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16  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 05:46:09 pm
[quote author=husein06
My professor keeps stating "You do not have enough torque. Use a motor operated fan to cool the motor driver"

Don't you think you might ought to listen to him?  I also told you that it wouldn't take much to overheat that controller.  One important thing you need to take into consideration is derating your parts as temperatures go up.  Those specs you gave are likely for the controller when it is at 25C.  
I just cant grasp how a fan over my motor driver will help my robot drive? will a fan really cool off the warming of current that much?
and I'm just trying to learn and ask here dont fight me lol
17  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 04:10:56 pm
Try this, pick the robot up and run the motors. Then using your finger try to slowly apply pressure to the wheel and see how much pressure it takes to stop it. Do you or can you post a schematic of your design? It is possible that your motors are not getting enough current, so you will need another or better battery.
http://www.robotshop.com/bat-04-7-2v-ni-mh-rechargeable-battery.html
Im using that battery, 7.2V / 2800 mAH Ni-MH Rechargeable Battery , its fully charged for the motors.

For my entire circuit and arduino I'm using a 9 volt battery, (I gotta find a replacement for that, its running out every 10 minutes)

My professor keeps stating "You do not have enough torque. Use a motor operated fan to cool the motor driver"
18  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 03:40:14 pm
My guess would be the mass of the chassis. And the fact that your on carpet doesn't help either.

The weight of the whole robot is 5.7 pounds, each motor weighs 1 pound, so the chassis is 3.7 pounds very light material.

The motors are supposedly powerful, I thought they will handle something like this.

Is the weight appropriate? maybe the chassis is too long?
19  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 03:26:57 pm
You should add a small delay in there to see the change. Also for that particular segment, I would swap analogWrite(PWML, speed), with analogWrite(PWML, i);//

I just tried it, worked in the Air, again put it on the carpet and it stalled.

Attached are the pictures of my bot. Did I install the motors the wrong way? Should the motor and bracket be above the chassis?

WHY THE STALL! lol its getting frustrating
20  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 03:05:50 pm
Yes the code may works perfectl, but it seems to run the motors at 255 which is full speed. When you try to get the wheels to move the robot at full speed immediately, it stalls. But if you do an analogWrite(pin, 10) followed by a short delay and an analogWrite(pin, 20) etc etc it might start moving.

But instead of hard-coding the 10 and 20 etc into a zillion analogWrites, you would increment a variable called speed and have analogWrite(pin, speed) to get it up to speed gradually.

Code:
int speeds=0;
int speedstep=10;
if ( 127 > turn ){
   drive_Left();
   for (i=0; i < 255; i++)
   {
   speeds=speeds+speedstep;
  analogWrite(PWML, speeds);// speed control
  }
  }

correct?
21  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 02:33:04 pm
Yes the code may works perfectl, but it seems to run the motors at 255 which is full speed. When you try to get the wheels to move the robot at full speed immediately, it stalls. But if you do an analogWrite(pin, 10) followed by a short delay and an analogWrite(pin, 20) etc etc it might start moving.

But instead of hard-coding the 10 and 20 etc into a zillion analogWrites, you would increment a variable called speed and have analogWrite(pin, speed) to get it up to speed gradually.

Thanks for the help, I'm going to try it now, I understood the concept but where would I increment "speed"? in what part of my code would i place it I'm just confused there?

also, my professor stated "The problem is too much load. If it works fine with the wheels off the ground the you know what the problem is.  adding a fan will help. " what do you think?
22  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 02:20:42 pm
Looks to me that you're blasting it straight to full speed immediately? (You need to post more of the code)

It might be worthwhile to have a speedstep of say 10 and a speed of 0, then loop through a section of code that sets speed = speed + speedstep and pwms it the new value of speed, and do the loop until the speed is the value you want.
I don't understand how would i include that?. My issue is, the code works perfectly, as long as the car isn't on the ground.  I can hold it up in the air, and the drive motor does what it is supposed to, and the turn motor works when it is supposed to.  But when I put it down, it works on a nice flat surface for a few seconds.  It wont move at all on carpet.

Code:
 if (errorSum < 25)
  {
    drive_stop();
  }
  else {
  if ( Stotal> 2100 )
  {
  drive_stop();
  }
  else {
  if ( turn == 128 ){
  drive_forward();  
  analogWrite(PWMR, 255);// speed control
  analogWrite(PWML, 255);// speed control
  }

  if ( turn > 129 ){
  drive_right();
  analogWrite(PWMR, 255);// speed control
   }
   if ( 127 > turn ){
   drive_Left();
  analogWrite(PWML, 255);// speed control
   }
 }
  }
//delay(100);
}

void drive_forward()
     {
  digitalWrite(RFWD,HIGH);// right wheel foward h-bridge
  digitalWrite(RRVS,LOW);
  digitalWrite(LFWD,HIGH);//left wheel foward h-bridge
  digitalWrite(LRVS,LOW);
  return;
     }
    
void drive_Left()
     {
  digitalWrite(RFWD,HIGH);// right wheel foward h-bridge
  digitalWrite(RRVS,LOW);
  digitalWrite(LFWD,LOW);//left wheel foward h-bridge
  digitalWrite(LRVS,HIGH);
  return;
     }
    
void drive_right()
     {
  digitalWrite(RFWD,LOW);// right wheel foward h-bridge
  digitalWrite(RRVS,HIGH);
  digitalWrite(LFWD,HIGH);//left wheel foward h-bridge
  digitalWrite(LRVS,LOW);
  return;
     }
    
void drive_stop()
     {
  digitalWrite(RFWD,LOW);// right wheel foward h-bridge
  digitalWrite(RRVS,LOW);
  digitalWrite(LFWD,LOW);//left wheel foward h-bridge
  digitalWrite(LRVS,LOW);
  return;
     }
23  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 02:01:35 pm
I mean are you sending just one PWM value to set it to 155, or are you looping through a pwm command and increasing the value from 0 to 155 in steps of say 10.



This is how I'm doing it.

Code:
if ( turn == 128 ){
  drive_forward(); 
  analogWrite(PWMR, 255);// speed control
  analogWrite(PWML, 255);// speed control
  }
void drive_forward()
     {
  digitalWrite(RFWD,HIGH);// right wheel foward h-bridge
  digitalWrite(RRVS,LOW);
  digitalWrite(LFWD,HIGH);//left wheel foward h-bridge
  digitalWrite(LRVS,LOW);
  return;
     }
24  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 01:35:33 pm
Are you accelerating the motors gradually from standstill? Those look to me like large wheels to run without gearing.... (without doing any calculations that is.)

Would accelerating be considered doing PWM?
not sure what you mean by accelerating. I'm using an Arduino and just sending a PWM signal.
25  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 01:25:30 pm
The stall current of the motors is such that they would overheat the controller pretty fast, but I assume that you aren't just turning them on at 100% duty cycle from a stand-still, are you?  What PWM frequency are you using, 10kHz is pretty high.  Depending upon your motors, they might have too much inductance to actually draw much power at that frequency.

I'm not sure what you mean, I'm using the arduino PWM 155/255 so .58 duty ratio.
26  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 01:23:03 pm
The stall current of the motors is such that they would overheat the controller pretty fast, but I assume that you aren't just turning them on at 100% duty cycle from a stand-still, are you?  What PWM frequency are you using, 10kHz is pretty high.  Depending upon your motors, they might have too much inductance to actually draw much power at that frequency.
Your motors probably dont have enough torque, in which case you will some kind of gear system.
It might be a simple mechanical problem to do with (lack of) gearing.

Have you got a motor driver chip in the mix somewhere though?- if you have say a 298 in there you'll be losing volts at the best of times but even more if the current is high with a motor trying to get the robot started. What's the voltage at the motors?

I'm using these motors,
http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/587/Default.aspx?txtSearch=motor+wheel+kit
and this motor driver
http://www.pololu.com/catalog/product/1213
27  Using Arduino / Project Guidance / Re: Autonomous Robot, motor driver on: February 22, 2013, 12:15:55 pm
What you using to power it on the ground?
Using a 7.2V rechargeable Battery for the motors, and arduino 9v and laptop cord for the rest of the project, but the main problem is the motors spin perfectly when not on the ground.
28  Using Arduino / Project Guidance / Autonomous Robot, motor driver on: February 22, 2013, 11:42:08 am
Hello all,

So, long story short, I made an autonomous robot.

2 Problems: Wont drive when put on the ground and everything shuts down when not using CPU power.

My robot works perfectly when not put on any surface, the wheels are spinning very well, then the first time I tried it on a surface it worked for 10 seconds only, then after that every-time I put the robot on any floor surface it can't drive, then I lift it it works fine, and so on. My robot all together only weighs 4lbs.
Using a 7.2V rechargeable Battery
Motors: Motor Ratings (at 7.2 VDC):
No-load Current: 0.27 A @ 310 RPM
Stall Current: 4.8 A
Max Torque: 4.6 lb-inch (5.3 kg-cm)

Motor Driver:
Operating voltage: 5-28 V
Maximum PWM frequency: 10 kHz
Current sense: 0.59 V/A
Time to overheat at 5 A*: 2 s
Time to overheat at 4 A*: 21 s
Time to overheat at 3 A*: 165 s
Current for infinite run time*: 2.5 A

What seems to be the problem, wrong motor driver, motors too weak?
29  Using Arduino / Project Guidance / Re: Robot Chassis on: February 05, 2013, 07:10:46 pm
To hold 10 pounds you don't need a 2x4 Chassis. It will add unnecessary weight to the thing an deplete your batteries faster when moving.
Alluminum will be ideal; but probably too expensive. Simple 1/2"x 2''  or 3/4"x2" boards will probably work fine for the frame at a fraction of the weight and cost. You can just reinforce the corner joints with triangular pieces of plywood.

The dimensions are not for the weight itself, it's more for what I'm trying to put on there. So you're suggesting aluminum, won't that be bad incase of a grounded wire or something static??
30  Using Arduino / Project Guidance / Robot Chassis on: February 05, 2013, 06:37:08 pm
I'm building a Robot that holds up to 10 pounds and has 2 power motors and a 3rd wheel (caster) in the back.
Desired Chassis 2 1/2 feet by 1 1/2 feet.

So my question is, what's the best material for a chassis, 2x4 axle with plywood on top? plexiglass?

any suggestions?
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