# Simple Delay/Presicion Question about a switch(pic included)

Discussion in 'The Projects Forum' started by Selportion, Apr 5, 2011.

1. ### Selportion Thread Starter New Member

Mar 21, 2011
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0
The circuit is as below:
http://img98.imageshack.us/i/circuitc.jpg
(Using ~6VDc, simple wiring, 2 proper NAND gates and big resistors)

• I want (D) to become (0) if the switch between (A)-(B) closes by itself (C is 0, its negative 1, B becomes 1, so D turns 0)
• I want (D) to become (1) if the switch closed while touching (C) also. (C becomes 1, its negative 0, B becomes also 1, so D remaings 1)
The problem is that on the 2nd occasion there are some microseconds that the switch is closed before (C) is fully triggered or (C) gets untriggered before the switch fully opens, so for some fragments of time (D) becomes (0), unwanted, and triggers 555s and other circuits after that.

I cannot fix that mechanically/physically. Do you think there is any simple electronic solution like with capacitors and resistors or something? I want to avoid more 555s.

Any help is welcome and appreciated!

2. ### HallMark Member

Apr 3, 2011
89
5
I am not able to see Image you have posted please choose another Image hosting or use the attachment facility of AAC.

Mar 21, 2011
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4. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
Didnt understood make it a bit clear,like as per your circuit you have two input "B" and "C" and one output "D" now just write a truth table for that (its easy) after that we may help you with your circuit.

Good luck

5. ### Selportion Thread Starter New Member

Mar 21, 2011
8
0
Ok here's more clear. B,C inputs / D output. I want:
B C D
0 0 1 <<natural state>>
0 1 1
1 0 0 <<Switch A-B closed>>
1 1 1 <<Switch A-B closed with C touching>>

But on the occasion of (B=1/C=1) for some milliseconds it turns D=0 because
-> C delays becoming 1 on touch or
-> C becomes 0 too fast before B becomes 0 on release.
so it jumps for an instance to the 3rd state.

Last edited: Apr 5, 2011
6. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
What is the application of this circuit because what you are asking for its not much problem in general circuits but in some case it is so, it will helpfull for us if you provide some info about the system where you are using this stuff.

7. ### Selportion Thread Starter New Member

Mar 21, 2011
8
0
It's a game in which a button sometimes hits targets or sometimes environment stuff. But i cannot intervene with the touching mechanism, i need something to delay B turning 1 and delay C going back to 0... Is there any way with capacitors, resistances or something?

Jul 1, 2008
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