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How 2 trigger a monostable

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another guy

New Member
This is probly very simple, but can any1 tell me how to trigger a monostable electronicly without using a push button.i need a circuit that gives a single pulse 2 trigger the monostable.any help?thanx
 

jimlovell777

New Member
What's the trigger for the event? You can trigger a monostable using a switch, other logic... any number of things. Being more specific and descriptive will greatly improve the responses to your question.
 
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another guy

New Member
Basically i wana trigger it 2 turn on a motor for 10
sec..the problem tht i have is jst 2 give the trigger input a pulse without using a push button.so i just need a circuit that can give 1 pulse when activated 2 trigger the timer.i tried a inverter logic gate to trigger the 555? but the timer stayed on and didnt go off.is it more clearer nw?thanx
 

ericgibbs

Well-Known Member
Most Helpful Member
Basically i wana trigger it 2 turn on a motor for 10
sec..the problem tht i have is jst 2 give the trigger input a pulse without using a push button.so i just need a circuit that can give 1 pulse when activated 2 trigger the timer.i tried a inverter logic gate to trigger the 555? but the timer stayed on and didnt go off.is it more clearer nw?thanx

hi,
Please post the circuit diagram of the existing 555 monostable, showing how you have the trigger connected.:)
 

another guy

New Member
I dnt have the resources of scanning rite now as im using my mobile 2 place threads but basically pin 2 on the 555 is connected 2 ground and the not gate is joint 2 it,hope u understand what im sayin.thanx
 

ericgibbs

Well-Known Member
Most Helpful Member
I dnt have the resources of scanning rite now as im using my mobile 2 place threads but basically pin 2 on the 555 is connected 2 ground and the not gate is joint 2 it,hope u understand what im sayin.thanx

ok,
Dont directly couple the trigger source to the 555 trggger input.!

Use a 10nF or 22nf capacitor in series with the trigger, look at this image.
 

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sheldonstv

New Member
Try this schematic which includes the necessary switch debounce to ensure your 555 is triggered correctly.........do not be scared of it
 

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  • SWITCH DEBOUNCE 4 NE555.pdf
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ericgibbs

Well-Known Member
Most Helpful Member
Try this schematic which includes the necessary switch debounce to ensure your 555 is triggered correctly.........do not be scared of it

hi,
Again, the OP is using a Push button, which is most likely a n/o or n/c set of contacts, not a change over switch.:)

So your circuit is not suitable for a simple n/o or n/c push button, I think you should make this clear on you circuit.
For a change over contact set its fine.
 
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MrDEB

Well-Known Member
here is a N/o push button trigger input

should work if I read your circuit explanation correctly.
this is a 556 so pin out is slightly different.
the (#) indicate pins on a 555
 

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  • 556 flasher.PNG
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sheldonstv

New Member
the circuit here(u2a,u2b,u2c,u2d)is a switch debounce circuit also which can be used to trigger your 555,as long as you add the capacitor,diode and additional resistor so you can edge trigger your 555........
 

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  • CCTV SWITCHER.pdf
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