555 + 4017 + high bright led driver

[audioguru]

With the series base resistor of the transistor R3 connected to +9V and the LED blinks then the +9V supply must be bouncing up and down probably because your 9V battery is dead, or the ground wiring is intermittent. Breadboards always have intermittent wiring.

Oh. You have one LED directly connected to an output of the CD4017 without a current-limiting resistor. Then the CD4017 is straining at the high current.
Do you have anything else connected to the output of the 555 that draws a high current like maybe a speaker?

 

[alex69]

Here I am.
Ok audioguru, I don't use battery. Only DC power supply 0-5A 0-30V.
No other output connected to 555 (it's only driving 4017)

"...or the ground wiring is intermittent. Breadboards always have intermittent wiring"
I'm going to think that's the problem. Next days I'll try to build a pcb.
If someone has another ideas...

 

[alex69]

I've realized circuit from breadboard to a solid base but the problem is still present.
Tomorrow I'll try to replace CD4017

 

[alex69]

Found the solution.
Connecting a capacitor between base of BC547 and gnd, the feebly light disappears.
And now... Why ?

 

[audioguru]

Found the solution.
Connecting a capacitor between base of BC547 and gnd, the feebly light disappears.
And now... Why ?

The the signal at the base of the transistor is causing the transistor and LED to turn on when they shouldn't. The signal comes from the CD4017 which is probably defective.

 

[alex69]

thank you. tomorrow I'll replace it.
see you tomorrow.

 

[alex69]

Hi audioguru.
I've replaced the CD4017 and now all is ok. All leds flash works fine (when output is UP and also when is DOWN).
Thank you.

 

[audioguru]

I have used tens of thousands of name-brand ICs and never had a bad one. Because I never bought junk on EBay nor RadioShack.

 

[alex69]

Me too. It was an old IC that I forgot in a far black hole of my toolbox.
Think I damage it in other experiments.
Ok. Thank you.

 

[alex69]

Another help to understand.
I've found some scheme using ULN2003 (like someone suggested me in this thread) that replace long number of BC547.

These are my questions:
1 - In some scheme connection between CD4017-output and ULM2003-input are directly
and in some others is used a res. It's the same thing?
2 - pin9? what I use for?
3 - The input signal from CD4017 is used only to activate base of transistor inside
ULM2003 so collector and emitter do the rest. Right?

Thank in advance. Alex

PS: My leds are always 3,4v - 50mA - High Bright

 

[audioguru]

1 - In some scheme connection between CD4017-output and ULM2003-input are directly
and in some others is used a res. It's the same thing?

If you looked at the datasheet for the ULN2003 then it answers your questions.
Its built-in input resistors are designed for 5V logic but yours is 9V. You can add a series resistor to each input or use a ULN2004 that has higher value input resistors.

2 - pin9? what I use for?

It is used so that its free-wheeling diodes arrest the high voltage spike created when an inductive load (relay, solenoid or motor) is turned off. Your LEDs are not inductances and you don't need pin 9 so don't connect it to anything.

3 - The input signal from CD4017 is used only to activate base of transistor inside ULM2003 so collector and emitter do the rest. Right?

Correct.

 

[amitpj]

he buddy i have seen ur video and by seeing that one thing i got in my mind ....
that is u change transistor and check i thinks some where in between 4017 and led ...when current goes high a current is storing and when current goes low that current is discharging ... what i mean is some where capacitor action is taking place so .... once again u remove wire from breadboard and re connect the circuit but this time u see that to eliminate wire ( dont use more wire in breadboard because of that some trouble is taking place ) ..... see it and reply me

 

[alex69]

Thank you for your interest but I've just find solution.
It was a defective, old, used and re-used pic.
Replacing it the feebly light disappare and the old 4017... to the trash.

PS: I've tried things you said but nothing. Led still flash feebly.

 

[alex69]

ok audioguru. thanks. I'll study it and soon post a new scheme.
Alex

 

[alex69]

OK. Done. ULN2003 works very fine.
Unfortunately it has only 7 input/output. Better is ULN2803 or 2804 which as 8 input/output (but not 10!).
So, another simple scheme done and understand how to use it.
Thanks to all.
Alex

 

[MrDEB]

Sorry my bad it was supposed to be the ULN2803 to begin with. I didn't know there was a 2003?
I need to quit relying on memory.

 

[alex69]

Oh yes. Also me has some black hole an my mind but, because of the aid of this group, I can regain my sanity!
You can take a look here:
http://www.datasheetcatalog.org/datasheets/105/366825_DS.pdf
http://www.datasheetcatalog.org/datasheet2/f/0c6x6a46ig46qlxf3j2qsaii8o3y.pdf
Thank to all.
Alex