Controlling 2 4amp 12vdc with the Adafruit Motor Shield

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bhtp
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by bhtp »

Alright, Thanks.

bhtp
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by bhtp »

64 jumpers cut and stripped later I have finished wiring the first motor and am now going to modify the code.

bhtp
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by bhtp »

So I have modified my program and have tested it with my Motor Shield, strangely enough when hooked up to my 14v drill battery I receive only 2.5 v at 0.5 amps from the motor shield. As I mentioned before I am very new to the motor shield, but how can I get it to output the level of voltage/amperage in the power supply?

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adafruit_support_bill
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by adafruit_support_bill »

64 jumpers cut and stripped later I have finished wiring the first motor
I'll bet that looks impressive!
when hooked up to my 14v drill battery I receive only 2.5 v at 0.5 amps from the motor shield
  • Check all your wiring. Make sure all L293's are wired in parallel pin-for-pin.
    Check that all the jumpers are firmly seated. Breadboards connections are not always reliable.
    Keep your high-current jumpers (supply and motor) short and use heavier wire if possible.
What code are you using to test this? Is it giving full throttle (speed = 255)?

bhtp
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by bhtp »

Alright, so my wiring is looking ok, I'm pretty confident that the amperage is being evenly dispersed because all 4 of the drivers are getting up to about 140 degrees f. The code which I'm using purely for testing purposes is simply applying actions to both motors rather than modifying the library for now:

Code: Select all

#include <AFMotor.h>

AF_DCMotor motor(2, MOTOR12_64KHZ);
AF_DCMotor motor2(1, MOTOR12_64KHZ);// create motor #2, 64KHz pwm

void setup() {
  Serial.begin(9600);           // set up Serial library at 9600 bps
  Serial.println("Motor test!");
  
  motor.setSpeed(225);   
  motor2.setSpeed(225);    // set the speed to 200/255
}

void loop() {
  
  
  motor.run(FORWARD);
 motor2.run(FORWARD); // turn it on going forward
  delay(2000);


  motor.run(RELEASE);  
    motor2.run(RELEASE);  
    delay(10000);
  // stopped
  
} 

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adafruit_support_bill
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by adafruit_support_bill »

Disconnect the outputs of motor 1 and motor 2 and double check the polarities. Make sure that the two channels are not working against each other.

bhtp
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by bhtp »

I've double checked the polarity and it seems good. Reading them individually I get only 2.5v from one and 0.6 v from the other. Is there a setting or will it usually output the voltage/amperage of whatever's plugged into the ext_pwr? I did check the polarity of the battery aswell. I'm sort of stumped.

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adafruit_support_bill
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by adafruit_support_bill »

With the output at full throttle (speed = 255) you should see EXT_PWR minus about 1.2 volts.

raviolidon
 
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Joined: Fri Jun 03, 2011 6:42 pm

Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by raviolidon »

Just wondering if you modified the library? I have the same problem with my application and would be cool to hear your results. So far I changed my chips to the SN754410's and piggybacked them with heat sinks. I have the terminals setup with kickback protection diodes (2 schottky diodes per motor line). I have the code ready for running two 12-24VDC motors simultaneously in each direction (forward and reverse) using switches to control each direction; but I need to draw a current of 3.5amps so I am going to wait until I wire my motors in. Let me know what you have found! Thanks!

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ze.gmonteiro
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by ze.gmonteiro »

Hi, a little time passed, but I'm having a problem like this... I want to control 2 12vdc motors with my motorshield, but each one of them are draining sort of 4amps. I'm a little confused here. To do so I would need 4 l293 in my board, right (one piggyback in each original l293)? And them I would have to wire motor 1&2 together and the same with motor 2&3. To do so it is just to use 4 wires in each motor (2 wires in M1+2 wires in M2 for the first motor and then 2 wires in M3+2 wires in M4 for the second one)? Is that right?

Thanks for the help and sorry for the english!

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adafruit_support_bill
 
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Re: Controlling 2 4amp 12vdc with the Adafruit Motor Shield

Post by adafruit_support_bill »

@ze-gmonteiro - 2 L293D piggybacked will give you just over 1A. Combining two channels will give you a little over 2A. Still not enough to run a 4A motor. In theory, you could try the same configuration, but using SN754410's instead of L293D's for more power. But as noted before. I don't know of anyone who has successfully run a 4A motor with the motor shield yet. For a good selection of higher-powered motor controllers, you might want to check out http://www.pololu.com.

If you do try the combined channel solution with the motor shield, you will need to be very careful in your code to make sure that the two sides of the chip are never working against each other. This means making sure that both channels are stopped before reversing direction.

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