Power supply spikes!!!!

[krunal_299]

Hi to alll!
Recently i have one project of stepper motor control designed by someone else.
The problem is : the programming of microcontroller gets blown very offten upon switching the mains power switch.
Here is circuit detail:
PIC microcontroller
Stepper Driver :l298
Power supply: unregulated +24v for motor H-bridge.
Regulated +5v for logic supply. Both supply share same ground.
4700 micrfarade capacitor is connected at +24 v terminal without discharging resistor.


So can anyone make suggestion on it?

And also let me have some techniqe to discharge 24volt rapidly other than simple bleeder resistor.

 

[ericgibbs]

Hi to alll!
Recently i have one project of stepper motor control designed by someone else.
The problem is : the programming of microcontroller gets blown very offten upon switching the mains power switch.
Here is circuit detail:
PIC microcontroller
Stepper Driver :l298
Power supply: unregulated +24v for motor H-bridge.
Regulated +5v for logic supply. Both supply share same ground.
4700 micrfarade capacitor is connected at +24 v terminal without discharging resistor.


So can anyone make suggestion on it?

And also let me have some techniqe to discharge 24volt rapidly other than simple bleeder resistor.

hi,
Is there any capacitive decoupling on the +5V supply? if so, what?

When you say the PIC gets 'blown' do you mean the program is corrupted?

Are all the PIC ISP pins correctly programmed and terminated? , thats is, not 'floating'?

Do you have a drawing to post

 

[krunal_299]

Yes, there is +5v capacitive decoupling at IC pin.
yup, the program gets corrupted.
motor does not run but after reprogramming the chip it does !
For schematic I will have to draw to be posted here.
i will but it will take some time for me . . . ok!
One more thing i wish to clearify that is : If filtering capacitor remains charged after the mains switch OFF (as there is no discharging path for that capacitor at all), what would be the effecton circuit, upon switching ON the mains in just 1 second after it was being switched OFF?

 

[ericgibbs]

One more thing i wish to clearify that is : If filtering capacitor remains charged after the mains switch OFF (as there is no discharging path for that capacitor at all), what would be the effecton circuit, upon switching ON the mains in just 1 second after it was being switched OFF?

What can happen with a large cap and very light load is that PIC reset line dosn't go low enough by the time you reswitch ON.. so no hardware reset!
Its possible to add a simple push switch on the PIC's reset pin, in order to check/test during debugging.

As you hav'nt said what type of PIC it is and not posted the program its difficult to say what the problem really is.

 

[krunal_299]

Oh so sorry! my mistake is there!
The microcontroller used is of phillips 89v51rd2.
At about the program, that is not handy to me yet.
As soon as i get it will be posted immediately.
Hhh.... and one more thing : In circuit design there is no reset switch provided by the designer.