HELP! L298 DC Motor Driver

[SzeHan]

Hi,

I was constructed a circuit for L298 for a 12v DC Geared Motor by using PIC16F877A microcontroller. My schematic diagram was attached.  I ran my simulation using Proteus and the circuit works.

However when i tested the circuit in real, the DC motor did not rotate. My circuit is constructed as shown in the attachment. Since it wont work then i unplug my DC motor from Pin13&14 of L298 and check for the voltage. When i probe my multimeter on both Pin13&14, it has potential different with +12v (when the code is for CW rotation) and -12v (when the code is for CCW rotation). (For my code i made the motor to rotate CW and CCW). But when i connect DC motor to Pin13&14 of L298, the it only shows constant +12V potential different.

Then i try to connect one of the pin of DC motor to ground, the motor rotate!! IT JUST WONT ROTATE WHEN I CONNECT FOR PINS TO L298!

I wonder why is this happening. Can anyone tell me why it just cant rotate when connected to L298?

Regards,
Sze Harn

[billhowl]

The resistor connected to sens pins R2 & R3 is too high, normally less then 1 ohm.

[Soeren]

Hi,

When current sense/feedback isn't used at all, the pins (1 and 15) should be connected directly to ground.

[SzeHan]

Hi billhowl & Søren,

I tried to connect my Pin 1 and 15 to ground. Then i heard rotating sound coming from the motor but the motor did not rotate. I checked output pin (Pin13 & Pin14) of L298 it shows around 9V (I'm using a 12V motor). At the same time, the voltage of the other output pins of microcontroller drop. Can I increase the output voltage of Pin13&14 to 12?


Regards,
SzeHan

[Soeren]

Hi,

I tried to connect my Pin 1 and 15 to ground. Then i heard rotating sound coming from the motor but the motor did not rotate. I checked output pin (Pin13 & Pin14) of L298 it shows around 9V (I'm using a 12V motor). At the same time, the voltage of the other output pins of microcontroller drop. Can I increase the output voltage of Pin13&14 to 12?

The L298 has a total voltage drop of 2.55V (typ.) at 1A load and 3.7V (typ) at 2A.
The minimum drop possible at 1A is 1.8V
The guaranteed maximum drop at 1A is 3.2V (4.9V at 2A)

That fits fine in the "12V supply and 9V out" (a 3.0V drop) and you could raise the supply voltage at pin 4 to 15V to counter this.

But, I don't think that I have ever seen a 12V motor which wouldn't at least run slowly on 9V, so perhaps there are other issues.
What supply are you using for the 12V and what is its max. current output?
And how much current does the motor require?

[SzeHan]

Hi Søren,

My DC motor works! 
I found out that my power supply is not stable, that is why the motor act weird. Now the output of L298 give around 11V++ and the motor rotate perfectly   
Now I'm trying to do the same for stepper motor. Hope it works.

Thank you for helping me else i will stuck at there for "century".

Regards,
SzeHan

[Soeren]

Hi,

My DC motor works! 

Great

I found out that my power supply is not stable, that is why the motor act weird.

Did you fix it or did you use another supply?

Now I'm trying to do the same for stepper motor. Hope it works.

Of course it will

Thank you for helping me else i will stuck at there for "century".

You're welcome   But I'm sure you would have found out on your own somehow.

[SzeHan]

Hi Søren,

I changed my power supply from unregulated to regulated. Then it works 

Once again, thank you so much.

Regards,
SzeHan