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LED tail lamps

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Spokester Jerry Joseph
Allentown, PA, USA   USA
I posted this in the Spitfire/GT6 forum. Apologies if you've seen this already.

A friend of mine asked me to design an LED brake PCB for his TR6. Below are pics of the board. The board connects to the socket with a BAY15D bulb base on a wire pigtail. A couple of plastic clips hold the board in place on the existing reflector.

I tested the LED board against the standard 21W/5W brake/running light bulb and a Philips 1157LED(P21/5) red LED with 14V applied to each. Using a light meter at 4 FT, intensity measurements were done in LUX.

The LED brake PCB with red LEDs is considerably brighter than the standard bulb and the Philips LED unit. Compared to the standard bulb, the LED brake PCB is about 7x brighter on running lights and over 2.5x brighter on brakes.

Standard Bulb:
Running light current: 0.48A (6.72W)
Intensity @ 4FT: 4 LUX

Brake light current: 2.0A (28W)
Intensity @ 4FT: 48.4 LUX

LED brake PCB
Running light current: 0.08A (1.12W)
Intensity @ 4FT: 25.2 LUX

Brake light current: 0.33A (4.62W)
Intensity @ 4FT: 132.3 LUX

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ed.h Ed Hollingsworth
Omaha, Nebraska, USA   USA
Very nice job, Jerry. Is it series-parallel LEDs with limiting resistors, or something more exotic?

Ed

Spokester Jerry Joseph
Allentown, PA, USA   USA
In reply to # 1432839 by ed.h Very nice job, Jerry. Is it series-parallel LEDs with limiting resistors, or something more exotic?

Ed

Thanks Ed. You hit the nail on the head. The board is designed with 4 series LEDs with a resistor to set the current. The brake board shown has 48 LEDs thus 12 parallel strings of 4 LEDs. Since the operating voltage of the vehicle should be somewhat constant between 12.6V and 14-15V, the LED current does not vary that much and the LED brightness stays relatively constant. I don't have much experience with the electrical system of the TR6 but I assume the voltage will stay within 12.6-15V. If this is an incorrect assumption, maybe a different current limit solution is needed for the TR6.

Some LED solutions use voltage regulators to keep the current constant. I've avoided VRs because they concentrate power dissipation in a single component. For example, the LED brake board shown above burns less than 0.5A. If the minimum regulation voltage is 10V and maximum is 14V, the VR will burn 4V x 0.5A = 2W. Introducing this much power in a single component will result in a hot spot on the board.

On the LED brake board above, 12 large resistors are distributed evenly around the board to evenly dissipate the power. As such, the board still rises about 40C above ambient although it is quite constant across the board. A single VR burning 2W could cause a hot spot on the board of 60-80C rise over ambient.

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tomshobby Avatar
tomshobby Tom Smith
Windsor, Wisconsin, USA   USA
In reply to # 1407408 by dvcasano There are two bulbs used in the heater display that are not yet available in led.

www.classiccarleds.co.uk has them. I just got a pair of them today.



Tom Smith
1976 TR6
1974 Midget

Spokester Jerry Joseph
Allentown, PA, USA   USA
I finally built the first set of brake and rear turnsignal LED boards. I used quick connect spade connectors to eliminate the troubled bulb sockets.

I'm looking for a volunteer to try these out. What I will do is give someone a set of brake and turnsignals in return for installing them and taking some pics and post them here. I don't have a TR6 handy to try these out on so looking for someone to be my beta tester. Please contact me if you're interested.

Installing the boards should be pretty easy. The brake board slides onto the bulb reflector on the top then 2 bottom clips are turned sideways until the top clip is seated.


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Spokester Jerry Joseph
Allentown, PA, USA   USA
Installing the turnsignal is easier than the brake board. Each turnsignal board uses 2 identical frames which clip onto the reflector. Simply screw in the 4 screws and the board is installed. Connect the wires using the quick connect spade.


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Spokester Jerry Joseph
Allentown, PA, USA   USA
Aaron has stepped up to help by trying out a set of brake and turnsignal boards. He should have the lights this week so maybe we'll hear from him later.

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A. Bradley Aaron Bradley
Erwin, TN, USA   USA
1969 Jaguar E-Type 2+2 "The Jag"
1975 Triumph TR6 "The TR"
They arrived today. They're a pretty neat creation to look at. So far I've just plugged them in and made them illuminate.
They're really bright and project well. The turn signal board is really handy to have that load ballast built in. It blinks in unison with the front signal even though the front is still an incandescent bulb.
I might start a separate build thread on this soon but here's one picture to attach in the meantime.


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A. Bradley Aaron Bradley
Erwin, TN, USA   USA
1969 Jaguar E-Type 2+2 "The Jag"
1975 Triumph TR6 "The TR"
A little progress update:
I'm waiting on some lens gaskets and hardware to show up or else they would be done. Typical Brit car joke, "I am waiting on parts."
They fit pretty good with the nifty 3-D printed brackets and stainless hex screws. Here's a few pictures.

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A. Bradley Aaron Bradley
Erwin, TN, USA   USA
1969 Jaguar E-Type 2+2 "The Jag"
1975 Triumph TR6 "The TR"
Wow, They are a healthy bright. (Here's a little video which doesn't do them justice on this camera phone.) I can get better video soon. 'Just moved the TR into this "new" garage under construction.

A. Bradley Aaron Bradley
Erwin, TN, USA   USA
1969 Jaguar E-Type 2+2 "The Jag"
1975 Triumph TR6 "The TR"
In reply to # 1442819 by A. Bradley Wow, They are a healthy bright. (Here's a little video which doesn't do them justice on this camera phone.) I can get better video soon. 'Just moved the TR into this "new" garage under construction.
The video wouldn't load here. I'll post it under the photo/video thread.

Spokester Jerry Joseph
Allentown, PA, USA   USA
I've been working on reverse LED boards for the TR6. The reverse board is more difficult than the brake and turnsignal which both have reflectors pointed directly towards the car behind for maximum light intensity.

The TR6 reverse lens has a convex focusing section opposite the bulb as seen below.

The pic below is a shadow on the ceiling with the lens on a table about 3-4 foot from the ceiling. The tape is directly opposite from the lens and would be horizontal from the lens on the car. In the pic, ground would be at the bottom of the pic.

This convex focus section does a good job with the standard bulb. The pic below with the bulb intensity should not be compared with LED pics since I powered the bulb with my HO power pack and it couldn't drive the 2A @ 14V needed to power the bulb.


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Spokester Jerry Joseph
Allentown, PA, USA   USA
To simulate LEDs in the reverse lens, I used a reverse LED board for a 911 as shown below.

First I wanted to see what the top 1/2 of the lens would do with LEDs behind it. This would be the right side of the previous lens pic.

For this pic, the convex focusing section was blocked off from light so all the light is from the top "louvered" section. Notice most of the light energy is focused downward behind the car. I estimate this would shine on the pavement about 5 feet behind the car and quite useless for anything. Some light does shine rearward towards the tape and car behind, but most is wasted illuminating the pavement directly behind the car.


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Spokester Jerry Joseph
Allentown, PA, USA   USA
This time I put the LEDs behind the convex focusing section. Now the light is directed behind the car although the lens provides no dispersion of the LED light. In the pic, there are 3 rows of LEDs which can be seen by the 3 bright spots. The LEDs behind the convex focusing section have most of their light pointed directly towards the car behind.


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A. Bradley Aaron Bradley
Erwin, TN, USA   USA
1969 Jaguar E-Type 2+2 "The Jag"
1975 Triumph TR6 "The TR"
Hey Jerry, That's a really neat and interesting experiment test there with the optics. Even with most of the light aimed down shortly behind the car, it may still be okay to use and work. In person it might be just as good or better than conventional bulbs. Reverse light usage and function on these cars seems to be minuscule for the most part. But LED's are excellent!
'Looking forward to using and showing your LED boards. So far, I've showed them off to some friends and family. They've all been impressed.

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