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help with simple circuit

E

Eric

Jan 1, 1970
0
I'm very new to electronics so this is probably a pretty basic circuit
that I need to build. Here's what I'm trying to do. I currently have
a manual switch that is control by a moving object. When the object
hits the switch, the switch is turn on and the circuit is completed.
The problem is that sometimes the object hits the switch multiple
times in a single pass. I'm looking for a way to basically add a
timer or delay so that after the switch is completed once it will take
x time until it can be completed again. From my basic knowledge I was
thinking that a capacitor with a variable pot could do what I want. I
would like to here some thoughs on this simple problem.

Thanks,

Eric
 
T

Tim Wescott

Jan 1, 1970
0
Eric said:
I'm very new to electronics so this is probably a pretty basic circuit
that I need to build. Here's what I'm trying to do. I currently have
a manual switch that is control by a moving object. When the object
hits the switch, the switch is turn on and the circuit is completed.
The problem is that sometimes the object hits the switch multiple
times in a single pass. I'm looking for a way to basically add a
timer or delay so that after the switch is completed once it will take
x time until it can be completed again. From my basic knowledge I was
thinking that a capacitor with a variable pot could do what I want. I
would like to here some thoughs on this simple problem.

Thanks,

Eric

Find a datasheet for a 555 timer that has a debounce circuit.
 
C

CFoley1064

Jan 1, 1970
0
Subject: help with simple circuit
From: [email protected] (Eric)
Date: 7/14/2004 2:39 PM Central Daylight Time
Message-id: <[email protected]>

I'm very new to electronics so this is probably a pretty basic circuit
that I need to build. Here's what I'm trying to do. I currently have
a manual switch that is control by a moving object. When the object
hits the switch, the switch is turn on and the circuit is completed.
The problem is that sometimes the object hits the switch multiple
times in a single pass. I'm looking for a way to basically add a
timer or delay so that after the switch is completed once it will take
x time until it can be completed again. From my basic knowledge I was
thinking that a capacitor with a variable pot could do what I want. I
would like to here some thoughs on this simple problem.

Thanks,

Eric

Hi, Eric. First, you might want to try looking at your switch. Microswitches
are made with built-in mechanical hysteresis to prevent what you're talking
about. They are made to snap on with a certain amount of detent on the switch,
and then the switch arm will have to move back significantly before the switch
snaps off. A microswitch is the right switch for this job.

Having said that, you still have to look at the issue of contact bounce, which
occurs even in microswitches. Contact bounce usually occurs too quickly too
have multiple turn-on/turn-off cycles on a relay or other physical load
(although some slower switches can cause multiple hits on fast reed relays).
Contact bounce usually occurs over several milliseconds, which can be a problem
when interfacing a switch with control logic operating in the ns/us range.

Another post suggested a 555 debounce circuit, which might work well for slow
make/slow break switches as well as contact bounce. There are other solutions,
too. How about giving some information on your circuit, like what kind of
switch you have, what power source is being switched, what's the switch load,
and the other details. If you've got a circuit where 120VAC is being switched
to drive a relay or lamp load, a 555 might not be the appropriate solution.

You might get a more enthusiastic response to a basic newbie question on
sci.electronics.basics

Good luck
Chris
 
P

petrus bitbyter

Jan 1, 1970
0
Eric said:
I'm very new to electronics so this is probably a pretty basic circuit
that I need to build. Here's what I'm trying to do. I currently have
a manual switch that is control by a moving object. When the object
hits the switch, the switch is turn on and the circuit is completed.
The problem is that sometimes the object hits the switch multiple
times in a single pass. I'm looking for a way to basically add a
timer or delay so that after the switch is completed once it will take
x time until it can be completed again. From my basic knowledge I was
thinking that a capacitor with a variable pot could do what I want. I
would like to here some thoughs on this simple problem.

Thanks,

Eric

Eric,

You did not provide enough information to obtain a reasonable answer.

What does the switch look like? Current, voltage i.e. what does it have to
switch? On or off? What kind of power is available? How long will it take to
be sure the next hit is a wanted one? Or reverse, what is the maximum time
in which a false hit can be expected?

That's not to say there is no answer. It sounds: Take a 555. Use it as a
non-retriggerable monostable. Trigger it with you switch and make it drive a
relay that drives the load. But if you understand this, you would not have
put your question.

BTW. That's why this question should have been placed in
sci.electronics.basic.

petrus bitbyter
 
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