Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

PIC microcontroller stops working why?

Status
Not open for further replies.
A

anan1975

Member level 3
Joined
Aug 10, 2009
Messages
57
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Location
Noida india
Activity points
1,662
Dear all,
In my Pic 16F675 Project some time mcro stops working during electrial spikes,
I used WDT to reset but sometime its WDT also not workes and circuit Needs to be restart,
My project is Based on Live Pover supply made by 220 V AC to 12 volt dc by reducing down it by series capacitor shunted by a 12V/1W zener and then regulated by 78L05 decopled by PF and elctrolytic capacitors.
Please suggest to overcome from the prblem of hanging of microcontroller.
Regards
Anand
 

the series cap will faithfully pass the spike to circuit.
this type of config is not recommended for digital circuits especially microcontrollers.

whatever circuit you add , you will encounter random problems in use. it will be a
headache in operation.

change the supply to a 7805 or any other trfr based one.

srizbf
26thjune2010
 

Dear sir,
But I have used one 78L05 after making 12V from the mains 220V supply decopeled well.

AC i/p-->>series capacitor-->rectifier-->resister-->>zener+filtercapacitor-->>78L05-->decopling capacitor--->inductor-->>ceramic decoupling capacitor-->> microcontroller.


Regards
Anand
 

better is to use a transformer based supply.

since you have the said configuration already try the following modifications:

in the 78l05 connect ceramic caps of 0.33uf in both 'in ' and 'out ' pins to ground.
what value is the inductor?

srizbf
26thjune2010
 

Dear sir,
used capacitors are 0.1 mfd myler at in and out .And 100mfd at o/p of 78L05 and a 470 MFD at i/p of 78L05.
regards
Anand
 

have 0.1/0.22/0.33uf in the Vdd and Vss pins of pic.
solder it close to the pins.

srizbf
26thjune2010
 

Dear sir,
exactly soldered 0.1MFD myler on PIN no 1&8 from the back side of PCB.
And also used a good quality Glass epoxy PCB.
Regrds
Anand
 

only option leftout is change 'inductor'

what value is current one ?

increase whatever it is .

srizbf
26thjune2010
 

Dear sir,
The value of inductor is 10 micro Henery.

but no problem if it hangs out but it should be reset by WDT .

Many Times it Never reset by WDT of micro is it possible that internal WDT rc oscillator also stops working.


Regards
Anand
 

all supply disturbance affect WDT also.
its value becomes indeterminate. other mode bits also get astry.

a good supply will overcome such problems.

srizbf
26thjune2010
 

Dear sir,
is it not possibal that when mirocontroller stop working WDT should reset it.
And when WDT stop working microcontroller should reset it.
Regards
anand
 

if both WDT and controller are monitoring other ones functions ,
they can do it only when they have proper feed(pwr).

if both of them get pwr from same line (assuming pwr disturbance as the cause)
then restting cannot be expected.

srizbf
26thjune2010
 

dear sir,
Is it better to use PIC12F510 in spite of pic 16f675 because in its datasheet it is mention many time that it is used for fully static operation.
regards
Anand
 

a static operation refers for clock freq.
generaly a static specified controller will preserve state when you remove clock from mcu to conserve power.

dont know (possibly it cannot be) whether clock can be made static for WDT.

the datasheet may throw the light on which sections are affected.

srizbf
26thjune2010
 

are you sure about your XTAL caps?they must be between 22 and 33 pf depanded on your frequency
 

Dear sir,
I M not using external oscillator. only using internal oscillator of pic 16f675.
regards
Anand.
 

anan1975 said:
Dear all,
In my Pic 16F675 Project some time mcro stops working during electrial spikes,
I used WDT to reset but sometime its WDT also not workes and circuit Needs to be restart,
My project is Based on Live Pover supply made by 220 V AC to 12 volt dc by reducing down it by series capacitor shunted by a 12V/1W zener and then regulated by 78L05 decopled by PF and elctrolytic capacitors.
Please suggest to overcome from the prblem of hanging of microcontroller.
Regards
Anand
Click to expand...

What type of electrical spikes?

Post your full circuit, this will help to locate the problem exactly

Nandhu
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top