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ericmar
Joined: 14 Apr 2004
Posts: 279
Location: Singapore
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 23 Feb 2005 13:47 How can I hold the signal cause by pushing momentary button? |
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Is there anyway that I can design a simple circuit which hold the signal cause by pushing momentary button?
For example, I have a momentary button and I want my circuit to hold the signal when I press the button so that I can move a thing from one place to another place. After the thing reaches the destination, the signal will then be released and stop the moving operation.
I'm not using any microcontroller becoz I want to design a logic circuit.
Thx for help in advance!
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dkace
Joined: 13 Jun 2002
Posts: 356
Helped: 24
Location: Greece
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| 23 Feb 2005 15:09 Re: How can I hold the signal cause by pushing momentary but |
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Try a Schmidt trigger. Check applications. I think it is the best latch for this kind of applications,
D.
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M!k
Joined: 22 Apr 2002
Posts: 815
Helped: 69
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| 23 Feb 2005 17:02 Re: How can I hold the signal cause by pushing momentary but |
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sorry dkace, Schmidt trigger is the wrong keyword. A Schmidt trigger is only a kind of input circuit, often used for chattering contacts. But it doesn't store a signal.
Storing a short trigger pulse can be done by using a Flipflop. Search on google for RS- or better JK-Flipflop. Generally these devices have a set and a reset input. So you'd connect your pushbutton to the set input and a second switch at the destination position to the reset input.
Mik
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dkace
Joined: 13 Jun 2002
Posts: 356
Helped: 24
Location: Greece
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| 23 Feb 2005 17:38 Re: How can I hold the signal cause by pushing momentary but |
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Right M!k, I am sorry. A flipflop can be used for this application, not a ST. I was working with one by that time and I was too focused I guess.
But that's why the forum is...
D.
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artem
Joined: 22 May 2003
Posts: 1641
Helped: 90
Location: Turan
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| 23 Feb 2005 17:55 How can I hold the signal cause by pushing momentary button? |
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If your signal is chnaging in time and you would like to have it unchanged after your magic button will be released , you should implement something like ring buffer in programming . There should be one input and one outoput from this ring buffer . signal sample is written into ring buffer input and output is connected to buton controlled circuit as when you press button no signal output will work , but signal will still be recorded through input .
it does not matter whether you have analog or digital - same principle applied to both . You should take rign buffer (memory) length into concideration as it defines how long you can hold your button .
P.S.Do you need this or it is IQ test question 
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kennyg
Joined: 10 Jan 2005
Posts: 49
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| 24 Feb 2005 16:20 Re: How can I hold the signal cause by pushing momentary but |
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Hello,maybe a sample-and-hold circuit fit your need.
if FET cutoff-->
vout=voltage between capacitor
=v-HOLD
if
FET conducting--->
vout=vin=v-SAMPLE by feedback.
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yeechyan
Joined: 14 Jun 2004
Posts: 111
Helped: 1
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| 27 Feb 2005 5:06 How can I hold the signal cause by pushing momentary button? |
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| You can use a MOSFET or a thyristor to store the momentary signal.
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e_eja
Joined: 15 Nov 2003
Posts: 145
Helped: 4
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| 27 Feb 2005 15:56 Re: How can I hold the signal cause by pushing momentary but |
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| use analog switch, the control allowed use digital signal meanwhile could allowed analog signal tobe controlled
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dkace
Joined: 13 Jun 2002
Posts: 356
Helped: 24
Location: Greece
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| 27 Feb 2005 21:23 Re: How can I hold the signal cause by pushing momentary but |
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Hi again,
in Sedra /Smith I found in multivibrators section this very interesting circuit for your application. The output is control by the trigger input and is a pulse whos width is control by C1R3. Check it out, it might serve your purpose better.
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