Let's Make Robots!

L298N Motor Driver Circuit Problem

Dear LMR,

For some reason I am really struggling with implementing a simple L298N motor driver. I have a simple breadboard robot and I am trying to run a Timya dual gearbox off the driver. I made a recommended circuit from the data-sheet but for some reason when I pull one of the inputs high (by connecting it to 5V power rail) the motor driver does not activate the motor outputs. I used an oscilloscope to measure all the voltages and everything is as it should be but for some reason the outputs always remain grounded. I could appreciate some help as I do not know what I am doing wrong. I have read forums related to this on LMR and have not found a solution. Bellow are pictures of the connections and the circuit. I have also attached the data sheet.

Thanks,
Gonzik

PS I have tried changing the L298N driver and I get the same result so it is not a case of the driver being fried.


Robot


Circuit

Recommended Circuit

 



My Connections

SOLUTION (synopsis):

My setup worked when I used this schematic: http://www.solarbotics.com/assets/schematics/solarbotics-l298_schematic_complete.jpg

The original setup was wrong because Vss of 5v is needed for logic and Vs for motor power must be at least Vss + 2.5V. I was trying to use 5V for both. From my understanding this difference is necessary to bias the internal transistors of the driver.

Thanks to everyone who helped!


AttachmentSize
L298N-Motor_Driver.pdf190.37 KB

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

just give a try,.,.without diodes.,,., it will smoothly run.,.,

 

dude, did you get this working?

Hey thanks for actually caring if I got this working :) Sorry it took me so long to get back to you guys, I just moved to a new city and it took me a while to set up shop again ;)

Solarbotics has a L298n breakoutish board http://www.solarbotics.com/products/k_cmd/

More interesting is the schematic: http://www.solarbotics.com/assets/schematics/solarbotics-l298_schematic_complete.jpg

Gonzik, do you using this schematic?

Hey Markus thanks for that schematic. I was able to get it working =) I am not sure what was wrong with the one provided in the data sheet. I have one thing I don't understand though. What is the purpose of the two 47K resistors? Is it to make sure that the enable input is not left floating at any point?

You say you are pulling one of the inputs high, are you pulling the other one low at the same time?  I dont think your motor will turn if one of the inputs is left floating. 

Thanks I got it working. The solarbotics schematic is able to handle one input left floating though.

You can cross reference the schematic of my Bluetooth RC tank if you like.  Make sure you use two different supplies; Vss of 5v for logic and Vs for motor power that is at least Vss + 2.5V

Hi Gonzik,

Check the polarity of the diodes. I had the case that the marking on several diodes were wrong.