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NE555

Ö

ÖRJAN LOMAN

Jan 1, 1970
0
Hello!
I want to build a monostabile oscillator which is
triggered by a signal to the triggerinput. I want just
one and only one puls when the trigger-input connencts
to -. I have tried to get just one puls, but when the
trigger-input is disconnected from - another puls is
generated. I don´t want that to happen. Please help me.
Thanks /Orjan
 
J

Jim Backus

Jan 1, 1970
0
Hello!
I want to build a monostabile oscillator which is
triggered by a signal to the triggerinput. I want just
one and only one puls when the trigger-input connencts
to -. I have tried to get just one puls, but when the
trigger-input is disconnected from - another puls is
generated. I don´t want that to happen. Please help me.
Thanks /Orjan

It's a long time since I used a 555 but IIRC it shouldn't do that. You
talk about disconnecting the trigger input - is it possible that you
are accidentally producing another trigger from spurious edges as yu
disconnect?


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M

manifold_1

Jan 1, 1970
0
The 555 requires a positive trigger pulse right? It may be that when
you disconnect the trigger source, which is negative, the trigger is
going positive and generating a trigger pulse.

Try putting a diode on the triger input to keep it form going
negative. Also add a pull down resistor to keep it low if
disconnected.
 
T

Terry Pinnell

Jan 1, 1970
0
Tease!

No, it needs a -ve going trigger. Not necessarily even a pulse - a
negative DC voltage will continue to 'trigger' the mono.
 
J

John Fields

Jan 1, 1970
0
Tease!

No, it needs a -ve going trigger. Not necessarily even a pulse - a
negative DC voltage will continue to 'trigger' the mono.
 
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