Hi Prithul271176
I got your last post you posted by Email.
If you have been unable to load the Forum pages you may not have seen the reply I posted to Dan so I will copy the text in this post to you and it might arrive in Email.
Copy:
Hi Dan and All.
Not really a trick and is easily explainable. When you use one of the electronic “H” bridge type controllers you cannot “creep” a motor from standstill. The reason is to do with the flywheel diode(s). If you care to analyse the circuit you will see (for most of them anyway) that there is never a diode DIRECTLY across the motor. One always has to connect via the motor supply.
If you connect an oscilloscope directly across the motor you will see the positive PWM pulsed but also a negative pulse which at low speeds cancels out the wanted PWM with a net result of zero volts at the motor. This situation remains with the negative pulse matching the PWM until a point is reached where the PWM is slightly wider. This is when the motor starts to move and once started the negative pulse reduces in width rapidly and all of a sudden the motor is spinning at about 25 or 30% of full speed. Once moving the PWM can be reduced to slow the motor to a very slow speed but due to all of this the motor cannot be started very slowly.
I did post this a few years ago and offered to follow up in detail with oscilloscope pics but the post did not generate any interest so I just assumed that everyone knew all about this problem and so I did not bother further.
Some application like a motorised focus control or remote control golf buggy need to creep a motor slowly from standstill so the reversing is done with a relay where a flywheel diode can be directly connected.
Cheers Bob
End copy.
Cheers Bob
