soldering mistakes in pic16f877a

[rangerskm]

i soldered my pic16f877a ic in board,first 2 ic s were burned out ,finally i soldered 3rd one .its working but the voltage i got from the tx pin is 3v.the input to the pic is 5v.

my questions are
1) do we have to give 2 vdd and vss in PIC ?if i do what happens?
2) how to check the correct working of oscillator and capacitors.
3) why its showing 3v in tx pin ?
4) how to check max232 ic?

 

[mathespbe]

1. Yes you need to connect those 2 Vdd and Vss
2. To check the osscillator the only way is CRO. Simply write a code to toggle a pin. If it works the OSC is working fine...
3. You may need external pull up for Tx pin...
4. Simply loop back your Tx OUT and Rx IN pins and check it in the hyper terminal itself...

 

[rangerskm]

how we connect external pull up for tx pin ?can u explain?

 

[mathespbe]

pull up is just to make any voltage level more than 0.7 range into Vcc...
It's just a transistor pulling up...

 

[pasicr]

If you use DIP version of 877 use DIP socket, do not solder PIC mcu directly...
regards

 

[rangerskm]

1)why we are using capacitors along with crystal ?do the absence of capacitor affect the oscillator frequency ?
2)whats the use of brown out enable bit ?? can you say any method to prevent ic from damaging in soldering ?


i am new to soldering so i am in need of your help,thanking you in advance..

 

[wp100]

Hi,

Have a read here as to use function of the crystals capacitors.
https://www.adafruit.com/blog/2012/01/24/choosing-the-right-crystal-and-caps-for-your-design/

The Brown Out is a voltage level that the chip will sense and cause a shut down/reset until the voltage is restored.
General comment is that you are better turning that function OFF

Soldering,there are many online soldering guides / videos to look at.
https://www.youtube.com/watch?v=fYz5nIHH0iY

Professional pcbs have whats called a Solder Mask, a protective substance coating the non solderable areas that makes it so much easier.

For diy board you just need to learn to be careful, using the right sized iron / tip /temperature and some practice.

As Pasicr said, for Pics its best to use IC sockets, but if you do want to solder them in the use the three second rule, as you solder each pin count one two ,thee seconds, if the joint is not made, stop, allow it to cool before attempting again.