l298 dual motor drive

EDAboard.com Forum Index -> Robotics and Automatics Forum -> l298 dual motor drive

Author

Message

adick

Joined: 01 Dec 2004
Posts: 19

19 Jan 2005 12:54 l298 application

hi all,
i'e build a wheeled robot, and i'm going to use l298 to drive the motors of its two wheels. i got the circuit from the internet.
The problem is i have try that circuit three times but the chip always burnt out.
So, help me please...?

Sorry, but you need login in to view this attachment

nicleo

Joined: 06 Sep 2004
Posts: 717
Helped: 60

19 Jan 2005 13:04 l298 diodes

Would you pls advise the rating of your motor?

VVV

Joined: 26 Nov 2004
Posts: 1584
Helped: 290

19 Jan 2005 19:09 l298 motor driver

The schematic looks OK, other than the fact that you do not have any means of sensing the motor current. That may or may not be a problem. What is the motor current?

At this point I would suspect a wiring problem. Please check carefully the pin numbers for the package you have, as well as the polarity of the diodes. Are the diodes OK?

tocal09

Joined: 12 Jan 2005
Posts: 62

21 Jan 2005 2:28 l298 diode

If I use 1A diode (pr1003). The L298 --->die ???

VVV

Joined: 26 Nov 2004
Posts: 1584
Helped: 290

21 Jan 2005 18:36 l298 dc motor circuit

The L298 datasheet recommends Schottky diodes. In the application diagram they specify some 200ns diodes. Your PR1003 has 150ns of recovery time, so they should work. I am a little confused... Do you have any Schottky diodes to try?

Did those three chips fail instantly, or did they work for a while? And what is the voltage/ current rating of the motor? What kind of battery are you using? You may need to implement current limiting if the motor rating is close to the rating of the L298 (3A). And I hope you are not exceeding the maximum voltage of the L298.
Please post a few more details.

adick

Joined: 01 Dec 2004
Posts: 19

23 Jan 2005 11:44 l298 parallel diode with motor

the first one burnt instsntly, but the other two works for a while then it burnt.
the rating of my motor is 24V/3A
i used MR 820 fasat recovery diodes.

VVV

Joined: 26 Nov 2004
Posts: 1584
Helped: 290

23 Jan 2005 20:23 circuit drive dual motor l298

Since the current rating of the motor is exactly equal to the maximum rating of the L298, you must include current limiting, to make sure the current never gets above that. It could happen because of a variation in the 24V power and mostly at motor startup.

To implement current limiting, insert a low resistor in series with pin 15 and compare the voltage across it with a reference voltage. The output of the comparator should be used to drive the Enable pin (11). So the motor current will be limited to 3A. For example, using a 0.1Ω resistor you would only lose 0.3V across it at 3A and your reference should be, of course, 0.3V.
Take a look at the circuit. It will chop the motor voltage, causing the maximum average motor current to stay at about 3A. The switching frequency can be adjusted by changing C2. The rest of the circuit stays as you have it, with diodes and everything.

I think the diodes you used are OK.

Sorry, but you need login in to view this attachment

adick

Joined: 01 Dec 2004
Posts: 19

24 Jan 2005 11:27 l 298

Thanx for your explanations.
One more question:
into which pin should i apply pwm signal, incase i need to do it? pin 11, 10 or 12?

VVV

Joined: 26 Nov 2004
Posts: 1584
Helped: 290

24 Jan 2005 18:26 l298 circuit -l297

Pin 11 is the best, since you only need one signal to turn off all transistors in the bridge, so you only need one gate.

One more thing: to test the circuit, you can start with a resistor much larger than 0.1Ω. That will limit the current to much less than 3A. It's easier to see if the circuit is working, since the torque will be limited, so you will see the speed decrease as soon as there is any load on the motor.
I would also try first with less thatn 24V, say 12V, again to limit the possiblity of damaging the IC in case something goes wrong. Once you are confident the circuit works, you can bring the voltage up to 24V and then bring the current up to 3A.

Google
AdSense
Google Adsense

24 Jan 2005 18:26 Ads

adick

Joined: 01 Dec 2004
Posts: 19

27 Jan 2005 20:12 l298 motor driver datasheet

Thanx for your advice.
Just one more thing, my friend advising me to join the inputs (A&B) and outputs together so that the chip can stand current greater than 3 A. I think that could work, but then i have to use one chip to control only 1 motor.
Any comments?

VVV

Joined: 26 Nov 2004
Posts: 1584
Helped: 290

29 Jan 2005 22:14 dual l298 motor driver

Yes, the datasheet states that you can parallel the corresponding outputs of the two channels to double the available current. Of course, if you do that, you will need one chip for each motor.
The circuit I suggested should work. You should test it, maybe with a smaller motor, until you are sure it works. Then you can limit the current to a safe value and never worry about it, even if the motor stalls.
The other half of the LM393 can be used for the other channel.

seinfield

Joined: 12 Dec 2001
Posts: 41
Location: Mexico

30 Jan 2005 1:47 l298 current limit

i had the sam eproblem with the l293D, the ic just burn out when i used more than 5v to drive the motor. The chip has a F in the Label, i think that it was form fairchild, but then i received my samples from TI and they worked ok. i applied more thn 24 volts and they were working very good.
Try to change the ic maufacturer.

5ive5

Joined: 14 May 2009
Posts: 1

14 May 2009 20:32 l298 current limiting

hi, need help regarding to L298 motor driver.

i use this chip to run a dc motor running at 4v which can consume up to 2.5 amperes. However, it didn't give me the maximum torque i was expecting while running via the chip.

I changed the Rsense resistor of 10ohm to 1ohm, and it works better as I can feel the higher torque although i'm not sure if i have chosen the right resistor. I measured using a multimeter directly onto this 1ohm and suprisingly after a while, the resistor burnt.

My questions are:
1. How the Rsense works actually? Initially, I thought i could just put some low value resistor for the Rsense. And, what value would you recommend?
2. Should I get a Power Resistor for the Rsense. i.e., 3W 0.5ohm ?

Thanks!

best regards

Very Happy

miltinhu

Joined: 22 Jul 2009
Posts: 1
Location: belém

22 Jul 2009 22:47 dc motor circuit, l298

qnt ao diodo usei um retificador e funfo...ta perfeito...

utilizei o circuito do datasheet sem problema nenhum...so tens q ver a corrente do motor....

pq se naum me engano a corrente max do l298 é 2A

Sorry, but you need login in to view this attachment