Your "padding" resistors are only 1K, not 10K as shown in the diagram. You'll get a better result using the 10K resistors.

 

Your "padding" resistors are only 1K, not 10K as shown in the diagram. You'll get a better result using the 10K resistors.

How so? "Better" depends on the OP's requirements and, in any case, his circuit doesn't work and mine does.

1K fixed resistors on the ends of the pot will allow him to get very close to 0% and 100% duty cycle without hurting the 555, which may be just what he's looking for.

 

How so?

My comment was directed to the TS. Without the 10K padding resistors, much of the pot's rotation will be wasted in dead zones.

This may all be moot. I thought I read his resistors as brown-black-red (1K) but the red band might be orange (10K) as intended.

 

Anyway... I'm not satisfied with the result: yes, it's true, now i can go from no light to about full brightness.... but all the brightness change is concentrated in the first half of potentiometer. Even with a small rotation i get half of the brightness and it's very hard to set a desired low brightness setup.

You might also try tweaking your padding resistors to ensure you're getting 1/3 and 2/3 Vcc at the ends of your pot's travel.

 

My comment was directed to the TS. Without the 10K padding resistors, much of the pot's rotation will be wasted in dead zones.

Which dead zones are you talking about?


This may all be moot. I thought I read his resistors as brown-black-red (1K) but the red band might be orange (10K) as intended.

As intended? So you'd damn us all by your inability to distinguish between red and orange?

 

"his circuit doesn't work and mine does."

The two circuits are identical electrically in that one side of the pot is used to charge the capacitor and another to discharge it. The diodes act to steer the charge and discharge current.

We don't know why the ops circuit didn't work but we know for sure it is not due to the schematic.

 

As intended? So you'd damn us all by your inability to distinguish between red and orange?

I don't understand the attitude. I was merely pointing out a potential source of his problem based on his photos. Many have built that circuit with good results and I'm sure our TS can get good results also.

 

"his circuit doesn't work and mine does."

The two circuits are identical electrically in that one side of the pot is used to charge the capacitor and another to discharge it. The diodes act to steer the charge and discharge current.

We don't know why the ops circuit didn't work but we know for sure it is not due to the schematic.

The two circuits are _not_ identical.
Mine works, Luca's doesn't.

 

The two circuits are _not_ identical.
Mine works, Luca's doesn't.

Saying the same thing over and over doesn't really help you defend your position.

Laying out facts and reason with sound logic does.

 

Saying the same thing over and over doesn't really help you defend your position.

Laying out facts and reason with sound logic does.

Yup, you're right; I overreacted. Sorry about that...

I just finished simulating Luca's circuit and mine side-by-side, and they function identically. In fact, Luca's is a little better than mine because it uses one less resistor.

Matter of fact, if he changes that 50k pot to 100k he ought to get close to 1% duty cycle with the wiper at one end of the element and close to 99% with the wiper at the other end.