The proposed circuit of a modified car head lamp fader, "breather" circuit generates a slow flashing effect over the head lamps every time the lamps are switched OFF. The "breathing effect" continues for a certain predetermined period after which the process automatically shuts off. The circuit was requested by Mr. Ray.
The Circuit Request
Hey there Swagatam.
I just wanted to say that what you do here in you blog is wonderful. I just came across them in Google looking for a chasing light circuit.
Love it and will be using it. I do have a question about this timer circuit though. Could I have this hooked up to my headlight switch and when I turn off the switch it starts the count?
I would like to add this to a breathing light circuit so when I turn off my lights, the head and tail lights fade in and out for a set amount of time.
Would this be the circuit I need for the timing aspect? Thank you in advance, and there is no rush.
The Circuit Design
The proposed car head lamp fader circuit can be witnessed in the the below given diagram, let's learn about it functioning details:
As long as the main switch stays in switched ON position D2 is held reversed biased, so that T1 is unable to conduct and thus the entire circuit stays switched OFF.
In an event the main head light is switched OFF D2 instantly receives a negative potential via the head lamp filaments which switches ON T1.
T1 now provides the required supply to the IC 4060, which instantly initiates counting process.
C4 makes sure that the IC begins the timing from zero and not randomly when power is switched ON.
C3 makes sure that T1 keeps conducting even while D2 gets reversed biased in response to T3 flashing.
Pin#2 starts counting, while pin#14 begins oscillating at some predetermined rate. The time periods at pin#2 and pin#14 can be optimized by appropriately setting the preset P1.
The oscillating frequency at pin#14 triggers T2 in the corresponding manner which in turn switches T3, and the head lamp, with the required blinking/fading effect.
The slow rise and fall or the "breathing effect" over the lamps is generated together with the help of R6, R7, and C2. The values of these components should be selected and optimized through experimentation for getting an interesting fading effect.
In the meantime as pin#14 generates the pulses, pin#2 counts and as soon as the set time elapses, it becomes high.
The high at pin#2 latches the IC via D1 and also disables T2 from conducting. The situation shuts off the head lamps completely.
The circuit remains locked in this position until the main switch is yet again reset manually to repeat the process.
Parts list for the above car head lamp fader, "breathing effect" generator circuit
R1, R3, R4 = 100K
R2, R9,R5 = 10K
R6, R7 = 470 OHMS
R8 = 50 OHMS, 2 WATT (ARBITRARY)
C1, C4 = 0.1uF
C3 = 100uF/25V
D1, D2 = 1N4148
P1 = 100K PRESET
T4 = BC547T1 = BC557
T2 = 2N2222 OR 8050
T3 = TIP36