one time pulse with a 555 timer
one time pulse with a 555 timer
(OP)
Hello
I am trying to keep it as simple as possible. I have scoured loads of sites etc, an have even found the circuit I want, or should I say it is described as the one I want.
I have found a simple circuit which I replaced R with a potentiometer to make the output variable, but the aim is to make this a one time circuit. I want to push a current through the circuit it fire for a variable amount of time (via the potentiometer), then stop even though the trigger has not.
I have been told that this is done with the use of and extra capacitor, resistor, LED and Transistor (used as a not gate) to get this to work. So far all of the layouts I have been given have not worked.
I seen the post at thread240-151528 (sorry could not find how to add it as a link). Seemed to be asking a similar question and woundered if that was the way to go? Any ideas would be great.
Thanks
Scott
I am trying to keep it as simple as possible. I have scoured loads of sites etc, an have even found the circuit I want, or should I say it is described as the one I want.
I have found a simple circuit which I replaced R with a potentiometer to make the output variable, but the aim is to make this a one time circuit. I want to push a current through the circuit it fire for a variable amount of time (via the potentiometer), then stop even though the trigger has not.
I have been told that this is done with the use of and extra capacitor, resistor, LED and Transistor (used as a not gate) to get this to work. So far all of the layouts I have been given have not worked.
I seen the post at thread240-151528 (sorry could not find how to add it as a link). Seemed to be asking a similar question and woundered if that was the way to go? Any ideas would be great.
Thanks
Scott





RE: one time pulse with a 555 timer
You will find a lot of circuits to do what you want.
Here's the second one on the list:
h
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: one time pulse with a 555 timer
Sorry if I am sounding dumb here.
RE: one time pulse with a 555 timer
respectfully
RE: one time pulse with a 555 timer
http:
RE: one time pulse with a 555 timer
You want a __--__ pulse at the beginning of the trigger
pulses? How long ?
Plesae read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: one time pulse with a 555 timer
Sounds like a 'Power On Reset' circuit. Apply power to the circuit, and get a nice clean reset pulse. There are a million solutions including application-specific 3-terminal devices. Most POR emit a low-going reset pulse (ground seeking) - but inverters are easy.
RE: one time pulse with a 555 timer
TTFN
RE: one time pulse with a 555 timer
I have read through all of the material given and it seems similar to what I have tried. Most of them continued to pulse the motor as the input was still high.
RE: one time pulse with a 555 timer
Let be R1=1 Mohm, R2=1kohm, C1=.1 microF. Sw1 = Normally open switch. (each line is one node, each part has
two pins, 1. and 2. )
V+ --- R1.1
R1.2---C1.1---Sw1.1
C1.2---GND
Sw1.2 ---R2.1--- 555.trigger
R2.2---GND
When the SW is open the C1 charges up to V+ through
R1 in about .1 sec. When Sw is closed, C1 discharges
through R2, generating a single positive pulse of about
.0001 sec. Use this to trigger the 555
Plesae read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: one time pulse with a 555 timer
TTFN
RE: one time pulse with a 555 timer
Even if he uses 121, the trigger must be debounced or otherwise it may trigger on both edges.
Plesae read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: one time pulse with a 555 timer
Plesae read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: one time pulse with a 555 timer
TTFN
RE: one time pulse with a 555 timer
The leading edge is ok, but the trailing edge may bounce, too.
By the way, the 555 has higher current and can either sink or source.
Plesae read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>