TS 555 CN 50 duty cycle problem

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boylesg

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Can any body tell me what I have done wrong with this circuit - I just cant see it.

I am trying to implement this circuit.



Here it is on my bread board. The transistor circuit is not connected atm. R1 = 100k as per above schematic. R2 is a 10k trimpot. C1 = 10nF
But I am getting a steady 5V out of pin 3 - no oscillation whatever.

 
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Hi,

what does the red wire on pin5 do? It´s not according the schematic.

Klaus
 

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Put a 10uF cap from pin 8 to pin1 for starters ....
--- Updated ---

make sure pin 4 goes to pin 8 ...
 

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More than once I've hooked together a 555 pulse generator (hardware) and I saw constant supply voltage on the oscilloscope. When in truth it was about 99 percent duty cycle! Low state lasted so briefly it didn't appear onscreen at first until I adjusted a few dials.

By applying various volt levels to pin 5 (Ctl pin), I change duty cycle. The 555 is constructed to do that. Yet most designs just put a capacitor to ground.
 

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