l298 motor driver

[w_bwr]

i 'm using L298 IC to control dc motor, i hav used the schematic which is in the datasheet of the l298. but problem is 8v appears on the motor but it didn't rotate. and when i directly apply 8v to the motor it rotates.

Need help???

[z.s.tar.gz]

First off this should be a sign that 8V is not reaching the motor via the L298. This means that something is not hooked up correctly. Judging by the amount of pins on the chip, I'd say that it is very possible you have a wireing problem.

Let's assume though that 8V is in fact reaching the motors through the chip. This would mean that the motors are unable to recieve enough current (and therefor torque) to start. What kind of motor are you trying to use? The L298 is rated at 3A so it should be enough...

[billhowl]

Please check enable input pins 6 or 11 is high,
Input 1 & 2 pins 5&7 or Input 3 & 4 pins 10&12 are one is high and the other is low. the two Input's are in different level.
The sense A & B pins is connected to ground with 0.5 Ohms resistor or directly connected to ground.
measure voltage across the output to motor (out 1&2 or 3&4 Pins 2&3 or 13&14).

[Soeren]

Hi,

Sound like it's the sense pins that didn't get connected.

[w_bwr]

What do Sense pin do?

[Jak24]

HI  :
I'm using the exactly the same IC driver  this one right: http://www.st.com/stonline/books/pdf/docs/1773.pdf
here are somethings you can check :
the sense pin is the PWM signal generated by the microconntroller but if you whant the motor to run at full speed connect it to 5v
connect one of the inputs to ground other one to 5v and enable also to 5v test it like that if it works then there is something
wrong with your signal
if on side of the h-bridge isn't working check the other side (maybe one side is broken or something)
and check how many amps your motor requires because if it's more than 2A but less then 4A then you can parallel the h-bridge so that both bridges control the same motor
if nothing else works then a take apart the whole circuit and re wire it .... if still you checked all this then it's almost safe to say the h-bridge is broken ...
(and PS : be-careful with it's  pins they tend to break easily  )

Regards

Jak24

[Soeren]

Hi,

the sense pin is the PWM signal generated by the microconntroller but if you whant the motor to run at full speed connect it to 5v

That would not make it work at all!

The sense pin is for connecting a low value resistor to ground. It is the voltage drop developed over this resistor that the L298 uses to limit current.
If the resistor is not used, the pin should be connected to ground to enable the motor to get power and when this pin is open, the positive pole of the motor will show voltage without anything happening, when referenced to ground (as the motor circuit isn't closed towards ground).

Just ground the pins for a quick test, but it may be a good idea to calculate sense resistors for real use, as it will protect the motor from burning out under a locked rotor condition.

[madsci1016]

Hi,

Sound like it's the sense pins that didn't get connected.

I agree with Soeren, to get that h-bridge to work you have to connect the current sense pins to ground.

EDIT: lol, posted as Soeren was replying.

[Jak24]

HI

....sorry i mixed up the current sensing pin with the enable pin .....
PS: one current sense pin is for one motor the other one is for the other motor:D
sorry again ...

Regards

Jak24