third brake light on 4 flat

[dacheedah]

Ok, Trailer wiring question. I found an led stop turn strip. I put two smaller LED's at the top of the trailer as stop turns and hooked the center to running lights and was going to do stop then it dawned on me I was running a four wire system so they are stop turn. I am running a four wire system. Short of running another wire is there a way to grab the stop / turns from both sides, run it through some relays so I can get another center brake on the trailer???

[Flyinfool]

Yes it can be done.

There are a couple of ways to go about it.

 

1. Cheap, quick and dirty. Bring up the left and right turn/stop wires, hook a diode to each one and tie the other end of the diodes together, this then goes to the positive lead of the Third Brake Light (TBL). This will light the TBL whenever either of the stop turn lights are lit. So if you have the brake on the TBL will be lit steady. The down side is that when you have just a turn signal on the TBL will be flashing with the turn signal possibly confusing a driver behind you.

 

2. It can be done with 2 double pole relays (either DPDT or DPST NO) and 2 diodes so that it will work correctly in all conditions. A little more involved to wire up but the TBL will only light when the brake is on as it should be. Schematic attached.

 

3. It can be done with solid state components but would require you to have the ability to make a small simple circuit board, The circuit I laid out would use 2 diodes, 2 NPN transistors, 4 resistors and an SCR on a small heat sink. I have the circuit designed and I have bought the parts, I just have not had time to build it yet to verify that it works as designed.

 

There are some commercially available converters out there, but all of the ones that I found were of option 1, and that will not go on my trailer.

Edited July 19, 2014 by Flyinfool
Schematic link broke

[MiCarl]

I can't think of any way to do it where it wouldn't flash when you had the turn signal on but not the brakes.

 

**EDIT**

 

Jeff sneaked in ahead of me, and I see what he's got in mind. Seems like it'd be easier to just add a 5th wire.........

[Flyinfool]

I can't think of any way to do it where it wouldn't flash when you had the turn signal on but not the brakes.

 

**EDIT**

 

Jeff sneaked in ahead of me, and I see what he's got in mind. Seems like it'd be easier to just add a 5th wire.........

 

Woo Hoo, I almost never beat someone to a post.......

 

While it might be easy to just add the 5th wire you would end up with both the trailer and bike wiring as non standard. Nonstandard is fine as long as you will never pull a trailer for someone else or have someone else pull your trailer or want to pull your trailer behind a car.

You could add the 5th wire as a separate wire with a separate bullet connector, but that is getting to be to Micky Mouse for my taste.

 

My preference if it works is option 3, If I can not get that to work I will do option 2.

[wes0778]

Just a thought but your stop/turn light should have three wires going to it, Left Turn, Right Turn and Ground. If it also has a Run(tail light) function there will be a forth wire. The stop light function comes into play when power is sent to both left turn and right turn wires wires, from your 4 wire tow vehicle. So if you already have a 5-wire to 4-wire converter on the bike you already have your problem solved, I think.....

[dacheedah]

I think I will work on option 2

[Flyinfool]

Just a thought but your stop/turn light should have three wires going to it, Left Turn, Right Turn and Ground. If it also has a Run(tail light) function there will be a forth wire. The stop light function comes into play when power is sent to both left turn and right turn wires wires, from your 4 wire tow vehicle. So if you already have a 5-wire to 4-wire converter on the bike you already have your problem solved, I think.....

 

Ummmmm...

The Stop/turn lights do have 3 wires, but they are ground, Running, and stop/turn. There is no fourth wire. The ones with the fourth wire are simply turn signals that are mounted right next to each other so half of the TBL will still flash with the turn signal even if the brake is on.

[wes0778]

Ummmmm...

The Stop/turn lights do have 3 wires, but they are ground, Running, and stop/turn. There is no fourth wire. The ones with the fourth wire are simply turn signals that are mounted right next to each other so half of the TBL will still flash with the turn signal even if the brake is on.

 

This one has 4 wires (I have this one on my trailer)

http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fspecs%2Ftlb-r11.htm#photos

 

This one just has three, as it does not have the "turn signal" capability

 

http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fspecs%2Fblb-r9.htm#photos

[dacheedah]

The light I have looks like the second one ( 3 wires) ground, I wired running, now looking to do a stop ( third brake light) thing.

[Flyinfool]

Thats exactly what I was referring to, The one that you have on your trailer if you are holding the brake and have a turn signal on, half of the light bar will flash. It will only illuminate solid if the brake is on and the turn signals are off.

 

What the OP and myself are after is a true brake light where you will need some form of electronic mixer as in options 2 or 3 above.

I was planning on getting the same light that you have and using it with my mixer circuit and just tying the green and yellow wires together. This will give me the center and 2 outermost LEDs lit as running lights that are on all of the time and anytime I hit the brake the full bar will light up.

[dacheedah]

Ok wired up and tested, had to switch two wires but this works great. Thanks to flyinfool for his help.

 

 

http://venturerider.org/forum/picture.php?albumid=1039&pictureid=6538

Edited April 8, 2012 by dacheedah

[dacheedah]

Wiring diagram and parts used:

 

http://venturerider.org/forum/picture.php?albumid=1039&pictureid=6538

[playboy]

Nice job that flyinfool is as handy as a pocket on a shirt.

[Flyinfool]

Now come on guys.

Yer gonna make me blush.....

 

Just glad I could help.

[Flyinfool]

OK I have found a source for a TBL controller that is solid state and will make the brake light work correctly.

Square Metal Logic Box, 3 prong.

Just 3 wires to hook up, left turn/brake, right turn/brake and the wire to the brake light.

I have one of these installed on my truck for the center brake light on the topper and it does work as it should.

I do have a call in to the manufacturer to see how many it would take to get a group buy going.

 

At the moment I have a relay version on my trailer, but relays are mechaanical devices and do wear out, contacts fail and are not waterproof. I will be changing this out to the solid state version.