Arduino H-Bridge problem

Alright so i got the code working. Pretty much turning a dc motor into a servo. Now im stuck. I am using a L298HN H-Bridge. When i hook up the h bridge and arduino circuit to this dc motor: BaneBots - PDX256 - 256:1 Gearmotor #PDX256 It works but the motor doesn't have enough power to move all the way its moves about 20 degrees then gets bogged down. I am using a 7.4v 2200mah lipo as the motor power source and that's what i get. I can attach that battery to the motor normally and it goes perfect. I have tried 12v batteries also and numerous power supplies all the way up to 15v with 3.5amps and still about 20 degrees of motion. I have tested the code with a smaller motor and it works fine, i also tried another h bridge L298HN and still the same thing.

That h-bridge can supply 2-3 Amps but even with no load the motor draws 1.5 Amps. If stalled it draws 148 AMPS!

If you turned it into a servo, then you have a problem on your shaft position control subsystem (sensor or software), on the code issuing the servo commands or on both.

johnwasser:
That h-bridge can supply 2-3 Amps but even with no load the motor draws 1.5 Amps. If stalled it draws 148 AMPS!

See but the weird thing is that when i hook up the lipo battery the motor is almost to powerful even with a load on it. Somewhere the h bridge is limiting the current or something.

Njay:
If you turned it into a servo, then you have a problem on your shaft position control subsystem (sensor or software), on the code issuing the servo commands or on both.

I have tested the code with a smaller motor and i don't actually have the sensor on the motor right now but am turning it by hand to test it. I set the speed to max and still nothing more than about 20 degrees.

Somewhere the h bridge is limiting the current or something.

That is right. It is limiting it to 2A because that is all it can handle before it shuts down. You need a smaller motor, or a bigger H bridge.

A motor requires more power to start than it does to continue running. For a 1.5A no-load motor, I wouldn't consider anything less than a 15A controller, maybe even more.

John_S:

Somewhere the h bridge is limiting the current or something.

That is right. It is limiting it to 2A because that is all it can handle before it shuts down. You need a smaller motor, or a bigger H bridge.

A motor requires more power to start than it does to continue running. For a 1.5A no-load motor, I wouldn't consider anything less than a 15A controller, maybe even more.

But again the weird thing is that i can power the motor with 2 amps fine and it works awesome but then when i go through the h bridge the motor just sucks. So i need an h bridge with something higher than 2 amp output? Im using this with arduino so any links to an arduino friendly shield or IC?

You haven't given details of the H-bridge circuit you are using. Are you certain that it implements current limiting? Most H-bridge boards I have seen using the L298n do not. OTOH the L298n does have over temperature protection, so if it is getting hot then lack of sufficient heatsinking may be part of the problem.

You can connect the two H-bridges in the L298 in parallel to increase the current rating from 2A to 3A.

The voltage drop of an L298n can be up to 4.9v @ 2A. So you will probably need to increase the voltage supply to the H-bridge.

Try measuring the voltage across the motor when it is turning and when it is stuck at 20 degrees. That should give you some ideas of what is going on.

I find the specifications of that motor hard to believe. A peak power of 0.55hp in such a small package seems unlikely - the motor would be dissipating around 400W while producing that output and would surely melt in no time. However, if the specifications are right, then you certainly need a bigger H-bridge, and I would also consider current limiting mandatory to limit the start current to a reasonable value.

dc42:
You haven't given details of the H-bridge circuit you are using. Are you certain that it implements current limiting? Most H-bridge boards I have seen using the L298n do not. OTOH the L298n does have over temperature protection, so if it is getting hot then lack of sufficient heatsinking may be part of the problem.

You can connect the two H-bridges in the L298 in parallel to increase the current rating from 2A to 3A.

The voltage drop of an L298n can be up to 4.9v @ 2A. So you will probably need to increase the voltage supply to the H-bridge.

Try measuring the voltage across the motor when it is turning and when it is stuck at 20 degrees. That should give you some ideas of what is going on.

I find the specifications of that motor hard to believe. A peak power of 0.55hp in such a small package seems unlikely - the motor would be dissipating around 400W while producing that output and would surely melt in no time. However, if the specifications are right, then you certainly need a bigger H-bridge, and I would also consider current limiting mandatory to limit the start current to a reasonable value.

This is how i have it hooked up: L298 DC Motor Control - Schematic | PyroElectro - News, Projects & Tutorials

i dont have a resistor on the current sensing pin though i found that the IC smoke so i got it working with just a wire. The lipo i have is 7.4v and 2200mah