Unique wiring challenge on travel trailer

Thread Starter

Farmaller48

Joined Jun 30, 2016
25
Well, it does sound like something may be wrong with the meter.
If the LED didn't light then you had no continuity through the meter.
Perhaps it's fused and the fuse blew.
Update to the process: I ran a voltage test on the feed from the PWM with the truck brakes applied at varying levels. Max voltage to the trailer brakes was 4.2v. Even with a capacitor in the circuit leading to the relay, would that be near enough root voltage to activate the relay?

Also, it has occurred to me that this travel trailer has an onboard 12v battery (as most do), so a source of constant and steady 12v power for the new 3rd LED brake light is right there onboard.
 

tcmtech

Joined Nov 4, 2013
2,867
Actually, tcmtech, the LED light is not dimming but intensifying slightly (spiking) when the right or left side stock tail light is in blinker mode. I assume this is the result of voltage bleeding over from that side into the LED light. Is there something that can be put in the lines leading from each side to the LED light in my diagram that would suppress the voltage bleed over?
Knowing the actual at the light voltage levels when things are happening would be a great help.
 

crutschow

Joined Mar 14, 2008
25,669
Update to the process: I ran a voltage test on the feed from the PWM with the truck brakes applied at varying levels. Max voltage to the trailer brakes was 4.2v. Even with a capacitor in the circuit leading to the relay, would that be near enough root voltage to activate the relay?
..............................
You need to add a diode in series with the capacitor as I showed in my diagram, to capture the peak voltage. Why did you think the diode was not needed?
You are measuring the average voltage of the PWM signal, which indeed will not be 12V.
 

Thread Starter

Farmaller48

Joined Jun 30, 2016
25
You need to add a diode in series with the capacitor as I showed in my diagram, to capture the peak voltage. Why did you think the diode was not needed?
You are measuring the average voltage of the PWM signal, which indeed will not be 12V.
No sir, I wasn't working under the impression that I could skip the relay. I believe you're totally correct on that. I was just asking if you felt like the voltage measured on the pwm output (4.2) would be sufficient to sufficiently charged the capacitor and subsequently trigger the relay.
 

crutschow

Joined Mar 14, 2008
25,669
No sir, I wasn't working under the impression that I could skip the relay. I believe you're totally correct on that. I was just asking if you felt like the voltage measured on the pwm output (4.2) would be sufficient to sufficiently charged the capacitor and subsequently trigger the relay.
Did I mention the relay? :confused:
I'm taking about the diode.
You need to measure the voltage with the diode in series with the capacitor to ground as shown in my diagram.
Is that not clear?
Perhaps if you read about a PWM signal you will better understand.
The signal should be pulsing to a peak voltage of about 12V and that is the voltage we need to capture, not the average.
No, the average voltage you measured will not pull in the relay but that voltage is irrelevant to the discussion.
 

Thread Starter

Farmaller48

Joined Jun 30, 2016
25
Did I mention the relay? :confused:
I'm taking about the diode.
You need to measure the voltage with the diode in series with the capacitor to ground as shown in my diagram.
Is that not clear?
Perhaps if you read about a PWM signal you will better understand.
The signal should be pulsing to a peak voltage of about 12V and that is the voltage we need to capture, not the average.
No, the average voltage you measured will not pull in the relay but that voltage is irrelevant to the discussion.
No sir, you didn't mention the relay. That was simply a mistake in my reply. It was supposed to say diode where I said relay. I will certainly take your advice to research and learn PWM signal. I genuinely appreciate the help you have tried to provide through the course of our conversation, but I can tell by the quickly changing tone in your replies that I have worn out my welcome. My apologies for the frustration I have apparently caused you. Thanks again.

BTW... may I offer you a suggestion as well? In the future, when a self-admitted novice comes to your forum seeking help from those of you who are supposedly participating with a willingness to help someone who knows less than you do, if you find yourself frustrated with the course of conversation with that less-knowledgeable person, instead of taking a tone with them that is geared toward making them feel like an idiot, perhaps you could consider it just simply not engaging in the conversation with them any further. I feel like I did my very best to show you respect and appreciation throughout the course of our conversation. "Do unto others..."
 

tcmtech

Joined Nov 4, 2013
2,867
I genuinely appreciate the help you have tried to provide through the course of our conversation, but I can tell by the quickly changing tone in your replies that I have worn out my welcome. My apologies for the frustration I have apparently caused you. Thanks again.

BTW... may I offer you a suggestion as well? In the future, when a self-admitted novice comes to your forum seeking help from those of you who are supposedly participating with a willingness to help someone who knows less than you do, if you find yourself frustrated with the course of conversation with that less-knowledgeable person, instead of taking a tone with them that is geared toward making them feel like an idiot, perhaps you could consider it just simply not engaging in the conversation with them any further. I feel like I did my very best to show you respect and appreciation throughout the course of our conversation. "Do unto others..."
I don't think any insult was intended but you have to look at it from the perspective of the many of use who help out on these sites, which to be honest, unfortunately we have to deal with many people who are as deeply rooted in their ignorance to outright stupidity as they are in their oversensitivity to what they want to take as negative criticism or an actual insult when none was actually intended let alone given.

Even then when a light insult is given it's mostly meant as a light slap and a suggestion to focus on what is being asked and or told with little more implied however that said if someone wants to get butt hurt and go all off topic there are a number of us who love to toss our very big dogs in that ring and go nuts with hard cold data and facts to let that person know that not everyone feels thinks or views the world the same as they do. :eek:

So with that what's your third lights voltage spiking to when it gets brighter being the solution to this whole issue may be as simple as adding two diodes and an LM317 regulator IC set up to work as a simple 120 mA constant current limiter. (4 total components involved)
 

Lestraveled

Joined May 19, 2014
1,946
But you need to keep the middle light from blinking with the turn signal.
...........the new 3rd brake light properly illuminates as a brake light, but it has a very slight pulsing action that corresponds with the blinker cycle from the turn indicator..............
When both the turn signal and the brake is applied, the turn signal light will dim slightly for the blinking function. The voltage does not go to zero. If the voltage does not drop too low then this circuit has a good chance of working.

Brake Light 2.jpg

@Farmaller48
You can test if this will work by connecting the relay you have across a turn signal. Turn the turn signal on and apply the brake. If the relay stays in the energized position then the circuit will work. (The diodes can be any 1N400X.)
 

crutschow

Joined Mar 14, 2008
25,669
.....................
BTW... may I offer you a suggestion as well? In the future, when a self-admitted novice comes to your forum seeking help from those of you who are supposedly participating with a willingness to help someone who knows less than you do, if you find yourself frustrated with the course of conversation with that less-knowledgeable person, instead of taking a tone with them that is geared toward making them feel like an idiot, perhaps you could consider it just simply not engaging in the conversation with them any further. I feel like I did my very best to show you respect and appreciation throughout the course of our conversation. "Do unto others..."
I admit that I became frustrated when you didn't do what I asked the first time, so apparently my answer expressed that. In never occurred that you were confusing a relay with a diode.
I find that many times someone will ask a question on this forum and then not follow the answer but go off on a tangent, so you may have taken some extra flak for things that others have also done.
But it was certainly not my intention to make you feel like an idiot and I apologize for that.

So if you can give me the results of your voltage measurement using a diode and capacitor, then I am more than happy to further help you with your problem.
But also, please pay more careful attention to the answers you get. ;)
 

crutschow

Joined Mar 14, 2008
25,669
When both the turn signal and the brake is applied, the turn signal light will dim slightly for the blinking function. The voltage does not go to zero. If the voltage does not drop too low then this circuit has a good chance of working.

View attachment 108710
...................
It would still seem the middle light will blink when both the turn-signal and the brake lights are operating.
Or am I missing something?
 

Lestraveled

Joined May 19, 2014
1,946
........................Or am I missing something?
A car has a separate light for braking and turn signals(per side). A trailer only has one light (per side). Trailer turn/stop light are not controlled directly from the cars turn/stop circuits. There is a "trailer conversion module" between the cars signals and the trailers signals. When both the turn signal and the brake is applied the trailer light will dim, instead of blink (on/off), to indicate brake and turn.

Here is an ad for one such module:
https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Curt/C56190.html
Quote:"Because most trailers run on a 2-wire system - wherein the brake and turn signals are carried on 1 wire - the signals from your vehicle may have to be converted to be compatible with your trailer's wiring. If your vehicle operates on a 3-wire system, which means that it has separate brake and turn signals, then those signals will need to be combined so that they run on 1 wire to properly activate your trailer's tail lights."

In other words, when you apply brakes and turn signal on a car the light pulsates because the brake light is on solid and the turn signal is blinking. The trailer conversion modules creates the same effect using only one bulb.
 
Last edited:

Thread Starter

Farmaller48

Joined Jun 30, 2016
25
I admit that I became frustrated when you didn't do what I asked the first time, so apparently my answer expressed that. In never occurred that you were confusing a relay with a diode.
I find that many times someone will ask a question on this forum and then not follow the answer but go off on a tangent, so you may have taken some extra flak for things that others have also done.
But it was certainly not my intention to make you feel like an idiot and I apologize for that.

So if you can give me the results of your voltage measurement using a diode and capacitor, then I am more than happy to further help you with your problem.
But also, please pay more careful attention to the answers you get. ;)
I sincerely appreciate your dignified and considerate reply, crutschow. It shows good character. And please know that I accept responsibility for contributing to the frustration factor on your end by having been less accurate than I should have been a couple of times. I promise to tighten up! ;) Thanks again for your offer to stay engaged in the conversation and provide the benefit of your knowledge.
 

crutschow

Joined Mar 14, 2008
25,669
A car has a separate light for braking and turn signals(per side). A trailer only has one light (per side). Trailer turn/stop light are not controlled directly from the cars turn/stop circuits. There is a "trailer conversion module" between the cars signals and the trailers signals. When both the turn signal and the brake is applied the trailer light will dim, instead of blink (on/off), to indicate brake and turn.

Here is an ad for one such module:
https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Curt/C56190.html
Quote:"Because most trailers run on a 2-wire system - wherein the brake and turn signals are carried on 1 wire - the signals from your vehicle may have to be converted to be compatible with your trailer's wiring. If your vehicle operates on a 3-wire system, which means that it has separate brake and turn signals, then those signals will need to be combined so that they run on 1 wire to properly activate your trailer's tail lights."

In other words, when you apply brakes and turn signal on a car the light pulsates because the brake light is on solid and the turn signal is blinking. The trailer conversion modules creates the same effect using only one bulb.
That's not my interpretation.
I would think that when the turn signal and brake are both on, then the trailer turn signal side will blink and the other side is on steadily.
 

Thread Starter

Farmaller48

Joined Jun 30, 2016
25
That's not my interpretation.
I would think that when the turn signal and brake are both on, then the trailer turn signal side will blink and the other side is on steadily.
crutschow is right. That is exactly how it works on the trailer I am dealing with. Brakes applied and turn signal on (R or L) results in one trailer tail light on steady (bright element in bulb illuminated) and bright element in the opposite side bulb flashing.
 

tcmtech

Joined Nov 4, 2013
2,867
As I have taken it his trailer uses the standard three wire type rear lighting setup which has one wire for left turn/left brake, one for right turn/right brake, and one for both sides running lights and if so Lestraveled's two diode two relay circuit is the simplest way to make things work.
 

Thread Starter

Farmaller48

Joined Jun 30, 2016
25
Unless I am reading @Lestraveled schematic wrong, wouldn't his solution also cause the cause the new middle 3rd brake light to illuminate when either of the turn indicators (R or L) is activated, with or without simultaneous brake application? I'm actually hoping I am wrong, as tying into the rear tail light circuits would be the easiest installation.
 
Top