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wow that sounded sooo confusing ill just wait for the vendor then lol... thanks for the help wstar....
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To give a better and less cheeky answer:
If you look at the section of the wikipedia entry called Astable Mode , that's describing the kind of circuit you want to build around a 555 timer to get it to flash a small LED, for example. In the diagram there labelled "Standard 555 Astable Circuit", you would put an LED and a resistor of appropriate value (to get the LED's voltage correct) between the line marked OUT and ground, and you've got a flashing LED. Adjusting the values of R1, R2, and C1 in that circuit according to the formulas on that page allows you to change the blinking frequency, and specifically changing R1 and R2 relative to each other allow you to change the duty cycle (like, whether you want the blink to be on for 200ms and off for 800ms, or on for 500 and off for 500, etc). Once you figure out how to blink an LED at the desired frequency and duty cycle with a 555 timer hooked up to a little 5V power supply, the next step is how to integrate this with the F1 rear light ideas. First, to run off of unclean 12V car power, you'd want a voltage regulator to deliver power to your little circuit. A 7805 will provide your circuit with a stable 5V power supply, and can be driven by 7-25V DC on the input side, which is perfect for car input. Then there's the output to consider. The OUT line on that 555 circuit (pin 3 of the 555 timer) can't source enough current to actually drive the rear lamp directly. It would just fry the chip if you tried. So you want to find a small transistor (or really, a small relay might be even better) that the 555 can drive, which in turn delivers the full current 12V to the rear light. The next step is to sort out wiring up the heated seat switch's two on positions and the reverse gear sensor of the car to get the desired effect (normally off in the rear position, normally on when in the forward position, and controlled by the 555 timer output when reverse is engaged in either switch position), which isn't too hard, but I haven't thought it through yet either :) |
Sorry, half asleep. Thanks for the help.
I also did some additional reading on astable mode. As far as I can tell going with a 1K resistor on the R1 side would result in a nice 50/50 on off time. From there I can just choose R2 and C for controlling the actual time back and forth. I don't have any problems with relays so it should be easy to get the output to simply trigger one to illuminate the rear light. I'm slowly learning and may try some simple designs to get familiar with it. Thanks again. |
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Hi everyone, been lurking a couple weeks and as an electrical engineer I impulsively thought I'd throw up a possible solution to the many requests I've seen in this thread. I could build something like what I've shown here pretty easily. Actually, it could all be done with discrete components too, no need for the PIC really. But, the PIC could allow for additional customization such as adjustment of the timing for flashing while in reverse.
This design operates automatically, turning on with fog lights, flashing with reverse and turn signals. No need for extra switches. |
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The reason you don't need an extra switch is because you're in Canada, and you already have a foglamp switch on the switch stalk on your steering wheel. In the US that switch is absent (as is the rear fog lamp itself), although the BCM wiring and the harness all the way to the bumper are present. I think a PIC is overkill for a simple flash, but it would probably be the better option if you want lots of customization, as you said. |
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The design would work without a switch because it can be wired into the existing lights. |
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AFAIK the US model doesn't have any fog lights anywhere to wire to, and no switch to activate them. |
Cherubim, I think there is an opportunity for you to make a little money with this. I know I wouldn't mind paying a little money for a device like this. Flash with reverse and solid on with external switch is all I would need. Let me know if you really consider this.
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^+1 i would pay to get a set up as well
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Lesson learned on the fogs, the design can use a switch as well. Quote:
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Edit: If the intent is to use the rear fog as a rear fog (as well as warn when backing up) then I'd suggest using the bulb that comes in the rear fog assembly. Let me know if you agree as I have the "fog" light bulb type written down at home. |
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