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555 doesnt work :(
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555 doesnt work :(

by dragonuv on Wed Feb 25, 2009 7:39 pm

ive tried connected everything with the right values of resistors and capacitors but it still doesnt work.
anything i should check with the multimeter?
picture:
http://img150.imageshack.us/my.php?image=img1502.jpg

p.s: about the 4 resistors with the same value on the right side of the breadboard, those are 130 ohms resistors, 2 in serial and 2 in parallel (together 325 ohm)
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Re: 555 doesnt work :(

by magician13134 on Wed Feb 25, 2009 8:13 pm

What kind of 555 are you using? If I remember correctly, only a CMOS 555 would work with 5V, try a 9V battery.
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Re: 555 doesnt work :(

by zener on Wed Feb 25, 2009 11:59 pm

A regular 555 should work at 5V. For example the NE555 is spec'd down to 4.5V. 555's can be little tricky if you don't have a scope to check out what it is doing. It is kind of a hokey device actually. If your RC timing is off then it will seem to do nothing. It takes some trial and error sometimes. You might be able to get somewhere using a voltmeter.

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Re: 555 doesnt work :(

by dragonuv on Thu Feb 26, 2009 10:03 am

which pins of the 555 do i need to check with the multimeter?
and btw its an NE555
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Re: 555 doesnt work :(

by dragonuv on Thu Feb 26, 2009 1:58 pm

it works now, but i dont know why. i was hoping you people could help me.
whenver i touched the blue capacitor ive noticed slight pulses with the led, i thought it must be something with grounding so instead of the capacitor i took a wire and instead of its right leg ive connected it with -. it didnt work and then i connected it with the +. so now it works great. but how so?

thanks.
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Re: 555 doesnt work :(

by zener on Thu Feb 26, 2009 8:14 pm

The 555 is a voltage divider feeding 2 comparators that go into a flip-flop and then with a logic output and an open collector output. It is a lesson in several electronics concepts such as voltage dividers, comparators, RC time constants, flip flops and open collector outputs. You will get more out of it if you have a scope to see what is going on. There are about a million ways to wire one up since it sort of a grab bag of parts in a chip, not a specific function chip as is commonly thought.

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Please be positive and constructive with your questions and comments.