can't get 555 cicuits working...

[Hal]

I went to the Rat Shack, and picked up a 555 and the box of assorted LDR's to build Ansil's tremolo...but, no matter what I do, following both his schematic, or a different one I have, I can't get my LED to blink!  It only glows dimly.  Lowering the resistance between pins 6 and 7 brightens the LED, but thats it.  

I'm counting pin one where I see a dot, and around, so to the right of that is 2, 3, 4, and 5 is right across from 4, , then back to the left for 6,7,8...Right?

How possible is it to blow one of these?  Thanks.

[Nasse]

just a quick quess but cheks your cap and res values, maybe ten times too little cap and the led flickers faster than your eye can see...

[blabj]

hmmm, correct me if im wrong, but in a school electronics project, were making a dual blinking led timer, and for the l.e.ds we used "blinking" leds. they just have a blck dot in the middle, and they work ( just a thought)
and the i.c's pinout is left side 1-4 right 4-8

[smoguzbenjamin]

Code Select Expand

1o--8
2---7
3---6
4---5


That's how all IC pins are counted.

[Hal]

yea, I counted right then...

I'm using a 3.3 uf electro, tried pos and neg to ground.  Also tried another in paralell with that, different polarity.  Instead of the pot and 1k in series, I'm using a 43k resistor.  the 10k is the same.  I'm using 270 ohm resistor to limit current before the LED.

[Ansil]

yea, I counted right then...

I'm using a 3.3 uf electro, tried pos and neg to ground.  Also tried another in paralell with that, different polarity.  Instead of the pot and 1k in series, I'm using a 43k resistor.  the 10k is the same.  I'm using 270 ohm resistor to limit current before the LED.

with the 3.3uf it will blink faster than the the intended 4.7uf but htat shouldn't be too much of an issue.  you will probaly need to use a 1k as i prescribed for the limit resistor of the led, as this is the first value i grabed, i had an offboard led and resistor and wires already wired up for a test light i forgot about the resistor and i built the other values around the value that the led was putting out. with the 1k resistor.  since i am limiting more current to the led is another reason you might not see yorus flash.

what is the dark value of your ldr?  mine was 500 k when dark as i could get it without mounting in a black plastic tube.

what led do you have.  mine is a 5mm green.
the more resistance you ahve in the circuit ie where you have a 43k will equal the slower flashing.  it will flash faster with less resistance.



editedafter further reading on your dilema here i think you may have a bad cap.  i could be wrong but usually when i have screwed up days i sometiems forget the cap in this type of circuit and then i am kickin myself in the but when i cant'  figure otu why it doesnt' flash.. i know you said you parralleled another cap with it, but try taking that one out, and replacing with another one.  try puting in a 1uf cap. i wll double check maybe i was usign a .47uf as i have one like that that looks similar, but i am alomst positive that it was the 4.7uf, but i will look again. hmm wait i am sure now, cause a few others have used the schematic and gotten it to work so i am puzzled,  are you using a cmos 555 that shouldnt' make a difference but it could maybe i am not using a cmos one.

edited again..ok i went and built it.. it is correct as posted sorry i don't know what else to say

[petemoore]

find the link or just type NTE in your adress bar and read how to enter the part # and then try the html on the NTE part...brings up the data sheet at the bottom of that is the pinout on the 386...er NTE [823 is it?]...well type in lm386 in the cross reference window and it'll tell you that too..

[Ansil]

find the link or just type NTE in your adress bar and read how to enter the part # and then try the html on the NTE part...brings up the data sheet at the bottom of that is the pinout on the 386...er NTE [823 is it?]...well type in lm386 in the cross reference window and it'll tell you that too..

what..  i thought we were talking about the 555 timer here

[Hal]

yes, ansil, we are...

I found _another_ scematic, the iguanalabs one, and followed it, and it worked (pretty) well.  Most of the values are higher...I'm using a 47 uF cap now....

Its still working intermittently, though (I love that word).  Could be a short somewhere or something...Pain in the butt.  This is my first experiance using 7 out of 8 pins of an IC on a breadboard....gets _messy_


Thanks for all your help, though.

[Ansil]

no prob bob

[smoguzbenjamin]

:mrgreen: Breadboards are fun with ICs! :mrgreen: I like when my breadboard is full of crap and people go "wow that looks complicated/important" while it isn't really