L298n voltage loss

[Jak24]

Hi!

I just recently realized that the reason that my robot is slower than calculated, could be the voltage loss in the l298n.
I am using a 12v battery to power a (3)12v motors, and turns out the l298n gives the motor only 10.8 , so the loss is 1.2 v.
When my battery is fully charged (13,8 v) then it gives 12.6,
my question is:
Is there any way to get rid of the voltage loss, is there a better h-bridge chip, or are they all pretty much the same?

Thanks

Regards
Jak24

[DUKELancelot]

The LMD18200 H-bridge is what you are looking for. It uses MOSFETs so it doesn't get really hot like the L298 (which uses bi-polar transistors and provides a significant voltage drop to the motor).  It also has built in flyback diodes, so you don't need external diodes like with the L298.  The disadvantage is that there is only 1 H-bridge per package, whereas the L298 has 2 (a dual H-bridge).  This makes the L298 cheaper to use.

Also 1V do you actually thank that will make a difference. Did your calculations take into account weight, fraction and that the rated RPM of your motors is for no load , so under load they will drop a considerably amount like 20-30%.
 

[Soeren]

Hi,

I just recently realized that the reason that my robot is slower than calculated, could be the voltage loss in the l298n.

Easy to test - wire one of the motors around the L298 (i.e. let it get full speed) and compare.
However... Calculating the exact top speed of a vehicle is next to impossible unless ALL factors are known.

Is there any way to get rid of the voltage loss, is there a better h-bridge chip, or are they all pretty much the same?

There are lots of better bridges, but did you consider a relay and a single power MOSFET per motor?

[Jak24]

Hi!

The LMD18200 H-bridge is what you are looking for. It uses MOSFETs so it doesn't get really hot like the L298 (which uses bi-polar transistors and provides a significant voltage drop to the motor).  It also has built in flyback diodes, so you don't need external diodes like with the L298.  The disadvantage is that there is only 1 H-bridge per package, whereas the L298 has 2 (a dual H-bridge).  This makes the L298 cheaper to use.

Also 1V do you actually thank that will make a difference. Did your calculations take into account weight, fraction and that the rated RPM of your motors is for no load , so under load they will drop a considerably amount like 20-30%.
 

Yeah that h-bridge might be a better consideration.

Hi,

I just recently realized that the reason that my robot is slower than calculated, could be the voltage loss in the l298n.

Easy to test - wire one of the motors around the L298 (i.e. let it get full speed) and compare.

I tested it like that, i got about 15% more speed

However... Calculating the exact top speed of a vehicle is next to impossible unless ALL factors are known.

Yeah, when i did my calculations I only considered the main factors, and i didn't consider things like:
loss in friction, losses in motor (as it doesn't always preform the nominal speed/torque) etc...

Is there any way to get rid of the voltage loss, is there a better h-bridge chip, or are they all pretty much the same?

There are lots of better bridges, but did you consider a relay and a single power MOSFET per motor?

wouldn't that only allow the motor to turn in one direction?

Thanks

Regards
Jak24

[Soeren]

Hi,

I tested it like that, i got about 15% more speed

Oh, then it's surely worth going for a better solution.

There are lots of better bridges, but did you consider a relay and a single power MOSFET per motor?

wouldn't that only allow the motor to turn in one direction?

No, the relay controls the direction and the MOSFET controls the speed.
Here is a circuit I've posted before.