Hello,
I am trying to make a small RC car with legos arduino and some nrf modules with some joysticks.
I have a 12v DC brushed motor (370) powered by 10*1.2 (AAA) 2600mAh batteries, and drived by L293D.
The motor is not really powerull, but enough to drive the car slowly on plane surface.
When I first push my forward joystick the motor works fine, but if I stop the motor (LOW,LOW on both L293D control pins) then it won't start back.
But if I push the car by hand (to rotate a bit the motor) then the motor starts to work again. the motor has 0.1uF capacitor between + and - on cylinder.

Any idea what could cause that ?

 

Is the motor ok straight on the battery?
First test it without the controller. It sounds like you have some problems. The car should move quite fast. If it is struggling to move, fix that first.

 

Hello,
I am trying to make a small RC car with legos arduino and some nrf modules with some joysticks.
I have a 12v DC brushed motor (370) powered by 10*1.2 (AAA) 2600mAh batteries, and drived by L293D.
The motor is not really powerull, but enough to drive the car slowly on plane surface.
When I first push my forward joystick the motor works fine, but if I stop the motor (LOW,LOW on both L293D control pins) then it won't start back.
But if I push the car by hand (to rotate a bit the motor) then the motor starts to work again. the motor has 0.1uF capacitor between + and - on cylinder.

Any idea what could cause that ?

The motor is too weak to overcome "stiction" of the various mechanical components including wheels to surface, axles to wheels and so-on. You either need to add gearing to increase torque to the wheels, use smaller diameter wheels (a type of gearing or altering torque), or, lubricating axles with very light silicone oil.

 

@dendad without controller wired straight to battery the motor is slighty faster. But I guess its due to the drop of the L293D (that its a bit slower than with it)
@GopherT I have reduction gears, the torque is already high.

The main problem is not that is drives slow, is that it starts well, but when I stop the car it won't start again until I just move a bit the axle of the motor, I am not pushing while I send power to motor, the car is stopped when I push it, really just to turn a bit axle of the DC motor.

Like, I push joystick, car drives, I put joystick to stop mode (iddle positon) car stops, I push joystick no reaction, I push little bit the car while stopped, then push joystick and it drives again, its really weird like there is a dead axle angle (or what ever it;s called ) at some point. that prevent power to go through motor?

 

@dendad without controller wired straight to battery the motor is slighty faster. But I guess its due to the drop of the L293D (that its a bit slower than with it)
@GopherT I have reduction gears, the torque is already high.

The main problem is not that is drives slow, is that it starts well, but when I stop the car it won't start again until I just move a bit the axle of the motor, I am not pushing while I send power to motor, the car is stopped when I push it, really just to turn a bit axle of the DC motor.

Like, I push joystick, car drives, I put joystick to stop mode (iddle positon) car stops, I push joystick no reaction, I push little bit the car while stopped, then push joystick and it drives again, its really weird like there is a dead axle angle (or what ever it;s called ) at some point. that prevent power to go through motor?

Then it is a "cogging" issue. This happens with motors with a low number of poles (3?). If the motor stops where a permanent magnet is aligned with a winding (and a motor preferentially stops that way), then it has the least possible torque for the next start. You can try reversing the motor for a split second (gear lash will let it move) then slamming it forward.

 

Sounds to me like a dirty commutator or brushes on the motor. Sometimes it goes, sometimes it stops on that dead spot. And the dead spot is probably there because, as GopherT said, they tend to like to stop in certain orientations, meaning if the motor stops in the same place all the time and can't go again unless you push it a little, yeah, I could see a problem developing at that location on the motor commutator. You have nothing to lose by spraying the motor commutator with some contact cleaner. If it cures the problem - great. If not - oh well. At least you didn't spend thousands of dollars.

 

Thank you for you replies, I will try that, I have few motors like that I will also try with the others