555 problem - can't get wider pulse

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blapcb

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Hi. I have the attached circuit which takes a trigger signal and outputs a nice square pulse. Problem is, it is only 3 micro seconds wide. I am trying to make it wider but can't seem to do so (by changing the component values). What am I missing? Thanks.

(Please note that though it does not show it, VCC and RST are pulled high to VCC)
 

I think a resistor between DIS/THRS and Vcc would be a good idea!

Keith.

and no resistor in series with the capacitor.
 

Hi,
I think; you must be happy if the "discharge transistor" isnt dead, than hese collector is on pin 7_yet directly on Vcc (& emitter is on GND)! :-(
In practicum I would take higher values for the timing resistor (can be max upto 10MOhm) and smaller capacitancece->smaller volumen_as possible... I think at some 100KOhm nice for allday business with the needed 100nF or so.
K.
 


Hey thanks a lot my friend, but.... can you explain that and perhaps add a circuit? Sorry I did not understand, other than pin 7 should not be connected directly to Vcc......
 

Keith1200rs is correct about connections. There are masses of 555 circuits if you Google. You will be able to find how to calculate the timing period also.
 

Here you can find circuits and a calculator. **broken link removed** There are dozens of sites like this one, just google a while.
 

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