How to choose geared DC ? :]

Thread Starter

aGpLT

Joined Jan 21, 2010
128
Hello everyone, i am doing project robot arm and i used dc geared 2.4V 1A motors and they are to weak. So i am searching for stronger motors and i dont know how to choose properly, could someone help me ? Ask something if you need more detailed information :]
 

Thread Starter

aGpLT

Joined Jan 21, 2010
128
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Thread Starter

aGpLT

Joined Jan 21, 2010
128
So no one can can help me ? ;] sorry for impatience just i need to know in these days. Just i am quite new with motors and really don't have any idea which one to chose.
 

beenthere

Joined Apr 20, 2004
15,819
I see the pix, but the motor has only the function of closing/opening the gripper? Do you have a figure for the torque produced by the current motor, and have an idea of what the desired torque might be?

And do you have a source of surplus motors to be able to obtain a cheap replacement?
 

Thread Starter

aGpLT

Joined Jan 21, 2010
128
I see the pix, but the motor has only the function of closing/opening the gripper? Do you have a figure for the torque produced by the current motor, and have an idea of what the desired torque might be?

And do you have a source of surplus motors to be able to obtain a cheap replacement?
Yeah it's. Hmm about torque i don't have any idea, sorry. What you mean by last question, can't understand, are you asking, do i know where to get cheap motors ? :]
 

Thread Starter

aGpLT

Joined Jan 21, 2010
128
NO, you will need a motor with a gearbox on it to increase the torque output of the motor to be able to move something heavy with it....

similar to something like this rated at 12/24 volts, 2 amps...



B. Morse
Under load (4.2Ncm) speed is 715rpm, current drain is 0.75A @ 13vdc. or
12vdc gearhead motor produces 18kg-cm torque @ 27RPM with only 330ma current drain. 2 amps i think is to much for me i mean for my controller, max current per channel is 2 amp.
 

BMorse

Joined Sep 26, 2009
2,675
It was just an example of what you need to look for in a DC Gear Motor.... there are plenty out there that draw less current... Just because a motor is rated at 2 amps doesn't mean it will always draw 2 amps... it all depends on the load on the motor....

B. Morse
 

BMorse

Joined Sep 26, 2009
2,675
that says the stall current is 2.2 amps, I thought your driver can not handle anything above 2 amps??

And this has been altered to be used as an AC generator..... don't think that would work for your application..notice the 4 leads coming out of the motor??

Barber Colman Geared Motor Generator
P/N CYQM23061-5-2
Motor Specs
Input Tested at: 12 VDC, 650 ma. current
350 RPM @ 7.5 oz-in Torque, Cont. Duty
Our Lab Test 34 oz-in stall torque @ 2.2A
Generator (brushless- AC output) 6V at 1800 RPM
(approx. 3.3 V / 1000 RPM of the motor)
 

Thread Starter

aGpLT

Joined Jan 21, 2010
128
that says the stall current is 2.2 amps, I thought your driver can not handle anything above 2 amps??

And this has been altered to be used as an AC generator..... don't think that would work for your application..notice the 4 leads coming out of the motor??
But as you said it doesn't mean that it will use so much it depends on load. hmm, i thinked that if i only use two wires it will work fine without that generator :]
 

retched

Joined Dec 5, 2009
5,207
How much does the arm weigh? how much do you want it to lift?

You should not have picked a controller until you have chosen what motor to use. And you can't choose the motor until you know how much weight you need to move.
 
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Thread Starter

aGpLT

Joined Jan 21, 2010
128
How much does the arm weigh? how much do you want it to lift?

You should not have picked a controller until you have chosen what motor to use. And you can't choose the motor until you know how much weight you need to move.
am its really light because arm is made from veneer, i think it would be near 1kg without motors on it. that box weight is about 200g which i need to move. < approximately. I can't really say exactly because i can't measure it. These motors which i have now at start worked perfectly i mean without controller it could work normal without problems, but when i made controller and tryed again it couldn't lift hand, dunno why, and now without controller is the same so i think i need more power. But i can't choose correctly because i really don't know which ones are good enough.
 

Bernard

Joined Aug 7, 2008
5,784
Amount of power depends in part on how fast arm needs to move, what lowest angle arm makes with base, pitch of drive screw? Motor looks good to me, might add low value resistor in series with motor for current sensing to avoid stall current. Use AC later for feed back.
 

retched

Joined Dec 5, 2009
5,207
If the motor worked fine before the controller, You don't want that controller.

You should use a PWM control for the motor. That will allow you to use the motor at proper "strength" by using it full voltage and current. The PWM turns the motor on and off VERY VERY fast to change the speed in which it spins. The controller you are using is most likely reducing the voltage to the motor to slow it. That, inturn, is also weakening it.

---- So, you are saying that without the controller, the motor is not too weak. Correct?
--- With the controller, the motor is to weak. Am I right?

Do you have access to a 555 timer chip? or a microcontroller?
 

Thread Starter

aGpLT

Joined Jan 21, 2010
128
Amount of power depends in part on how fast arm needs to move, what lowest angle arm makes with base, pitch of drive screw? Motor looks good to me, might add low value resistor in series with motor for current sensing to avoid stall current. Use AC later for feed back.
For me speed is not main aspect, i need just to move it :]

1. about this angle you are talking ? http://www.ipix.lt/images/28162567.jpg
2. AC generator for feed back, have any link, i searched but can't find :]

If the motor worked fine before the controller, You don't want that controller.

You should use a PWM control for the motor. That will allow you to use the motor at proper "strength" by using it full voltage and current. The PWM turns the motor on and off VERY VERY fast to change the speed in which it spins. The controller you are using is most likely reducing the voltage to the motor to slow it. That, inturn, is also weakening it.

---- So, you are saying that without the controller, the motor is not too weak. Correct?
--- With the controller, the motor is to weak. Am I right?

Do you have access to a 555 timer chip? or a microcontroller?
Yeah i heard about PWM but never tryed it. My controller is L298 it have voltage drop ~1.8-3.2V supply of controller is 5V my motors are 2.4V.

1. Yeah at first without controller it worked perfectly. (used 5V for motors directly)
2. With controller motors don't have enough power.
3. when i tryed another time the same as 1. it didn't worked. so that's why i am searching for new motors.
4. I have microcontroller PIC16F88 i will be using it to control arm.
 

retched

Joined Dec 5, 2009
5,207
The PIC16F88 has built in PWM. You can use that for the motor control.

What you may want to consider, is stepper motors. Stepper motors can be moved one "step" at at time, giving you greater control over your movements. You can also "micro-step" the motors to get even more control over your arm.

They are rated in holding-strength. That is how much weight they can hold still.
 
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