555 problem - can't get wider pulse

[blapcb]

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)

 

[keith1200rs]

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

Keith.

and no resistor in series with the capacitor.

 

[karesz]

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.

 

[blapcb]

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......

 

[GrandAlf]

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.

 

[karesz]

Hi,
@Grandalf
I didnt others said...
@blapcb
Grandalf ha sright, you will find dozen of sides over circuits (often the same) www.kpsec.freeuk.com/555timer.htm
K

 

[pauloynski]

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

 

[blapcb]

Thanks guys very much for all your help. I guess I goofed up such a simple thing.... but now I understand. Thanks again.