DC motor spikes cause error

[codeeater]

Hi,

I am trying to drive this DC motor with an LMD18200 motor controller controlled by an Atmega644p, however I am having big issues.

My projects runs on a 12v 5A supply. 5v is produced by a Voltage Regulator which is used to power the uC. There are 10uF capacitors from 12v>GND and from 5v>GND. The motor controller is connected to the 12v (but controlled by 5v logic) which is used to drive the motor. There is a 2200uF cap from 12v>GND right beside the motor controller.

However, when I try to run the motor, the uC just stops working correctly and the motor makes a click but doesn't move. Using another motor works fine, and if I use separate power supplies for the motor and the uC there is no issue, the motor runs just fine.

This indicates to me that there is an issue with voltage spikes from the DC motor. However, with all of this in place, I can't think of much else I can do to reduce these spikes.
Can someone please help!

Thanks

 

[Usama Siddiqui]

bro the problem is that the motor has coils that provides the reverse current,when u mix the ground of power supply together with that of microcontroller then mictrocontroller will not be constant in its current and it would work abnormally,what we do is that simply use an optocoupler between the uC and the motors(motors is provided with its power supply), what it does is that it isolates the uC with the motors and therfore the reverse current is drained within the hbridge circuitry.
pc817 is the most common optocoupler found.

 

[codeeater]

Thanks for the response
The problem with using optocouplers is that they cannot supply enough current for the motor to run. I need around 3A.

There must be a way to remove spikes while still using an H bridge.

 

[Usama Siddiqui]

dude the optocoupler is driven by the uC only,it has 2 parts,the second part of optocoupler is conncted to the hbridge,rather then providing the signal to the motor directly u just use an optocoupler in between,now u can use anyyyyy power depending upon your hbridge for motor driving. thats not an issue.
basically what the prime target of optocoupler is that it separates the ground,the end connected to uC is provided ground of uC,and the other end i.e connected to hbridge is grounded with the ground of the power source with which the motors+hridge is being run.

 

[codeeater]

Oh I see! That is one possibility! But I do not need to separate GND because it works if I simply have a power supply for the uC and a power supply for the motor with a shared ground. I want to be able to share the power supply.

 

[Usama Siddiqui]

yes u can share the ground aswell,the reverse current would get sinked into the ground without disturbing the uC .