Saturday, March 28, 2015

Timer 555 first project

A first project with no Arduino or Raspberry PI. Two Timer 555, capacitors, resistors and one light sensor. The device is powered by a mini USB, to be  plugged into any computer USB plug or USB adapter.

When pressing the button, the LED will blink for about 45 seconds and the Piezzo speaker will make a tick for each blink. The light sensor control the speed of the blinking. The more light the faster, the less light the slower.

See video.

Timer 555, 2 LEDs Blinking Schematic:

1. Pin1 to ground
2. Pin2(trigger) to pin6(Threshold)
3. Pin8(Vcc) to pin4(Reset)
4. Pin7(Discharge) to pin8(Vcc) using 4.7k Ohm resistor
5. Connect 47uF Capacitor negative pin to ground
6. Connect 47uF Capacitor positive pin to pin6 (threshold)
7. Connect 47uF Capacitor positive pin to pin7(Discharge) 
  using 10k + 4.7k resistor
  or using LightSensor + 4.7k resistor
8. Connectpin3(Output) to Empty Row
 8.1 2 red   led: Empty row -> 1k Ohm Resistor -> -RED-LED1+ -> -RED-LED2+ -> Vcc
 8.2 1 green led: Empty row -> 100 Ohm Resistor -> +GREEN-LED2 -> GREEN-LED2-> Ground
9. Connect Pin8(Vcc) to Power

Timer 555, Monostable Mode, one time timer
var C = 470uF
var Ra = 22k => 5.17 seconds

1. Connect power and ground to pins 8 and 1 of the 555 timer (red and black wires).  
2. Connect a 0.01uF capacitor between pins 5 and 1.  
3. Connect a 470uF capacitor between pins 1 and 6, make sure that the negative lead of the capacitor is connected to pin 1.  
4. Connect pins 6 and 7 with a jumper wire (green).  
5. Connect a 47K resistor between pins 7 and 8.  
  47K + 470uF = 25s of animation
6. Connect pins 4 and to Vcc
7. Connect LED+ to pin 3 and LED- to goun
8. Connect an LED and current limiting resistor in series from the output of the 555 to ground.  
9. Connect Wire the momentary push button switch in series with a 10K resistor between Vcc and ground.    
   Connect a wire (yellow) from the junction between the switch and resistor to the trigger pin 2

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