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Topic: Connect LM298 with two power supplies  (Read 700 times) previous topic - next topic

mhubris

Hello every one im new at arduino, so forgive me if im doing something thats wrong. Im working with motor drivers(LM298) trying to  make one car controlled by arduino supplied with two different batteries. So i build one schematic like the one that i send in attachments. The problem is that i only have 2.5V in the outputs, and sometimes less than this in the left motors. I need more power, like the 6v of my battery. What im doing wrong?
Best Regards

vinceherman

My understanding is that motor drivers based on the 298 series are old technology with a large voltage drop.
Kind of exactly what you see.

More modern drivers are available
https://www.pololu.com/product/2130

slipstick

If you want 6V out of that sort of driver you'll need about 9V in. And I don't mean a little rectangular 9V battery. Something like 6 x AA cells would do the job.

Steve

mhubris

If you want 6V out of that sort of driver you'll need about 9V in. And I don't mean a little rectangular 9V battery. Something like 6 x AA cells would do the job.

Steve
But its normal this drop?

slipstick

It is with LM298, particularly if you're trying to draw high currents (like with motors). Modern motor drivers are a lot better as vinceherman said.

You didn't say what type of batteries you are using. Some batteries will themselves lose a lot of voltage if you try to take too much current out of them, so that could also be part of the problem. Have you tried measuring the battery voltage while the motors are running? Is it still 6V?

Steve

mhubris

It is with LM298, particularly if you're trying to draw high currents (like with motors). Modern motor drivers are a lot better as vinceherman said.

You didn't say what type of batteries you are using. Some batteries will themselves lose a lot of voltage if you try to take too much current out of them, so that could also be part of the problem. Have you tried measuring the battery voltage while the motors are running? Is it still 6V?

Steve
Im using 4 AA alkaline cells. And when the motors are turned on the voltage drops to 4.8V in the batterys. Which kind of 12V batterie do you recomend me? LIPo? Its not a problem becouse of voltage drops?

slipstick

Why have you suddenly decided you need 12V? I would have tried first with 6 AA NiMH rechargable cells. They can usually deliver more current than alkalines and that should give you about 6V to the motors.

But if you do want a higher voltage then a 3S 11.1V lipo would be good. But make sure you get one with a C-rating of at least 20C e.g. https://hobbyking.com/en_us/turnigy-2200mah-3s-25c-lipo-pack.html

Most of those from the RC hobby suppliers are fine but some suppliers like Adafruit sell Lipos with very low C and they suffer from voltage drops like alkaline batteries do.

Steve

TomGeorge

Hi.
OPs diagram;


Can you post a link to specs/data of your motors, please?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

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