Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

circuit help

Status
Not open for further replies.
please tell me whch transister would be able to deliver the amount of current required in my project.
You don't show which part of the world you are in. I am in Canada where I use American 2Nxxxx transistors. People in Europe use BCxxx transistors. People in the Orient use 2SCxxxx transistors.

I would drive the 9 LEDs from the collector of a 2N4401 transistor. Each blue LED needs a 100 ohm resistor in series from the +5V supply and the base of the transistor should have a 330 ohm resistor in series from the output pin of the microcontroller.
 
@Audioguru
Thanks alot for that kind of help. i live in Pakistan.And all these series are available here. 2nxxxx,BCxxx are used by me once before. i will try to configure this and tell you the result.But you did not tell me the emitter of the transistor is directly connected with ground.?
and what is the resistance of the LED when forward bias? i check it (when is off) By putting positive prob on anode and negavie prob on cathod.


and thanks once again.
 
Last edited:
The emitter of an NPN transistor (use a BC337) connects to ground. Each LED is in series with a current-limiting resistor and connects from the collector to +5V.
The base has a series current-limiting resistor and is turned on when its base resistor goes positive.
 
Hello Audioguru.
i used 2N4401 transistor and none of the 9 LEDs are lighting at all. should i change the transistor now? should i use Bc337?
and the second problem, i noticed and wanted to tell you that the tuning the remote till the receiver receives the signal is very difficult. because suddenly the receiver receives the signal and then after a second it doesn't. i am tried doing tuning again and agian. check the circuit and suggest me an idea that through which i just tune it once and use theremote control.

Thanks
 
Last edited:
Hello Audioguru.
i used 2N4401 transistor and none of the 9 LEDs are lighting at all.
You didn't post a schematic showing how you connected the transistor (maybe it is connected backwards) and which base resistor value so I don't know what is wrong.

the tuning the remote till the receiver receives the signal is very difficult. because suddenly the receiver receives the signal and then after a second it doesn't. i am tried doing tuning again and agian. check the circuit and suggest me an idea that through which i just tune it once and use theremote control.
I don't see which IR transmitter circuit you are using. Usually an IR transmitter is not tuned because it should have a fixed frequency.
 
Last edited:
I am attaching the REceiving module and the 9 LEDs circuit which i connected.
and the circuit of whole project and remote is on page 1 of this fourm.
 

Attachments

  • circuit.GIF
    circuit.GIF
    67.9 KB · Views: 151
  • DSC00189.GIF
    DSC00189.GIF
    732.5 KB · Views: 133
Now your blue LEDs will have a current of about 16mA each and will be bright if they are turned on continuously.
 
But they are not lighting at all !!!
When the base of the 2N4401 transistor goes to a logic high voltage then the transistor will turn on and light all 9 LEDs.
Maybe the pins of the transistor are connected wrong.
Maybe the pins of the LEDs are connected backwards.
Maybe the input to the base of the transistor does not go to a logic high voltage.
 
Hello,
i have checked all things. i have disconnected the base resistor from the base of the transistor and checked the votages at the end of the resistor, the voltage is 0. and while the base of the transistor is not connected to anything, i shorted the base and collector of the transistor then all the 9 LEDs are glowing till base-collector is shorted. mean LEDs are fine and transistor is also fine. But the output from the microcontroller is always low (this seems to me). But when i first time turned the analog mode on, the 9 LEDs were glowing at that time very lightly. But now They are not glowing. please check it? i have uploaded all the things on page 1 of this forum.

Thanks a lot
 
Last edited:
If you short the base of the transistor to its collector without a series current-limiting resistor then you risk blowing up the transistor because then its base current will be extremely high.

The program for the microcontroller tells it to turn on the output for the blue LEDs or not. I don't know the program.

EDIT: corrected.
 
Last edited:
i shorted the base and the collector of the transistor only once(NOT Base-emetter) to check whether all the LEDs are OK or not. and every LED is lighting till the base and the collector is shorted.and the program file is on page 1 of this forum. please check that. please
 
Last edited:
A transistor can blow up in one instant. You did not limit the base current when you shorted the base to the collector so you are lucky that it still works. Instead you should connect the base resistor to the supply voltage of the microcontroller then the resistor limits the base current.
I have never programmed a microcontroller so I don't know what yours is supposed to be doing.
 
ok. tell me what should i do now? I beleive that the program is fine something is wrong besides program. what should i check? because the 9 LEDs were lighting few days ago very lightly before you told me to connect the transistor. But now no voltage on the output pin of Microcontroller for 9 LEDs. what should i do?
 
Maybe you burnt out the output circuit of the microcontroller by overloading it by trying to directly drive the very high current for the LEDs.
Maybe the pins of the transistor are connected backwards. You did not test the transistor correctly so maybe it is also burnt out.
 
i have replaced the icrocontroller today and the output of this circuit is zero to only 9 LEDs. every thing except this is working fine in digital mode and in analog mode.
How to test the transistor.?
 
i have replaced the icrocontroller today and the output of this circuit is zero to only 9 LEDs.
The output from the microcontroller should go to a logic high voltage (+4.5V to +5V if its supply is +5V) to turn on the transistor.

How to test the transistor?
I told you already. Disconnect the 330 ohm base resistor from the microcontroller and connect it to +5V to turn on the transistor which will light up the blue LEDs brightly.
 
Last edited:
when i am connecting a 330 ohm resistor in series from +5v to the base of the transistor, the 9 LEDs are all glowing. mean the LEDs are working fine and the trasistor is also OK. so result is, the problem is in the program. am i right? or is there anything remaining before i come to the result.?
 
Hey! i tried by changing the bit for the 9 LEDs and thank God the 9 LEDs are glowing now :) But very light. now tell me how increase their intensity? this time the 9 LEDs are glowing through transistor.
 
If the output from the microcontroller turns on and off at a frequency that you do not see and with narrow pulses then the LEDs are dimmed. If the pulses are wide or if the output is continuously high then the LEDs will be bright.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top