Controlling startup speed for dc motors

[mahaju]

Hi
Could you please tell me how to start dc motor so that it starts slow, that is, I need to avoid the initial jerks when my manually controlled robot starts. Could you please tell me the methods of doing it?

Thanks for your help in advance.

 

[banjo]

The usual method to do this is to use pulse-width modulation. The idea is that you subject the DC motor to the full operating voltage, but limit the duty cycle. The larger the duty cycle, the faster the motor turns.

If you control a DC motor using a linear regulator, then the motor has problems starting at slow speeds under load. This is because the reduced voltage is limiting the motor's torque. Since more torque is needed to overcome the initial friction, you get motors that either stall or start with a jerky nature.

The pulse-width modulation is best done with a microcontroller. That way you can tailor the parameters to the motors you are using. For example, you may need a very high duty cycle for a couple of milli-seconds to get the motor going before ramping back to the required duty cycle.

 

[nikhil_damle]

insitially identify the uc so that it can be used to genertate a pwm use the longset dealy in the pwm cycle the motor will start slow thne alter the delay to gain sped

 

[vsmGuy]

This technique is called softstart.

Now use google.

 

[~E3016~]

The main idea of this starting problem is using the series resistance in the rotor, so the current in the rotor is low. when the motor is stable enough, you can lower this series resistance value...

 

[vsmGuy]

Using a series resistance is a very bad idea for automated systems...

In mechanical systems, it's possible to disconnect/decrease the series resistance after start, but in automated systems choppers or PWM softstart is definitely a better choice!

 

[maggots]

if U want to control speed of motor DC U must control voltage input to the motor.... So U will control it microcontroller with PWM (Pulse Width Modulation)... so all U have to do search microcontroller who have feature like PWM!!like atmega

and U make pwm by set timer !!or in atmega U use OCX(x for 0 to 2) and connected to h bridge ..oh ya make sure that U set that the microcontroller is connected....to controlled u set OCR !!

if still confuse U can contact by PM..!!