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Toggle button using ne555 and digital sig

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Newbie level 2
Dec 27, 2012
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Hi all, I realized a toggle button using ne555, so everything is ok.
Now, I'd like to add the possibility to simulate pressing over digital signal from mcu.
I thought to use a transistor (which should act as a switch) but it does not work, the circuit is closed but not 'clicks' as if it were closed by pressing the button.
The problem is probably due to the logic of charging and discharging of the capacitor, here the two schematic before end after changes. I noticed that every time I press the button, the polarity of the two ends of the button are reversed and so I added a diode to avoid that the current flow over the transistor, this system would be fine only when the polarity of the terminals A and B (indicated in the schematic) were respectively + and -, and not the opposite. I would avoid this solution to use a relay.
I think that it is technically more interesting solve the problem by using a handful of components if possible,
what do you think?

New Happy Year to all.



  • schematic3.jpg
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use proper transistor, because the voltage range would affect in false trigger check for it... otherwise use thyristors(like SCR)...

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you may use try for flip flop that would be easier than 555... where whole thing will be digital...

Hi kanni1303, you suggest an other solution instead of using a ne555 to make a toggle button? unfortunately I do not know others, for this problem no one can give me solution, any suggestion is welcome, thanks.

one thing you have to clear is the voltage across transistor... that would make the undesirable things... because the transistor is designed to be work as switch and can operate in its maximum voltage... you are using 12V that would probably a problm... try with mosfet or some other switching device(most preferred thyristors ) that would operate in the voltage range as that you are getting in that point... first measure the voltage across A and B...

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