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Topic: motor shield r3 gets really hot with 12V dc motor (Read 690 times) previous topic - next topic

Kumalix

Feb 11, 2018, 08:56 pm Last Edit: Feb 11, 2018, 09:06 pm by Kumalix
Hi,

I'm also new to the Arduino community.
So please explain things newbie way  :smiley-confuse:

I have:
1: Arduino uno r3
2: motor shield r3
3: a AC to DC adaptor with these specs:
- Ingangsvoltage: 100 - 230 V AC/50 Hz
- Uitgangsvoltage: 3/4.5/6/7.5/9/12 V DC
- Uitgangsstroom: Max. 2250 mA
- Max. vermogen: 27 W
- Afmetingen: 88x51x42 mm
- pluggen: 2.5 mm, 3.5 mm, 2.1 x 5.0 mm, 2.5 x 5.5 mm, 1.35 x3.5 mm, 1.7 x 4.0 mm, 0.75 x 2.35 mm
4: a 12V DC motor. Of this i don't have the exact specs. but i think is this:
motor 12 v dc

5: The Code; its basic, just to get me started.

void setup() {

//Setup Channel A
pinMode(12, OUTPUT); //Initiates Motor Channel A pin
pinMode(9, OUTPUT); //Initiates Brake Channel A pin

}

void loop(){

//forward @ full speed
digitalWrite(12, HIGH); //Establishes forward direction of Channel A
digitalWrite(9, LOW);   //Disengage the Brake for Channel A
analogWrite(3, 255);   //Spins the motor on Channel A at full speed

delay(3000);

digitalWrite(9, HIGH); //Eengage the Brake for Channel A

delay(1000);

//backward @ half speed
digitalWrite(12, LOW); //Establishes backward direction of Channel A
digitalWrite(9, LOW);   //Disengage the Brake for Channel A
analogWrite(3, 123);   //Spins the motor on Channel A at half speed

delay(3000);

digitalWrite(9, HIGH); //Eengage the Brake for Channel A

delay(1000);

}


Now the problem is that the motor shield (center big chip) gets really hot and i have to turn it of. It begins to smell.

I have done reading a lot on this forum and i think that the motor draws to much amps (current)
is this correct? or? Is there a way to avoid this overheating problem with this shield?

Even if i set the adaptor to output 9V it still gets very hot.

Hope some can help.

tnx




slipstick

That motor might be trying to draw 30A or more. The motor shield can only deliver 2A. That is not a good combination.

The current a motor needs will depend how much load it is under. So what is your motor actually driving?

Steve

Wawa

That motor shield uses an ancient bjt based L298 motor driver chip with a typical drop of 2.5volt@1Amp.
That means a dissipation of 2.5watt with a 1Amp motor.

Your motor seems to draw 1.2Amp unloaded, and has a load and stall current much higher than that.

Glue a heatsink to the chip, and plug and pray. Or get a better (mosfet based) motor driver.
Pololu.com has a good selection.
Leo..

Kumalix

I want to make a actuator my self.
The motor should drive this:https://reprapworld.de/products/linear_motion/tr8x2_leadscrew_8mm_30cm/

Another issue i just came across is that if i hold the motor shaft with 2 fingers and apply a smal smal minimum amount of pressure the motor wont turn at all. it just zooms.
So i do believe that the motor need much much more amps to be able to start with sufficiënt torque.

am i correct?

Wawa

It seems you try to use a high RPM brushed motor for a lead screw that needs a low RPM stepper motor.
No practical experience there (I have a factory made CNC machine).
Leo..

Kumalix

That's true. I'm trying to figure things out and want to make my own Actuator.


I have ordered this motor:
NEMA17

If i'm correct this one should do the trick?
And i can connect him to the arduino motor shield r3? right?

MarkT

No, that needs a stepper driver like a DRV8825
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Kumalix

ok, i have also this driver here with me.

TEPPER_MOTOR_CONTROLLER_MODULE.pdf

can i use this one? or should i just order a beter driver?

tnx for the help! i appreciate it!!

Wawa

Same L298 chip, different package (flat vs. upright)

That breakout board migh run a bit cooler because of the heatsink.

Those chips are really meant for higher voltage, low current motors (e.g. 24volt <1Amp).
The reason you find them in the Arduino market, along with the smaller L293, is because they are cheap.
Technology has advanced a lot since they have been designed (35+ years ago).
Leo..

jremington

#9
Feb 13, 2018, 01:46 am Last Edit: Feb 13, 2018, 01:50 am by jremington
Quote
can i use this one?
No.
Quote
or should i just order a beter driver?
Yes, see reply #6. Pololu.com sells DRV8825 drivers. Be sure to follow directions and set the current limit to 1.5A or less.

Kumalix

Ok tnx. It did work!
 But this L298 driver gets pretty hot i notist.
I had it run a NEMA 23 1 Nm driver back and fort voor about 1 hour.
With 12V 2.2A adaptor. 


Therefor just order 4 of those DRV8825 drivers.  :D
I need to run 2 or 3 Nema stepper motors.

I will wait for the package to come. And read the instuctions.

Quote
Be sure to follow directions and set the current limit to 1.5A or less.
Because i don'f fully understand the above sentense.  :smiley-confuse:

MarkT

ok, i have also this driver here with me.

TEPPER_MOTOR_CONTROLLER_MODULE.pdf

can i use this one? or should i just order a beter driver?

tnx for the help! i appreciate it!!
No, I said you need a stepper driver, not a motor driver, because you always need a current-controlling
stepper driver for low-impedance bipolar stepper motors (these motors are _current_ driven, not voltage driven).
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Kumalix

Ok, i got the dvr8825.. it's really small  :o

Now the question is how much voltage and current do i have to have?

Like i first posted i got this AC to DC adaptor:
- Voltage can be set to: 3/4.5/6/7.5/9/12 V DC
- Current: Max. 2250 mA
- Max. 27 W

and:
This motor
It sais 1.7A.. does that meen for each coil? or for both?

also where do i set the current with the dvr8825? in arduino IDE?

thanks for helping!

MarkT

Google setting the current for the DRV8825, there are resources out there, certainly at pololu.com for one.
The 1.7A is the current you need to set the driver too, there is only one setting.
If you are interested in the details read up about microstepping stepper drivers, for instance the
datasheets for chips like the DRV8825, A4988
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Kumalix

Ok tnx. I have been reading last night for about 8 hours  :smiley-sweat:

I have set the correct current (VREF) with the potantiometer on the dvr8825 to 0.8 Volts.
with the formula: Current Limit = VREF × 2
So that should give 1.6 Amps to each coil?

But now i have the feeling that the torque of the Nema17 motor not that strong is.
I can hold the shaft of the motor with 2 fingers and the motor slips. (i can stop the shaft from spinning with 2 fingers).

Normaly i would say that the motor isn't strong enough. But with de L298 chip i had much more torque and could not stop the shaft with 2 fingers.
The motor did get a little hot??? While with dvr8825 it stays cool.

Is there a reason for this?

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