i need a help about PIC with a DC motor

[DTMF]

hi i have a probleme in this circuit & i need a help to solve it

when i press stop button i send a 00 to the portb

wich mean T1 T2 T3 T4 are stopped

but the DC motor does not stop immediatly

it continue to spin despite D1 D2 D3 D4

what should i do ?

 

[DTMF]

sorry instead of T1 T2 T3 T4 i mean Q1 Q2 Q3 Q4

 

[Nigel Goodwin]

hi i have a probleme in this circuit & i need a help to solve it

when i press stop button i send a 00 to the portb

wich mean T1 T2 T3 T4 are stopped

but the DC motor does not stop immediatly

it continue to spin despite D1 D2 D3 D4

what should i do ?

This is rather confusing?, because you ask about a DC motor, and your diagram says 'stepper motor'. But I'm presuming you mean DC motor, as a stepper can't possibly carry on rotating, as they don't really 'rotate'.

OK - I don't see why you mention the diodes?, they are there simply to prevent the back EMF from damaging the transistors, not to try and stop the motor. All your circuit is doing is removing the power to the motor, and it will simply freewheel to a halt - as any DC motor will!.

If you want it to stop more quickly you can 'short' it out, this provides substantial braking to the motor. In order to do this, you need to turn a pair of transistors ON - I would suggest the bottom two are best, make 100% sure the top two are OFF, or you will short the supply out. This should make it stop a lot faster!.

 

[DTMF]

1 st 10x

this is a DC motor & Q1 Q2 Q3 Q4 are just 4 rotating left & right

& about the diode i know that but didnt they must discharge th DC motor?

as a short circuit the DC motor on its pins

???????????????????

 

[Nigel Goodwin]

this is a DC motor & Q1 Q2 Q3 Q4 are just 4 rotating left & right

Turning the bottom two transistors ON (Q2 and Q4) shorts the motor out, this makes it stop a lot faster - it's a common and well known technique.

Some motor drive IC's even have an extra input pin which does just that, often labelled 'brake' or something similar.

If you want to stop the motor even more quickly, give it a short pulse in reverse - you need to time the pulse accurately in order to stop the motor as quickly as possible, without going backwards.

 

[Jay.slovak]

I kinda miss Base resistors for the transistors... you really should put them there...

 

[DTMF]

10x a lot Nigel Goodwin i really appreciate this

one more quetion

there is some ICs for stepper MOTOR control

do you know there names

& thank you again

 

[Nigel Goodwin]

one more quetion

there is some ICs for stepper MOTOR control

do you know there names

Depends what you mean?.

Do you mean to connect between a PIC and the stepper motor? (a simple driver), or one that does the complete stepping sequence for you?.

If you're using a PIC it's easy to generate the steps in software, and use simple driver transistors (or a ULN type driver chip) to feed the motor. It also give you far more control over the motor.

 

[DTMF]

ok 10x

but some times it easier

& better for saving memory

to use out drivers