how to limit (current/voltage) of l298n outputs?

hello,
I have been working on a beginners project , "controlling RC car with (pic microcontroller / bluetooth module / l298n dual H-bridge)"
the car works well .. if i drive only 1 motor, but when i decide that i will go forward and left/right, well the driving motor speed almost died  even if there's no load on it , as well as the handelling motor , both motors r 6v , and i used 9v, 1A  then 12v , 1A , even the car was working so good with its old controlling board .
so i wanna know if it's a power consumption problem , or the H-bridge .
even i doubt it's a power problem cause it was working fine with x4 1.5V batteries with its old board.
thx.

sort by: active | newest | oldest
rickharris2 years ago

The L298 has a current limit at 2 to 3 amps. Your can motors may be causing it to limit. See the data sheet

http://www.st.com/web/en/resource/technical/docume...

omar emad (author)  rickharris2 years ago

2~3 A is way more than what my motors need , they r simple dc motors like which u find @ kids toys , in case they r in free running mode (low load)each will be drawing around 0.2~0.4 A , the only case in which i might cross 2A is when it's @ stall mode,

and when i tested it was @ free running mode and yet the speed dies.

solarbotics-regular-motor-2-B.jpg
omar emad (author)  omar emad2 years ago

my handelling system is so stupid that keeps the motor on a stall mode which will consume so much current something around 1.5A .. i guess that's the problem.

thx for mentioning the limit it was very helpful :D

iceng omar emad2 years ago

Good to hear.

Keep in mind the little 9 volt battery can only deliver 50ma for 18 minutes !

iceng2 years ago

Sorry, just disregard my previous comment. I read two motors and assumed two separate H-bridge ICs not a dual one.

Start over please,

The RC worked OK with the old controller what was it an L297 ?

I suspect your inputs as a probable cause of the problem.

The PIC may not be putting enough signal voltage to the L298. Have you measured the the inputs voltage ?

The Low input needs zero to 1.5vdc and a HIGH input needs 2.3vdc to 5vdc.

omar emad (author)  iceng2 years ago

inputs are fine low is 0 , high around 4.7v , and i connected enable pin to ccp (pwm) and it worked perfectly aswell, all r fine when its only 1 motor

iceng omar emad2 years ago

Need to understand you measured the inputs r also fine with both motors ?

Can you still use the old controller to compare readings ?

omar emad (author)  iceng2 years ago

all my reading r on 1 motor ,, pic input 4.7V high 0 volt low , l298n out around 7.8~8.2v when iam using 9v source.

when i use both motors ,, pic inputs r the same , l298n out drops to around 1.5~2v ,,

but i started to figure out the problem.

my handelling system is so stupid that keeps the motor on a stall mode which will consume so much current something around 1.5A .. i guess that's the problem

iceng2 years ago

Better decoupling the Electronic Controls from each other by a DIODE and a large electrolytic 220uF Capacitor with a o.47 film Capacitor for each.

omar emad (author)  iceng2 years ago

so it should be something like this i guess ?

if anything i need to add please notify me , and i will try it until i get ur answer.

L298N-module-schematic.jpg