something confusing me with LED

Status
Not open for further replies.
B

baby_1

Advanced Member level 1
Joined
Dec 3, 2010
Messages
415
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Activity points
4,277
Hello
the 120 resistor it is connected to a pin of micro (pic18f452) when i set it high( set 5 volt at the resistor terminal) it works fine

but when i changed the 1kohm situation at the collector of bdx53 led won't work!!!!!


i tested it by BC337 and BDx53 and two led but it doesn't work at the second circuit.why?!!!!
 

You've obviously hooked something up wrong. It makes no difference which way you do this.
 

Measure from both ends of R2 and D1 and the Q2 collector. You should have 9 V, ~1.6 V, ~1.6 V, 0V and 0V. This won't be the case though, because you've connected something wrong.
 

Hello Sloth
VBE=2
V(resistor 120ohm)=3.1 ~ 3.2
VCE~=1.5
 

If the LED was ever put in reverse the 8V reverse voltage would damage the junction and short it out. Vr=5V max.
What is the LED diode drop now?
 

Hi,

VCE seems high. How about the R2 and D1 ends? I think something is not connected there.
 

Vbe is way high. Should be about 0.6V. Something bad happened to your components.
 

Vbe is way high. Should be about 0.6V. Something bad happened to your components.
Click to expand...
BDX53 is a darlington. Vbe of 1.2 to 1.4 is O.K.
 


did you do both simulation & actual testing?
 

No need. He already got it to work in a similar arrangement. I think he killed a part.
 

Joeisi said:
No need. He already got it to work in a similar arrangement. I think he killed a part.
Click to expand...

ah i see.
to add, initial study must be done to ensure proper connections and setup.
 

LED's act as load .then what is the collector current ?
LED's Current ?
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…