Author Topic: 3 PIC16F877As blown by shorting Vdd and Vss (Read 4877 times)

BEAMer · « **on:** February 28, 2009, 12:04:17 PM »

hi,

I have been working with PIC micros for a long time, and there was no problem since i have been using it on a ZIF socket...

For another project, i was using the PIC on a bread board. and when i was using my multimeter to chk the voltage, i accidently shorted Vdd and Vss (i dont know why microchip designers have placed Vdd and Vss pins close together

). Thats it!! the PIC quietly went to REST IN PEACE.... i have already blown 3 PICs and my dad is like "No more PIC micros for you!!!"

Is there a way to correct it? i mean some form of protection circuits to save the PIC...?

Let my experience be a lesson for all PIC users....!

BEAMer

Soeren · « **Reply #1 on:** February 28, 2009, 12:14:40 PM »

Hi,

If you shunt the Vdd and Vss pins, no harm should come to the controller, as it just sees 0V (unless you have a semi-large inductance in the power supply, that could spike when the shunt is removed).

Your power supply, however, is an entirely different matter.

BEAMer · « **Reply #2 on:** March 01, 2009, 02:27:09 AM »

oh..... but my controllers are not working now.

actually i have an LED in the 7805 5 volt regulator board. when i use it to power my blown PICs, they glow dim.... when i measured the voltage, its around 3.5V instead of 5V.
when i remove the PIC, the LED glows bright as usual. what could be the reason....?

BEAMer

TrickyNekro · « **Reply #3 on:** March 01, 2009, 04:53:35 AM »

Darn.... Use AVR!!!!
They even survive a 3K volts spark discharge at the supply!!!

Tested!!!!!!

Admin · « **Reply #4 on:** March 03, 2009, 06:03:05 AM »

Quote from: TrickyNekro on March 01, 2009, 04:53:35 AM

Darn.... Use AVR!!!!
They even survive a 3K volts spark discharge at the supply!!! Tested!!!!!!

3k volts?! static electricity, or are you making a robot with freakin lasers on its head?

BEAMer, are you sure it isn't a different part of your circuit causing the problem?

paulstreats · « **Reply #5 on:** March 03, 2009, 06:47:02 AM »

I dont want to be rude, but are you sure that youre connecting +5v and GND to the correct terminals in the PIC's? I cant imagine a short that causes such a power drop withour you seeing any glowing parts or any smoke coming from your circuit or your PIC - If this happened I'm sure you would have mentioned it in the post above.

Could it be that when you shorted the terminals, rather than damage the pic, it fused the strips together on the bottom of the bread board? (is this possible?)

I agree with soeren, i cant see the pics being damaged like this (mine have survived more accidental abuse).

Is there anything else but the PIC in the circuit youre testing

BEAMer · « **Reply #6 on:** March 04, 2009, 07:40:09 AM »

yeah i use a ZIF socket board which has a clock and pinouts for ports... its a fabricated PCB so nothing can go wrong with the connection. moreover i have been using it for many years..

when i was checking the voltage at the power and the ground i just moved the multimeter probe and i accidentally touched both the vdd and gnd pins (these pins are close to each other). and thats it, there was a small spark and the PIC stopped working...

I even tried programming it again, but the programmer is not recognizing the PIC (my programmer has an autodetect feature)...

BEAMer

BEAMer · « **Reply #7 on:** March 04, 2009, 07:42:01 AM »

hi TrickyNekro,
i have not used an AVR till now.....

i am kinda comfortable with the PIC

BEAMer

rack2020 · « **Reply #8 on:** March 12, 2009, 08:46:48 AM »

well, i generally solder my circuits on boards. so first i will fix a 40 pin base for the micro on the board and solder all the lines. then i will use mu multimeter to check continuity. that will produce a beep sound whenever there is a short...

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