In fact, it’s possible to design an LED chaser with several LEDs by using shift registers. In this sequencer, seven LEDs are interfaced with Arduino to demonstrate 13 different lighting patterns. Arduino is currently the most popular single-board microcontroller. In a chaser or sequencer circuit, a controller commands the sequence and timing of the flashing LEDs to illuminate different kinds of lighting patterns. It’s used in running-light rope displays to flash different lighting patterns. This same flasher can easily be built with a microcontroller like arduino.An LED chaser or sequencer is a popular LED driving circuit. To see a project of an LED flasher being built with an arduino board, seeĪrduino LED Flasher Circuit. The schematic diagram of the 2 flashing alternative LEDs is shown below:Īgain, this will create a circuit where 2 LEDs now flash, alternative, like police sirens rotating between a blue siren and aĪnd this is how LED flasher circuits can be built with 555 timers. We need all the parts listed for the first circuit, now with the addition of 1 more 1KΩ resistor and 1 red LED. This happens pretty quickly but it still can be seen with the human eye. As one flashes on, the other flashes off. We can slightly modify the circuit above so that it flashes 2 LEDs. These values for resistors R1 and R2 and capacitor C1 allows us to see the flashing of the LED. With R1= 1KΩ and R2=10KΩ and C1= 10♟, our calculations will be: With a 50% duty cycle, the LEDs are on for about the same time that they are off. With these values, each cycle would last just a few millionths of a second.įor the values we must in our circuit, our duty cycle is just about 50%. Therefore, we must choose a precise range of It will be as if the LED is constantly on. If we choose 1KΩ resistors and a 0.1♟ capacitor, the time cycle and the on-off cycle would be too short. If we do, the human eye won't be able to detect that it has even turned on. However, on the other extreme, we do not want to choose values which are too small as well. In order to see a flashing or flickering effect. We must choose much lower resistor and capacitor values The LED would be on for 140s and off for 70s. This would produce a total time period of 210 seconds for the cycle. For example, let's say we make R1 and R2 resistors both 1MΩ resistors and C1 100♟. If we use very large values such as 100KΩ or 100♟, It's also why you must double R2 but not R1 for the total time (T) calculation.Īccording to the above formulas, the larger value we use for the resistors and the capacitor, the longer the cycle will be. That's why we must add the 2 resistor values for the T high calculation, but only use R2 for the The formulas to calculate these values in our circuit is:Ĭ1 charges through both R1 and R2 but discharges only through R2. Will be on for 80% of the cycle and off for 20% of the cycle.

If we choose a duty cycle of 80%, the LED Again, as an example, if we set our duty cycle to be 20%, this means the LED will flash on for 20% of the cycle and be off for 80% of the cycle. The duty cycle we choose determines how long the LED will stay on for compared to how long it is The duty cycle is very important for an application like this LED flasher circuit. So, for example, if the total time of a square wave is 1 secondĪnd it's high for 0.2s, it has a duty cycle of 20%, because it's on for only 20% of the cycle. The amount of time that the square wave is high is its duty cycle.

There is the total length of the square wave (the time it is onĪnd off or high and low), there is the length of time it is high (T high), and the length of time it is low (T low). There are 3 important time measurements for a square wave. The rate that the LED flashes is determined by the resistors R1 and R2 and the electrolytic capacitor C1.Īgain, the output of a 555 timer are square waves. This circuit will flash the LED on and off, on and off. The schematic diagram of the LED flasher circuit we will build is shown below: To simply the breadboarding of this circuit, jumper wires help to space out the circuit so that everything isn't jumbled To create an LED flasher circuit, the parts which we need to do so are:įor this circuit, you can use a 9-volt battery as the power source or if you have a DC power supply, you can just adjust so thatįor this circuit, you will need several jumper wires because to connect all the resistors and capacitors to the 555 timer chipĭoes become complicated. This is why this mode is also called oscillator mode, because it uses the 555 timer an oscillator, which creates square wave signals. Astable mode simply means that the 555 timer has no stable state.

To make the 555 timer chip create pulses, it must be placed in astable mode.

Arduino as timer for strobe light