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I have a microcontroller that is supposed to drive three motors (only one needs to be driven at the time). I tried doing this with two L293D's but there's a problem with braking.

The problem is that they don't brake fast enough (the motor just continues going for a while). These motors are NXT Interactive Servo Motors and normally they are driven by a NXT Intelligent Brick but I want to do this with a microcontroller. These motors have two pins to go forward or backwards, ground, 5v for the optical sensor and 2 outputs returning from those sensors to give feedback on how far the motor has gone.

Normally if you put the same voltage on both the driving pins of the motors, they should break but they don't... I found some information on why this is happening on another site and I think I'll have to get another IC to do the job.

I was thinking of using the same IC as the Intelligent brick uses but I want to be sure that these actually brake like I want.

So this is the question: Does the LB1836M make the motor immediately stop if you send 0V to both input pins?

Any suggestions of other ic's or perhaps a solution to make the motors break while using the l293D's are always welcome.

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There is already a lot of good information given at the forum link that you posted. I think it is possible to conclude that the L293D is not a great driver for performing the motor braking operation. The output diodes and Darlington output stages leave the motor coasting when the voltage gets low enough that it cannot bias the output stages. You really need a MOSFET type driver that is specifically designed for motor breaking that can hold the necessary low impedance connections to GND on both sides of the motor all the way down to near zero volts.

Your question "Does the LB1836M make the motor immediately stop if you send 0V to both input pins?" cannot be answered in the affirmative. Simple inertia with practical physical laws says that there will be no immediate possible.

The LB1836M driver chip will be better than the L293D when it comes to trying to do a braking. This device is still made with bipolar transistor circuitry so will still not be as effective as a driver setup with MOSFET output transistors.

Note that there are driver chips from companies such as Allergo and others that have all the bridge control logic that you then connect to your own output MOSFETs to form the necessary H-bridges. I've used a some of those in designs and liked the results.

Since you are anticipating the use of a microcontroller to drive your device you may want to consider the idea of braking through the use of reversing the drive to the motor through a PWM technique. This was discussed in the thread that you linked and can be a suitable way to quickly slow your motor using even the bridge driver chip that you have now. You would just have to make sure that your microcontroller has the necessary timer logic to generate the PWMs and that you can prepare the necessary software to profile the PWMs being generated into the necessary deceleration profile for your motors.

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