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I have a L298N and I want to use it to drive two DC motors. The problem I face is that one motor is working at ~7.2V and the other one at 3.3V (it's a car, the 3.3v motor is used for steering). I will drive it with an Arduino, depedending from the data received from other sensors.

Now, I'm asking you if you can help me with some ideas to design something in order to be able to use both of them with the same L298N.

Thanks !

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  • \$\begingroup\$ With careful design to limit PWM duty cycle you can probably use the same voltage for both, but replace the horribly antiquated and lossy L298 with a modern FET bridge. Its also probably easy to source a higher voltage wound version of the small motor or at least one with compatible housing and shaft size. \$\endgroup\$ – Chris Stratton Oct 31 '16 at 18:41
  • \$\begingroup\$ @ChrisStratton any recommendations ? Thanks ! \$\endgroup\$ – Philip Coandă Oct 31 '16 at 18:43
  • \$\begingroup\$ If within your curent needs the TB6512FNG already mentioned may work. But beyond a smaller toy you may want discrete FETs for the drive motor. Cheap RC ESCs may be able to be reworked. Also consider a cheap servo for steering. \$\endgroup\$ – Chris Stratton Oct 31 '16 at 18:45
  • \$\begingroup\$ @ChrisStratton thanks ! The 7.2V motor draws ~1.7A at the begining, then is stabilized ~600mA. I think that the servo option is, somehow, the best in this case, but I tried to keep the car as simple as possible. \$\endgroup\$ – Philip Coandă Oct 31 '16 at 19:03
  • \$\begingroup\$ Your drive motor's current draw will go back up when it stalls, so you either need to be okay with whatever your chosen driver does when the rated current is exceeded, or else design in a limit mechanism. As mentioned before, drive motors usually use discrete FETs - higher current bridges are available but not cheap. \$\endgroup\$ – Chris Stratton Oct 31 '16 at 19:15
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You cannot use L298 at all unless you account for high dropout voltage.

These have totem pole bipolar drivers and you must use a MOSFET bridge or motor driver with deadtime control for low 3.3~5V motors. Otherwise your torque will be very inconsistent with temp and load and your 7.6V motor will never get full voltage or speed.

see datasheet for total drop voltage below;

enter image description here

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The simplest answer here is to simply use two L298N parts. Once for each motor. Even though the L298N supports two bridge drivers they both must be used at the same voltage.

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  • \$\begingroup\$ Well, yes, but I want to minimize the power loss, it's supposed to last as long as possible. I was thinking to use transistors as switches to redirect the signals from the driver and a voltage divider for the 3.3V motor. \$\endgroup\$ – Philip Coandă Oct 31 '16 at 18:19
  • \$\begingroup\$ Actually one shouldn't use an L298 in battery powered devices at all. It's horrible and long outdated. \$\endgroup\$ – Chris Stratton Oct 31 '16 at 18:39
  • \$\begingroup\$ @PhilipCoandă no please do not use a voltage divider to power a motor \$\endgroup\$ – KyranF Oct 31 '16 at 18:39
  • \$\begingroup\$ @ChrisStratton I agree. it's a shitty old darlington driver, that 3.3V probaly only gets to 2V output due to the drop in the L298. It's the worst possible motor driver i've ever seen and I hate it how people keep using it even today. The Toshiba TB6612FNG on the carrier board from Pololu is a great option though. \$\endgroup\$ – KyranF Oct 31 '16 at 18:40

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