes it worse, is we already pay for our course than the uni says by the way you have to fund this too yourselves; which is quite harsh when you gotta buy books, software, take a loan for yea course.  Its the way the cookie crumbles unfortunetly

The electrical books ive basically been through are all circuit analysis, rms feeds, micro controllers, mosfets, NOS transistors, Resonant circuit, load line analysis, Zener diodes etc all don't help with this.  Im not asking for a design at all, our group has got one just simply what would drive the device.

From what I've read I'm under the understanding its harder to control a higher “RPM” motor due to the lower internal resistance.  Thus if we stop the current running through the motor it still rolls on due to momentum.  A lower torque motor, doesn't have as much momentum and wont move as far when we cut the current to it.  Problem with this type of motor from my understanding is it cannot move a device with a high weight.

 I'm just simply trying to cut down buying and trying technique since we have spent enough already and everything has to be mail order with shipping fees smiley-sad (the electronics stuff basically)  If you can point me in the right direction of where to look since “we our group” hasn't had much luck.  

Cheers Trent
When u say "cribbing" jack im assuming you mean cheating??? (We ask people in the field quite abit and its not stealing idea's thats research smiley )
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Google is pretty good for research, you'd be surprised at what your competition is prepared to divulge.

Personally I'd look to your project management strategy and have you and your group come to a concensus about your final designs.  That way at least you're presenting folks with "this is what we ARE doing... just a bit stuck on XXXX part of the programming".

What you are asking is that folks give you the answer.  That's not research, it's cheating, no matter how you dress it up.

If memory serves from my own mechanical engineering studies, torque / mass and energy were all part of mechanics too.  Time to use the grey matter dude  smiley-wink
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Quote
From what I've read I'm under the understanding its harder to control a higher “RPM” motor due to the lower internal resistance.  Thus if we stop the current running through the motor it still rolls on due to momentum.  A lower torque motor, doesn't have as much momentum and wont move as far when we cut the current to it.  Problem with this type of motor from my understanding is it cannot move a device with a high weight.
Torque and RPM are not the same thing. Not by a long shot.

Doing the research needed to select a motor yourself will be very valuable, in the long run.

Also, keep in mind that it is not just the motor you need to be concerned with. You need to power the motor, so batteries or other power supply will be needed. The torque can be multiplied or divided, and the speed reduced or increased, if you use a gear drive or pulleys and a drive belt.

Every motor manufacturer has information on their website that will help you choose an appropriate motor. Look at some.

As Funky Diver has pointed out, past competitors like to (or have to) document their designs. Look at what worked for them and what didn't. Studying the losers is as important as studying the winners.

If you come here and ask will this specific motor (with link) do such-and-such, we'll be willing to answer. If you ask is this motor better than that motor, we'll answer (if we know and if we know the criteria for deciding which is better).
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Indeed they are; "torque / mass and energy", used it all when determining the mechanical one.  Centre of mass was the best bit for a 5kg weight lolz since it swings it up and dumps in over the crevice and onto the top side, without the device tipping since the transfer of mass is done quickly.  Mechanical device is built, just the electrical one.  Design has been done, just cant go further till we worked out what motors and their physical dimensions of them are.

With what u said RPM, and torque we did calculate it and got lol, 60rpm and a torque of about 550 to drive it at least.  Only problem with these motors is the RPMs are so high.  Never worked with them and from what I've read in “general” there is a trade off between RPM and stopping precision unless you spend a fortune.  Due to the armature/windings resistance.

All good now anyways.  Broke the old remote control car and had a play around with some older variable resistors back from the day.  Few resistors and it looks like we are fine.  High torque motor it is and slow it down with resistors. smiley by controlling the current.  Worst case was a custom made gear box, cost a fortune and weighs too much for our liking by the time you add 1 for each motor.

Btw, Arduino board was pretty good; wasn't too bad to program actually.  Haven't hooked it up and tried it as a complete system, but testing the code and sensors attached it all seems to work.  Let you know how it goes

Thanks; & Peace. smiley
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