Digital push-button

Konstantinos Guest 2014-06-06 16:21 #3681673

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Dear μController community,

I am a complete beginner in the field so my question might seem a bit 
naive.
In short I need to implement a circuit switch that will change state 
(ON/OFF) every time a short pulse is sent (trigger). In effect it is a 
digital push-button. For instance on a first trigger the circuit open, 
on the 2nd will close..etc..

Do you have any simple solution to this? Is it something easy to 
implement with a μcontroller? I am currently looking for the simplest, 
least time consuming solution so if there is another way other than 
programming ICs please let me know.

Sincerely,
Konstantinos

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MaWin Guest 2014-06-06 16:35 #3681684

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If the circuit does always have power,
than a simple flip flop does

  +-----------+  CD4011
  |       +---)----------------+
  |       +--|>o--10k--+--|>o--+-- on/off
Battery       |        |       1M
  |           |        +--o o--+ 
  +-----------+----------------+


If you loose power, there are specialized
single bit non volatile state saver memory chips like
FM1105B, FM1106, FM1107, FM1110, FM1114 (RamTrom FERAM)

Of course you can program it also into a small micro controller
that has an EEPROM to save state during power loss.
For the Arduino programming environment

char key=0, lastkey=0, savedkey;
const char inputpin = 1;
const char outputpin = 2;
void setup()
    pinMode(inputpin,INPUT); 
void loop()
  while(1)
    key=digitalRead(inputpin);
    if(key==1&&lastkey==0)
      savedkey=EEPROM.read(11);
      savedkey=1savedkey;
      EEPROM.write(11, savedkey);
      digitalWrite(outputpin,savedkey)
    lastkey=key;
    delay(10);

So this is rather simple.

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