how to determine if my pic16f877a ic is broken??

Discussion in 'General Electronics Chat' started by yuanshikai, Nov 5, 2011.

1. yuanshikai Thread Starter Member

Sep 17, 2011
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0
how do I test if my ic is broken? and what connections can cause my pic to be broken?

Last edited: Nov 5, 2011
2. nigelwright7557 AAC Fanatic!

May 10, 2008
527
74
Write a very simple program, for it that switches an i/o port high and low.

Over voltage into the chip will kill it.

3. yuanshikai Thread Starter Member

Sep 17, 2011
49
0
isn't the output on a pin of a port always 5V or 0V when the supply is 5V? my output pins read something like 0.5V..

4. MrChips Moderator

Oct 2, 2009
16,866
5,178
If the pin is not configured as output, the voltage on the pin can be anything.
If the pin is an output, 0.5V may not be terribly wrong. You have to check the specs for
$V_O_L$.

Do what post #2 says. Try to toggle an output pin.

5. yuanshikai Thread Starter Member

Sep 17, 2011
49
0
it seems my ic really is broken, but what could have caused this this in my circuit?

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6. MrChips Moderator

Oct 2, 2009
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I cannot read the values of R1 and R2. I would replace both with a 5V regulator such as a 7805.

7. yuanshikai Thread Starter Member

Sep 17, 2011
49
0
this is supposed to be a voltmeter and the voltage to be tested was the 9V source. R2 is 2Mohms and R1 is 100kohms..

8. MrChips Moderator

Oct 2, 2009
16,866
5,178
Sorry, I thought that was your 5V supply.

9. yuanshikai Thread Starter Member

Sep 17, 2011
49
0
it's not shown in the image but my voltage supply for the pic is 5V btw.

10. ErnieM AAC Fanatic!

Apr 24, 2011
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I don't see any limiting resistors between the PIC outputs driving the 7 segment displays, meaning you have a very large current into each LED. That will pop the PIC in short order.

Just before it blows the output pins will have the LED on voltage at them, depending on the display something like 1.5 volts.

11. yuanshikai Thread Starter Member

Sep 17, 2011
49
0
damn.. thanks alot.. what value should the limiting resistors be..

12. spinnaker AAC Fanatic!

Oct 29, 2009
6,644
2,928
It will depend on the forward voltage of your LEDs, your supply and the amount of current the LED and PIC can handle.

http://blog.datasingularity.com/?p=243