In this tutorial, we are going to learn about Double Blinker Circuit.
Double Blinker – Up to now always some kind of external action was necessary to switch a circuit from one state into another. In contrast to this behavior the warning light in this chapter will operate completely automatically. The circuit switches all by itself from one state to the other. Such blinking lights are always used if a special attention is required. For example, a continuously on LED may indicate the normal operation of a refrigerator. But if the cooling aggregate fails, the LED is switched into blink mode. Now even a brief look reveals that come actions is required. Specifically in traffic blinking lights are used frequently. The classical examples are the turns signals. But also at railroad crossing, bcted linking lights are used to raise maximum attention if a train approaches .Finally the vehicles of police and fire brigade are using flashing lights to indicate their priority in heavy traffic.
How does the circuit work?
Only a small variation is required, to change the pedestrian traffic light into the double blinker. Only one 100K ohm resistor must be placed differently and a 100 muF capacitor has to be added. Furthermore, the push button is not required any more of course. The circuit is now completely symmetric and only small tolerance in the components determines, Which LED comes up first when the set-up is connected to the battery.If the red led comes up first, then the green one must remain dark, since only one transistor can be conductive at a given time. This is due to the cross connection of the transistor bases to the collectors.While the red LED is on, the right capacitor is charging up, while the left one remains uncharged. Only if the capacitor reached a certain voltage level, Q1 starts to conduct and Q2 becomes nonconductive. Now the right capacitor charges up until the circuit flips over again and the game starts a new.
If the 100K Ohm resistors are used , the LED are blinking relatively slow. Using 10 Kohm resistors instead increases the rhythm significantly.