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single pulse generator

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Hi, I have looked at other posts, a 555 timer circ in monostable mode comes up. what I am looking for is to push a button and get a single pulse 500ms more or less, It is not that critical less may be better. so every time you push button you get one pulse. is there an easy way to do it with differnt components. the less the better. debounce and square wave is not critical just a brief positive pulse of 5v to reset circuit. Thanks, Steve.. I have a few ne555's to use, I have been having a hard time setting it Up could someone post the values for a 500 ms pulse and a schematic if possible, the only result I am getting is providing a pulse when going from 1 to 0 state. I need 1 pulse when going to 1. any help appreciated!!!!

Also have seen a cd4001 used It looks pretty basic, but, again I am not sure how to figure values? any thoughts on either or?
 
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edeca

Active Member
The monostable on this page is documented very well: http://www.kpsec.freeuk.com/555timer.htm#monostable

You use the RC "timer" to set the pulse length and the 555 trigger input is used to enable the "pulse".

Once you've got the basic circuit working there are a few ways to hook this up. For example if the switch is held down what should happen? Do you expect the pulse to be elongated, or to end after 500ms? There are lots of possibilities with the 555.
 
If the switch is held down nothing happens except the immediate 250-500ms pulse. I would like positive pulse upon pushing button and go back to 0 around 250ms- 500 ms later... I see the diagram shows a reset as well as a trigger, every shematic I have seen is different? I would like for it to reset itself after button is released. I only have .1uf ceramic caps I think.... most diagrams show a .01uf. I dont understand the formula either? there are different ways to rate the capacitor is it in uf? and multiply it by what resistor number? is 1K going to be 1000? an explanation of that may help some as well?
 
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jainysaini

New Member
I need help designing a 3 single pulse generator. Each single pulse generator is connected to the gate of a mosfet. These pulse generator will turn on 2 mosfets together then turn on the 3rd mosfet when the 2nd mosfet turns off. the 2nd mosfet has a longer turn on time. See attached file for a detailed explanation
[MODNOTE]Deleted link[/MODNOTE]
 
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eTech

Well-Known Member
Hi, I have looked at other posts, a 555 timer circ in monostable mode comes up. what I am looking for is to push a button and get a single pulse 500ms more or less, It is not that critical less may be better. so every time you push button you get one pulse. is there an easy way to do it with differnt components. the less the better. debounce and square wave is not critical just a brief positive pulse of 5v to reset circuit. Thanks, Steve.. I have a few ne555's to use, I have been having a hard time setting it Up could someone post the values for a 500 ms pulse and a schematic if possible, the only result I am getting is providing a pulse when going from 1 to 0 state. I need 1 pulse when going to 1. any help appreciated!!!!

Also have seen a cd4001 used It looks pretty basic, but, again I am not sure how to figure values? any thoughts on either or?

Checkout the MC14490 chip. It comes with six debouncers.
You can wire two of the debouncers in a way to produce a single
Pulse from the press of a momentary pushbutton. If you use this
chip you won't have to worry about debouncing the pushbutton
either.
I don't know how critical your pulse length Requirement is but
It might work for you...
 
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I have looked at my basics electonics book to come up with a solution that works for me, it is more in the lesser part of the frequency,
. it is not a square wave.... but a pulse with a decay..... ( as far as I can tell it is the components that make other circuits work?) changing R2 gives the values I have stated... I am posting the schematic...... and am looking for input? I thought there would be more response on such a simple thing?
 

eTech

Well-Known Member
I have looked at my basics electonics book to come up with a solution that works for me, it is more in the lesser part of the frequency,
. it is not a square wave.... but a pulse with a decay..... ( as far as I can tell it is the components that make other circuits work?) changing R2 gives the values I have stated... I am posting the schematic...... and am looking for input? I thought there would be more response on such a simple thing?

OK...if you want help, how about showing a complete circuit?
What are you trying to do with this "pulse"?
 
set and reset 2 rs latches through a cd4066. the original circ. is already made, and by going through the 4066, it cannot tell the difference between the manual push of the buttons or the 4066. I have 2 controls tied together, which act as simultainously pushing both buttons together for a brief moment (which controls 2 rs latches together).this seems to work? the pulse is brief at the values posted. changing r2 to a lower ohm value increased (duty cycle) the interesting thing bout the circuit I posted ....... I put it on the O-scope (old pos) when button depressed, appeared to have constant voltage of around .5v? and spike voltage around 4.+ am curious about the actual values of this circ of someone who has better equiptment? my circ is running 5v I needed a pulse because holding the buttons down advances the tool operated which is undesirable. so the pulse starts and stops a circuit, the time the pulse is active is the start duration, then it goes into reset mode

thankyou for your input, I am still interested in other options, but would like the least complex solution, and am also wondering If what I have done looks feasable
 
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