Bidirectional 8V DC Motor Soft Start Circuit

[rhnrgn]

Hello,

I designed a circuit where i used DRV8837 as motor driver and PIC16f196 as MCU. I am driving 16DC motors at 8V at the same time independently. There is a DCtoDC Converter which convert 8V to 5V.

In some applications i faced voltage drop problems which causes MCU to Reset. Because if i start 16 motor at the same time they consume excessive power and causes reset at MCU.

That is why i am planing to add soft start circuit to every motor driver.

I did some research at internet and found some circuits but some of them for unidirection motor moves and some of them are really complex.

I need simple circuit.

Electrical specs are: 8V 40ma motor drive. 10ms voltage ramp is enough.

Here is my designed circuit:



Here is a softstart circuit that i found but i think this is for unidirectional motor drive:



Can you suggest me a simple softstart circuit like above but for bidirectional motor drive?

Thank You

 

[chuckey]

You have a MCU, use software to start the motors sequentially.
Frank

 

[rhnrgn]

Hello chuckey,

Thank you for your answer. Yes i can start them one by one but the problem is in some cases they need to be started at the same time. This is a part of very fast positioning system and miliseconds are important.

 

[chuckey]

Are you sure that there is enough decoupling on the motor supply lines? and the motor cases are earthed? Can you hold your MCU VCC (5V) up for 10mS - 10,000 MF?

Feed all the motors from a PSU, whose output is determined by your MCU (so you can software control the acceleration rate). There is a PSU IC LM 317, that will produce different voltage out via a control pin at a high current. So put one of these in series with your PSU and control the control pin from your MCU.
Frank

 

[rhnrgn]

Are you sure that there is enough decoupling on the motor supply lines? and the motor cases are earthed? Can you hold your MCU VCC (5V) up for 10mS - 10,000 MF?

Feed all the motors from a PSU, whose output is determined by your MCU (so you can software control the acceleration rate). There is a PSU IC LM 317, that will produce different voltage out via a control pin at a high current. So put one of these in series with your PSU and control the control pin from your MCU.
Frank

Thank you chuckey i will try it.