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### Topic: Motor power and voltage (Read 3131 times)previous topic - next topic

#### biscottoesse

##### Dec 20, 2014, 06:57 pmLast Edit: Dec 20, 2014, 07:00 pm by biscottoesse
Hi,
I wanna start using 2 motors but I have 3 doubts and would like to hear advice from expert ppl since Im inside Arduino for only 1 week.

My purpose is 2 motors capable of move 15kg so i would like to know:

1.- how can I calculate or see which type of motor/model support that capacity of weight on it.

2.- since the board can only get 5v max, I can't have powerfully motors or I can as long as I put the energy of the motors via another cable, directly to the motors bypassing the arduino board.

3.- I can use 2 motors able to handle 8kg each right, instead of 2 that handle 15? Because even in the turns, I still gonna use both motors (I think this question is really dumb but anyway..)

#### nilton61

#1
##### Dec 20, 2014, 07:28 pm
Motors do not deliver force, they deliver torque. You can convert between them by using a lever or a capstan. So any motor can exert any force. What matters is that the linear power, F(N)*s(m/s) equals the rotational power M(Nm)*rpm/9,55 minus losses. And of course this should equal electrical power U*I minus losses.

#### Robin2

#2
##### Dec 20, 2014, 08:33 pm
2.- since the board can only get 5v max,
What board do you mean?

You should NOT power any motor from the Arduino 5v pin. ALL motors need a separate power supply - even if the motor works at 5v.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### MarkT

#3
##### Dec 21, 2014, 01:57 am
EITHER you are going to have to learn a bit about the branch of maths called "mechanics"
which covers force, velocity, torque, power, momentum, angular-velocity, friction,
moment-of-inertia, OR you'll need to give a lot more detail than "move 15kg"...
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### zoomkat

#4
##### Dec 21, 2014, 04:20 am
Quote
Motors do not deliver force, they deliver torque.
That sounds a bit strange.
Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

#### biscottoesse

#5
##### Dec 21, 2014, 04:22 am
ty for the answers so far.

this is kinda hard ot me since I just have programmer skills and totally new to mechanics and hardware but,
my purpose would be have a motor with a torque able to pull 15kg, more specifically a bucket of water.

#### MarkT

#6
##### Dec 21, 2014, 04:31 am

Dragging a load of 15kg on a horizontal surface?

What kind of surface?  What coefficient of friction can be expected
(easy to measure if a sample of the surface can be inclined - measure the
angle at which the load slides).

How is it dragged?  cord? toothed belt?  Any clues as to the geometry here?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### zoomkat

#7
##### Dec 21, 2014, 04:42 am
Quote
my purpose would be have a motor with a torque able to pull 15kg
You need to factor on the friction it will take to move your load. If your 15kg is sitting on a good skataboard on level smooth pavement, then a linear force of .1 kg might be needed. If the 15kg is mounted on a rubber mat, a linear force of 20kg might be required to make it start moving. If you are lifting the weight, then you would need a motor that would develop more than 15kg-cm while winding a lifting cord being wound on a 2cm diameter shaft.
Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

#### biscottoesse

#8
##### Dec 21, 2014, 05:04 amLast Edit: Dec 21, 2014, 05:05 am by biscottoesse
yes horizontal and wooden surface, without much atrict/friction, just normal floor.
The wheels, just normal rubber wheels, that you find in most robots, the plataform itself gonna be a cube with less than 50cm.

EDIT: its only a plataform that moves forward, backwards, or sides, tranposrting a bucket on top.

#### nilton61

#9
##### Dec 21, 2014, 05:59 am
You need to factor on the friction it will take to move your load. If your 15kg is sitting on a good skataboard on level smooth pavement, then a linear force of .1 kg might be needed. If the 15kg is mounted on a rubber mat, a linear force of 20kg might be required to make it start moving. If you are lifting the weight, then you would need a motor that would develop more than 15kg-cm while winding a lifting cord being wound on a 2cm diameter shaft.

The SI unit for force is Newton (N) or some alternative like lbf or ozf or antiquated units like pond or kp. Never kg which is a unit for mass.

#### Robin2

#10
##### Dec 21, 2014, 10:51 am
yes horizontal and wooden surface, without much atrict/friction, just normal floor.
The wheels, just normal rubber wheels, that you find in most robots, the plataform itself gonna be a cube with less than 50cm.
Do you realize that the second sentence above adds entirely new information. Before that people had been assuming that your 15kg load would be sliding along the surface with all of the friction that that entails.

In your second sentence you tell us that there will be wheels which should reduce the friction enormously.

What else are you not telling us?

You need to make some actual measurements of the force required. Perhaps arrange to pull the platform with a spring balance and note the reading. Then double or treble that value to give yourself a safety margin.

How will the motor cause the platform to move? Will it drive the wheels or will it work as a winch?

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### biscottoesse

#11
##### Dec 21, 2014, 03:09 pmLast Edit: Dec 21, 2014, 03:09 pm by biscottoesse
Do you realize that the second sentence above adds entirely new information. Before that people had been assuming that your 15kg load would be sliding along the surface with all of the friction that that entails.

In your second sentence you tell us that there will be wheels which should reduce the friction enormously.

precisely for this I added that info. and that's all, I just want something 'simple'
a 'simple' squared box with 2 wheels so it can be used like an rc car, but that I can put a bucket on the top, a bucket that weights 15kg max, simple as this, something like:

#### MarkT

#12
##### Dec 21, 2014, 04:17 pm
yes horizontal and wooden surface, without much atrict/friction, just normal floor.
The wheels, just normal rubber wheels, that you find in most robots, the plataform itself gonna be a cube with less than 50cm.

EDIT: its only a plataform that moves forward, backwards, or sides, tranposrting a bucket on top.
You said drag, and now you mention wheels.  They are different methods
of locomtion!

will be at cross-purposes - its more fun for us to solve your problem
than to have to drag information out bit-by-bit from you.  Don't be vague,
be precise.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### Robin2

#13
##### Dec 21, 2014, 05:12 pm
precisely for this I added that info. and that's all,
Why didn't you tell us you planned to use a wheeled platform in your first Post?

Have you tried to measure the required force?

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### MarkT

#14
##### Dec 21, 2014, 05:49 pm
Are you using mechanum wheels then?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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