voltage drop

blessbernie

New Member

• Jul 1, 2016

• #1

after putting my PIC in d socket, d voltage from the 7805 drops to abt 1.4v. wat could be the cause. urgent plz. it's jst a simple temperature sensor circuit

 

crutschow

Well-Known Member

Most Helpful Member

• Jul 1, 2016

• #2

Something is drawing more current than the supply can deliver.

 

blessbernie

New Member

• Jul 1, 2016

• #3

hw can I figure that out.

 

alec_t

Well-Known Member

Most Helpful Member

• Jul 1, 2016

• #4

Carefully examine your circuit to see if there are any stray wire strands or solder splashes causing a short-circuit somewhere.
Double-check the circuit you have built, to ensure it's consistent with the schematic.

 

S

spec

Well-Known Member

Most Helpful Member

• Jul 1, 2016

• #5

Or the 7805 could be misbehaving- perhaps oscillating. Have you got any decoupling capacitors across the supply lines. If not try 100nF.

spec

 

blessbernie

New Member

• Jul 1, 2016

• #6

tnx alot Alec_t and spec

 

ronsimpson

Well-Known Member

Most Helpful Member

• Jul 1, 2016

• #7

blessbernie said:

d voltage from the 7805 drops to abt 1.4v

Click to expand...

What is the input voltage at the 7805?

 

MikeMl

Well-Known Member

Most Helpful Member

• Jul 1, 2016

• #8

Read Post #14 in this recent forum thread It deals with not having sufficient voltage upstream of the regulator...

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Jul 2, 2016

• #9

I would strongly suspect you've put the chip in the wrong way round!

This would produce exactly what you're getting - the chip will also be getting red hot, so don't touch it.