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Topic: Looking for a motor shield... (Read 4334 times) previous topic - next topic

rloehner

Hi, I am looking for a motor shield that I will use to power 4 DC bidirectional motors. I need something that is cheap and easy to use, but can handle 4 12V DC motors. It would be best if you could get back to me ASAP. Suggestions?

Thanks

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

raschemmel

I would have suggested the DK Electronics Motor Shield (Adafruit Motor shield) but I didn't want to do that until the OP answered that question.

rloehner

Thanks for responding so quick, but i so not know the stall current of hand. We had just found a bunch of parts and motors in the back room and are going to make a robotic arm with it. It does not say the stall current, or even the brand name, on the motor itself so i will have to look up the serial number for it and find out.

rloehner

Alright, 2 of the motors stall currents are at 132.9 A, another is at 4 A and the last motor is an actuator, but I do not have it at hand so i don't know.

raschemmel

#5
Apr 02, 2014, 11:19 pm Last Edit: Apr 02, 2014, 11:23 pm by raschemmel Reason: 1
Quote
Stall current is the maximum current drawn1, when the motor is applying its maximum torque, either because it is being prevented from moving entirely or because it can no longer accelerate given the load it is under.  


Quote
Hi, I am looking for a motor shield that I will use to power 4 DC bidirectional motors. I need something that is cheap and easy to use, but can handle 4 12V DC motors. It would be best if you could get back to me ASAP. Suggestions?


Quote
Alright, 2 of the motors stall currents are at 132.9 A, another is at 4 A and the last motor is an actuator, but I do not have it at hand so i don't know.


I sorta doubt you're going to find a motor "shield" that can handle a 1500W (130A*12V=1560W) motor.
I found this on ebay:
http://www.ebay.com/itm/DC-Motor-Speed-Control-Controller-12V-100A-Reversible-/160976167945
You can look here for the other motors :
  http://www.thefind.com/family/info-pwm-motor-controller

rloehner

Thank you for your help, I am new to electronics and your help is greatly appreciated. Are you talking about max power being at 1500W, because the data sheet i am looking at says 337W. If I am incorrect, do you think i am going overkill using those motors to move a robotic arm?

raschemmel

Let me see if I understand this correctly . You posted for help on the forum , asking technical questions about hardware you have and DIDN'T BOTHER TO POST THE DATASHEET !? !!!  Are we PSYCHIC ? Come on! Post the datasheet for crying out loud and THEN ask your questions.

rloehner

Oops, that was my bad. Meant to put it up in my last post, i found it after researching for the  stall current. The 2 big motors are the pm25r-44f-1005, i think it is the fourth from the bottom on the sheet

Link: http://penfieldrobotics.com/wiki/images/7/7f/2013_Motor_Data_Table.xls

raschemmel

#9
Apr 03, 2014, 12:58 am Last Edit: Apr 03, 2014, 01:17 am by raschemmel Reason: 1
I modified your table with a calculation for the operating current:
OHM'S LAW (The penalty for FORGETTING OHMS LAW is  PIE in the EIR !)

P (Power in Watts) = I (Current in Amps) x E ( Voltage in Volts)= 337W = (I x 12V)=>  I = 337W/12V=28.08A

CONCLUSION ? : YOU NEED A 30A MOTOR DRIVER.
http://www.cytron.com.my/viewProduct.php?pcode=MDS40A&name=SmartDrive40  
This is a top of the line bidirectional uC controller compatible  interface  dc motor controller rated for 40A continuous.
Almost anything else you find will be a step down from this. Here's another good one.
 http://www.robotshop.com/en/cytron-single-7--25v-40a-brushed-dc-motor-controller.html
You have to be careful ordering a motor controller online . Keep in mind, uC users are a minority. Most of the people don't want a uC interface (DIR/PWM inputs) . They want a potentiometer so you have to make sure you don't buy anything until you have seen a closeup photo of the PCB showing the DIR & PWM input silkscreening on the PCB or a datasheet that indicates it has those, otherwise you are going to wind up with a controller that only has the potentiometer control.
The ones I linked above have the uC inputs visable in the photos and diagrams.
Here's one that's less than $50
http://www.robotshop.com/en/30a-5-25v-single-brushed-dc-motor-driver.html
(save the photo and then open it and zoom in on the white 3-pin Molex male connector and you will see the pin labels are
GND
PWM
DIR

rloehner

Thank you so much for helping me out. Since i will be controlling 4 motors, 2 of those big ones and 2 smaller ones, it seems like it will cost a little more than i wanted. Would it be possible to use a relay shield and then control the motors by turning on and off relays through user input on my pc?

raschemmel

Not a good idea. That much current will result in significant arcing inside the relay and could even start a fire.
If I were you I would buy this one . IT'S A DUAL 30A DRIVER ! (and it has the DIR/PWM inputs !)
http://www.aliexpress.com/store/product/Free-shipping-New-0-24V-Dual-30A-H-Bridge-DC-Motor-Driver-Peak-60A-for-Robot/710410_634914339.html 

LOOK AT THE PRICE !
That's a giveaway !  A single is worth $30. This is a DUAL for $32.

rloehner

Awesome, thats a great price! My only concern is, that would cover the 2 big motors, how would i connect the 2 smaller ones?

raschemmel


rloehner


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