Solid State Brake Light Flasher

Discussion in 'The Projects Forum' started by jj_alukkas, Aug 2, 2009.

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  1. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    Hi,

    I made a brake light flasher for my car using a 555 and a 12v relay to blink two pairs of bulbs alternatively. It works fine but makes a lot of noise each time I step on the brake and it is quite irritating to hear that tic-tic at a traffic signal for a long time. So I designed a solid state circuit of the same. I managed to design the +ve side driver but I have no idea what to do for the -ve side to make it like N/c and N/o of a relay and blink the lights alternatively. Each pair would have a power consumption of 30W(max) I guess.How would I go on for the other side??

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  2. KMoffett

    KMoffett Senior Member

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    If that "tic-tic" irritated you, think how the driver behind you, at that long light, feels about your continuously flashing brake lights in their eyes...especially at night. ....I didn't like it much.

    I did this once, but mine flashed three times when I pressed on the brake, and then stayed on steady.

    Alternating would just require another TIP117 and a 2.7K resistor. Emitter to Brake Line +12, collector to the second bulb, and the resistor from the first TIP117's collector to the second TIP117's base.

    Also, alternating brake lights might cause a lot of confusion for other drivers about your intentions if you are also using your turn signal.

    And in some places this is illegal. ;)

    ken
  3. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    Ya, you are absolutely right, but My car very rarely gets out at night and during the day, you see it only if you look at it. Anyway I plan to remove it cos it may take attention of drivers from far away. I just fitted it today didnt feel muach abt the over-effect at that time. Now I think its not good. Anyway I liked to know how to drive it.

    It might be illegal here too but lots of people do this here and no one cares abt it. But the difference is that those people have small tail lights. So alternating wouldnt cause distraction. But my car has a big tail cluster as its a hatchback with one bulb on the top and other at the bottom which will cause problems. Thanks for pointing it out. Either I'll switch to pulsar ( few blinks and then on) or Ill remove it.
  4. fanie

    fanie Active Member

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    Joseph,

    Personally I don't like 555's, but the idea of the flasher is a good one. Put a diode in line to the 555 and a 100uF cap to isolate it from the 12V.


    You can also design a circuit to flash the brake lights on ie 3 times then stay on using one 4093 gate as slow flip flop to step a 4017. The 4017 is a decade counter. The outputs switches the remaining three 4093 gates in parallel through diodes that drives a FET or relay to switch the brake lights. Bit of logics but you can figure it out. The IRFZ44 is a good choice FET for such an app.
  5. KMoffett

    KMoffett Senior Member

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    This is the one I made several years ago. The PCB was just for layout verification, I actually just point-to-point wired it on perf board. It fit inside the third brake light lense. Three flashes...then steady. :)

    ken

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  6. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    Ya, that chip ,might appear antique but it is almost a universal solution for most circuits. I really started to rely upon them as I have built lots of them in the past and didnt like it in the beginning. But now abt 10 555's serve my daily uses since years. It havent ever failed or malfunctioned so I really like its robust perforance. Thats the 1st reason I use them.

    I have a circuit with a 4093 which does all in one. Ill mostly switch to it.

    And KMoffett, thats almost ditto to the circuit I have. Thanks a lot !!
  7. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    I breadboarded Ken's circuit using CD4093B and it works, but the lamp I tested with was a 12v 3W bulb and it doesnt have much contrast between the On and OFF levels. Is it due to the bulb I am using or will it change when I wire it with the 10W brake bulb. I dont intend to have a full off and On, the current circuit setup is excellent, just I need the light to be a bit more dimmer at the low levels, not completely off either. What to do??

    [​IMG]
  8. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    And by the way Ken, I only recently figured out that the flasher ckt I had saved 2 yrs ago from some website was designed by you. Cheers for you man, keep up the great works.
  9. KMoffett

    KMoffett Senior Member

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    The output should be able to drive the lamp from full off to full (well -2.5 Vsat) on. So, you want the pulses to dim the bulb...or...do you want the bulb normally dim with full-on pulses?

    ken
  10. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    Sorry, it was a wiring mistake.. In the replacement of the driving transistors, I accidently swaped the E & C of BC547. Now what I only need is how to alternate 2 sets of bulbs. The current setup works fine with a 15W 12V bulb. I am using TIP127, which being a 65W darlington pair, will it be able to drive, say 30-40 W easily. It will need a heatsink, but will it be in stress? Also I like to alternate the upper and lower lights during the flash, so I plan to connect another TIP127 to this one with the 2nd ones Emitter to +12, collector to second bulb and base to 1st Tip's collector through a 2K7.. will it fine?? Also is there a slight modification possibilty to make the 2 TIP's stay on after the pulsing period instead of only the first one alone??
    Last edited: Aug 19, 2009
  11. KMoffett

    KMoffett Senior Member

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    For full-on/full-off of higher wattage lamps you might want to drop R9 and replace Q2 with a low Ron, p-channel, power MOSFET. Much lower power dissipation in the MOSFET than the darlingtons. The thermal time lag in the bigger lamps may do you dimming.

    As for alternating lamps, ending with both on...maybe an gated oscillator (4093) driving a 4017 counter. Diode OR-ing the counter outputs so outputs 0/2/4/6/8 drive lamp1, outputs 1/3/5/7 drive lamp2, output 9 drives both lamps1, lamp2, and kills the oscillator. No schematic...just an idea.

    If you absolutely need dimming, I would go with a small microprocessor driving MOSFETs with PWM. Then you can do any sequencing and dimming you can imagine. ;)

    Ken
  12. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    The lighting setup is completely fine as well as its timing, I just want another set to alternate. Its ok if it wont remain lit after the blink, but is the connection for the second TIP I stated correct?? MOSFETS's would have been more efficient, but this thing lights only for a few seconds, so its ok I think.
  13. KMoffett

    KMoffett Senior Member

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    Yes. It should work.

    ken
  14. SIcam

    SIcam Active Member

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    There is a Federal Requirement for the flash rate and duty cycle of a turn signal.

    FMVSS 108 details the requirements.

    If you alter the Federal requirements on a vehicle and are in an accident the changes that do not meet the requirements could be used against you.

    Solid State blinker flashers are needed over thermal flashers due to the low current draw on some LED lighting.
  15. KMoffett

    KMoffett Senior Member

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    SIcam,

    Did you check JJ's location? I don't think he'll be concerned about our Federal requirements. No clue as to what the Indian government mandates are. From our discussion I think JJ is using conventional incandescent lamps, not LEDs.

    Ken
  16. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    Yes Ken, you are right, we have no problems here with such lights.

    And Yes, im using incandescent lamps, just an extra ckt to the current tail cluster. I'd love to make an LED one, but since the tail set integrates the normal types, I left the plan as I would have to crack open the clear lens. Anyway thanks Ken, Love your design.
  17. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    Actually I use them despite the heat loss since it irritates me with its sound, otherwise I would only prefer relays.
  18. SIcam

    SIcam Active Member

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    Sorry, didnt realize you were in another country.

    What does (+5.5) at the end mean?
  19. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    5 hrs 30 mins more than Greenwhich mean time(GMT) . I guess US is abt -6 hrs. So a total of 5.30 + 6 = 11.3 hrs difference b/n indian and US time.
  20. jj_alukkas

    jj_alukkas Thread Starter Well-Known Member

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    If I invert Pins 3 and 11 using transistors and OR them using diodes, will I have 2 lights alternating during the flash and both lit up after the flash period? I found this to use fewer and simpler components than to invert Pin 12 and NAND it with pin 3. Also, how do I create a NOT using a single NPN transistor? I know the connections, but biasing resistor values seems to be wrong according to my ideas.
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