Blinking third break light

Is that legal? BTW yesterday driving behind car with driver side rear brake light out of action realized that's another advantage of the third brake light set up! With only two lights you may not know, when one is out of action whether the driver is trying to signal a turn or is tapping his brakes. The third and upper light tells you 'Yes it's the brakes'. (That assumes that only one regularly located brake bulb is out of action and the third (and usually upper brake light) is OK.

Wha? On my American-made truck the turn signal is orange and the brake light red.

Mistaking a brake light for a turn signal has not been a problem in the advanced world since 1960. Only the flat earth society (USA) has persisted with this cheapskate method for so long.

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John G

Wot\'s Your Real Problem?

Bryan, there have been a few posts in reply to your question but other than to raise the quasi relevant question of legality (I've seen them flash on motorcycles) they're not really addressing your question.

The good news is 1) I know how to do it, 2) I've seen and have a schematic for something really similar. The bad news is that I'm not expert so my experiences and knowledge are limited (kinda the deaf, dumb, and blind leading the blind. :)

That said, I read this schematic about 5 years ago and it was for flashing the brake light on a motorcycle. There are two ways you can decide to have that light flash; continuously while the brake light circuit is energized or to have it flash some number of times and then latch on (blink - blink - blink - stay on....). Either of them will be simple to implement.

Let's put into words that which is easier said than done; locate the wire that runs to the Elizabeth Dole light (third brake light), preferably somewhere inside the car instead of inside the housing (for space, appearance, and accessibility considerations). Bascially, just cut the positive wire that goes to that brake light. The raw end of the wire from the chassis is now your source voltage; it should have voltage only when the brake light circuit is energized. The other raw end, that goes to the Elizabeth Dole light is the output that you'll hook up to your circuit you're going to build.

The circuit I use consists of basically 8 parts: one potentiometer (100k), one capacitor (10 micro F), one 4049 hex buffer, one 4017 decade counter, one 680 Ohm resistors ,x number of 4148 diodes (the number of outputs from the 4017 you intend to use), 1 2N4401 transistor, one more 4148 diode, and finally one relay.

It's a really simple thing once you've played with it and seen it (believe me, electronics isn't my area of expertise and yet I think it's pretty simple). The 4017 decade counter does just what it seems like it would do; it counts input pulses. It sends one of 10 outputs high (on) depending on the number of input pulses it gets. I use the

4049 hex buffer to generate the pulses (I have no idea how it does it, I just read it in the original schematic I read). I tried to use a 555 timer to produce the pulses but could never get it to work right. Anyway, the capacitor is used with the 4049 hex buffer I presume as a filter, and the pot is used to adjust the output pulse frequency. The 4017 receives the pulses as input and sends each of its outputs high in turn. You tie the output through a diode to the resistor. Then, finally, you tie in the transistor, final diode, and relay. I don't know why they used the transistor, but I suspect it's because the 4017 might not be able to sustain the load of the relay on it's outputs. Here's where it gets fun.

If you want it to blink on and off three times and then stay on you simply tie outputs 1, 3, 5, through diodes, to the resistor which is tied to the transistor. Then you tie output 7 to the resistor AND to the Clock Enable pin on the 4017 (tying its own output #7 to the Clock Enable) which "freezes" the whole thing. It'll stay locked on like that until the whole circuit gets reset (when the circuit loses power when the brake circuit de-energizes as the pedal is released). The output trips on the transistor which applies power (from the up-stream brake circuit) to the relay (any NO automotive relay that can handle the load (check out a horn relay for a 1998 Dodge Ram 1500 at an autoparts store for around 8 bucks and which has nice-sized legs for female blade connectors)). You use the second 4148 to kill any spike voltage from the coil in the relay.

Now, I've never tried to see if one will reset when you cut power to it, but the original schematic that I saw worked that way, I *think*.

Unfortunately, it's near impossible to try to describe to you what the connections/schematic looks like in type. This link is now dead, but if you could find some web archive site they might have it (I never looked at this site/page before so I don't know if it would do what you need or not):

Here's a link to a, I think, much more complicated setup, but the schematic is nice and clean:

Unfortunately I don't have a site that would be available long enough or reliably enough to post it in this reply. I can draw something up and e-mail it to you, if you'd like, just let me know and post your address and I'll see what I can do.

In the meantime, here's a simple idea...if you don't mind it flashing constantly:

Super simple, it looks.

Anyway, hope that helps.

Take care.

--HC

Once again you are full of misinformation about the US. Tail lights on vehicles abandonded this method a long time ago.

Idoits spouting garbage comes to mind.

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Michael A. Terrell
Central Florida

Thanks for the information. I should have been more clear on the blinking area. I did wants it for a duration they steady on. I have seen some vehicles with this in Arizona as far as the legality aspect, I have not heard of any. I do have a motorcycle as well and was looking to adapt the circuit to it as well as using LEDs. Thanks again for your help. I will look into those sites. If you have any other ideas as well, please feel free to let me know.

BA Sr.

I have a drawing of the circuit, as an Adobe Acrobat document, and I could prbably hack one out in Paint (I originally used Corel Draw! to make the schematic, converted it to PDF and God only knows where that Corel Draw! file went. :-/ I hate to be an ignorant wretch, but I don' t know how to post a file to the 'groups. I'd be willing to send you my schematic as a PDF, but I'd really like to do it here in the 'groups so others could benefit from it. Any suggestions of how I can "post" a PDF in a 'group posting?

I can always send it to your e-mail address if you want to give that to me, but like I say, I'd really like to send it to the group to help you AND others.

--HC

Actually, I'm pretty sure I saw a recent model Ford that had the brake/turn signal use the same lighting element. Flat earth, huh? OK GG

It would be interesting because Ford claims to build "International Designs". My neighbor bought a new full size Ford truck last year so I'll check when I catch her at home. I don't recall seeing any new vehicles without the separate light systems and it makes hauling a conventional trailer even more interesting with all the variations in wiring. On top of that, a lot of vehicles are imported from other countries that use separate lamps for turn and brake lights.

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?

Michael A. Terrell
Central Florida

Hey, I dunno if I did this right but I'll try it anyway. This is a stripped down copy of the file I had for another project. It's a UUE encoded ZIP file of a PDF. :) Basically you'll see that this circuit pulses a relay the a number of times and then sets it on. Using the brakelight wire from the vehicle that currently runs to the light as the power source should be the optimal source of all 12v+ power shown in the diagram. You might have to run pin 15 (I think it is, shown with a switch that goes from positive voltage to ground) directly to ground to get it to always be ready to run. I haven't built the circuit exactly as it's shown in this diagram but I have built it with multiple relays so I know the basic circuit shown will work.

I hope this file will post properly, if not I'll do some more testing and see what I can do. Any suggestions would be appreciated.

Thanks.

--HC

_=_ _=_ Part 001 of 001 of file Blinker.zip _=_

begin 666 Blinker.zip M4$L#!!0``@`(`!!Y>#(#:A>6?:

Well, that's not perfect but I guess it'll work; it's all text, it should propagate beyond Google (I hope) and anybody with a copy of Winzip can copy and paste it into a straight text file (Notepad), save it as blinker.uue and then open it with Winzip.

--HC