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> LED Foglight Project
Spoke
post Apr 13 2019, 08:45 AM
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Jerry
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The design of an early foglight LED board has begun. mepstein sent me a couple of foglight fixtures to use to design the board. 2 main issues are fitment and heat dissipation. If things work out ok the design should be able to be re-laid out for the later square foglight.

The board will have 8 Cree XP-G3 high power surface mount LEDs with 350ma current each. These will burn about 1W of power with a total power dissipation expected to be less than 10W. Hopefully these will be almost as bright as a headlight.

Each LED will have its own focusing lens. The lenses are Carclo 10192 elliptical 20mm lenses. The light pattern for the 10192 lens is shown below.

Attached Image

This is the spectral dispersion for the lens.

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orthobiz
post Apr 17 2019, 12:26 PM
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Why do these need a converter when your other taillight/sidemarker lights don't?

Paul
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Spoke
post Apr 17 2019, 06:44 PM
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QUOTE(orthobiz @ Apr 17 2019, 02:26 PM) *

Why do these need a converter when your other taillight/sidemarker lights don't?

Paul


There's a couple of reasons for using a converter on these lights. First the current is a lot higher for each LED. 350ma per LED for this foglight vs 20ma per LED for brake/turnsignals. Thus the current limiting resistor for brakes doesn't burn that much power. Total power burned by all the current limiting resistors on the brakes is less than 1W and it is evenly distributed across the board.

The brakes/turnsignals have 56 LEDs configured as 16 strings of 4 LEDs in series. 4 red or amber LEDs only need about 2V each or 8V total to turn on. In the foglight there are 8 LEDs total in one series string. White LEDs need about 3+ volts to turn on. Thus the total voltage of the string is over 24V and the need for a dc-dc converter.

With resistors providing current limit on the brakes/turnsignals, there is some brightness difference between battery voltages of 12V to 14V although it is not so noticeable.

For the foglights the light output must be constant for all operating voltages. This converter will turn on when the applied voltage is about 9V and the LED current will remain constant over the entire battery voltage range. This way there will be no flickering or dimming if the battery voltage is high or low.

In the 356 front light there were 19 LEDs in series and the voltage needed to drive that stack was over 50V.
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Morrie
post Apr 17 2019, 07:58 PM
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Ideally you would have a converter with no resistors running in constant current mode rather than constant voltage. Or at least that’s how the growers are doing it.
QUOTE(Spoke @ Apr 17 2019, 07:44 PM) *

QUOTE(orthobiz @ Apr 17 2019, 02:26 PM) *

Why do these need a converter when your other taillight/sidemarker lights don't?

Paul


There's a couple of reasons for using a converter on these lights. First the current is a lot higher for each LED. 350ma per LED for this foglight vs 20ma per LED for brake/turnsignals. Thus the current limiting resistor for brakes doesn't burn that much power. Total power burned by all the current limiting resistors on the brakes is less than 1W and it is evenly distributed across the board.

The brakes/turnsignals have 56 LEDs configured as 16 strings of 4 LEDs in series. 4 red or amber LEDs only need about 2V each or 8V total to turn on. In the foglight there are 8 LEDs total in one series string. White LEDs need about 3+ volts to turn on. Thus the total voltage of the string is over 24V and the need for a dc-dc converter.

With resistors providing current limit on the brakes/turnsignals, there is some brightness difference between battery voltages of 12V to 14V although it is not so noticeable.

For the foglights the light output must be constant for all operating voltages. This converter will turn on when the applied voltage is about 9V and the LED current will remain constant over the entire battery voltage range. This way there will be no flickering or dimming if the battery voltage is high or low.

In the 356 front light there were 19 LEDs in series and the voltage needed to drive that stack was over 50V.

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Posts in this topic
Spoke   LED Foglight Project   Apr 13 2019, 08:45 AM
Spoke   The LEDs will be connected in series and driven by...   Apr 13 2019, 08:51 AM
Spoke   This is what the board looks like right now. It ma...   Apr 13 2019, 08:58 AM
mepstein   I don't understand any of this but it sure loo...   Apr 13 2019, 12:16 PM
StratPlayer   Will you be making these for the rectangle style f...   Apr 13 2019, 01:34 PM
Spoke   Will you be making these for the rectangle style ...   Apr 14 2019, 05:57 AM
Spoke   Will you be making these for the rectangle style ...   May 9 2019, 07:24 PM
mepstein   [quote name='StratPlayer' post='2704950' date='Ap...   May 9 2019, 07:37 PM
DRPHIL914   [quote name='StratPlayer' post='2704950' date='Ap...   May 10 2019, 08:13 AM
Luke M   I'd be in for an early set once you get them d...   Apr 13 2019, 02:11 PM
914-300Hemi   Looks great Spoke.   Apr 14 2019, 06:05 AM
Spoke   This is the fixture I'll use to size the board...   Apr 14 2019, 06:09 AM
Spoke   I printed the PCB front and bottom sides since I c...   Apr 14 2019, 06:15 AM
Spoke   With the spacer attached, now the PCB can sit squa...   Apr 14 2019, 06:21 AM
Tbrown4x4   I'm totally supporting this. I drive at night ...   Apr 14 2019, 07:09 AM
mepstein   I'm totally supporting this. I drive at night...   Apr 14 2019, 10:45 AM
mb911   Really excited for this although currently I only ...   Apr 14 2019, 09:27 AM
mepstein   Really excited for this although currently I only...   Apr 14 2019, 10:33 AM
Tbrown4x4   Good to know! I think I have these on an Amazo...   Apr 15 2019, 05:02 AM
orthobiz   This is great, thanks. I posted some lens pictures...   Apr 15 2019, 03:31 PM
Spoke   This is great, thanks. I posted some lens picture...   Apr 15 2019, 07:49 PM
Mike Bellis   Why not mount the power supply remote in an IP65/6...   Apr 15 2019, 07:22 PM
Spoke   Why not mount the power supply remote in an IP65/...   Apr 15 2019, 07:53 PM
Spoke   OK, the PCBs have been sent to the fab house. Shou...   Apr 16 2019, 09:12 PM
FlacaProductions   I deal with color temp every day. 3200 is tungsten...   Apr 16 2019, 11:08 PM
windforfun   I deal with color temp every day. 3200 is tungste...   Apr 23 2019, 04:02 PM
orthobiz   Why do these need a converter when your other tail...   Apr 17 2019, 12:26 PM
Spoke   Why do these need a converter when your other tai...   Apr 17 2019, 06:44 PM
Morrie   Ideally you would have a converter with no resisto...   Apr 17 2019, 07:58 PM
Spoke   Ideally you would have a converter with no resist...   Apr 19 2019, 02:34 PM
orthobiz   [quote name='orthobiz' post='2706213...   Apr 17 2019, 08:06 PM
914forme   PDBs going to be green or black in the final versi...   Apr 17 2019, 08:22 PM
Spoke   PDBs going to be green or black in the final vers...   Apr 18 2019, 08:02 PM
ClayPerrine   [quote name='914forme' post='2706330' date='Apr 1...   Apr 19 2019, 02:40 PM
Mblizzard   I will be in for a set of squares. Last lights on...   Apr 18 2019, 12:18 PM
eric9144   This is pretty awesome and totally something I...   Apr 18 2019, 01:57 PM
76-914   :popcorn:   Apr 19 2019, 07:16 AM
ValcoOscar   Same here... :popcorn: :popcorn: :popcorn: I s...   Apr 19 2019, 07:33 AM
DRPHIL914   thanks for taking this on! I asked about this ...   Apr 19 2019, 07:38 AM
Spoke   I agree about the comments on color, you don...   Apr 19 2019, 02:39 PM
Spoke   To reduce component and assembly cost, I'm loo...   Apr 22 2019, 06:59 PM
Al Meredith   would it make sense to have two levels, one for ru...   Apr 23 2019, 03:39 PM
Spoke   would it make sense to have two levels, one for r...   Apr 24 2019, 06:50 AM
Chi-town   Just a thought but if you're using a LED chip ...   Apr 24 2019, 09:25 AM
Spoke   Just a thought but if you're using a LED chip...   Apr 24 2019, 11:11 AM
Spoke   Have the PCBs in hand. Will assemble the first boa...   Apr 26 2019, 08:01 AM
Spoke   Here's the PCB under the glass. It will be int...   Apr 26 2019, 08:03 AM
DRPHIL914   :popcorn: Looking good! Cant wait to see the...   Apr 26 2019, 08:06 AM
Spoke   Things like this happen when you set the temperatu...   Apr 29 2019, 01:55 PM
mepstein   Things like this happen when you set the temperat...   Apr 29 2019, 02:14 PM
Spoke   With the correct settings, the oven worked fine. ...   Apr 29 2019, 03:06 PM
Spoke   All lit up with LED lenses. Won't be able to c...   Apr 29 2019, 03:10 PM
Spoke   Printed a jig to drill the heat sink for tapping. ...   Apr 29 2019, 03:13 PM
Spoke   Here's the light pattern with 0.5A per LED on ...   Apr 29 2019, 03:43 PM
Spoke   The glass lens fits nicely with the printed spacer...   Apr 29 2019, 03:46 PM
Spoke   Here's the light pattern with 0.5A with the gl...   Apr 29 2019, 03:48 PM
Spoke   Redesigned the spacer rings so the boards can scre...   Apr 29 2019, 04:49 PM
Spoke   These are the wrong screws. These are #4 x 5/16 wh...   Apr 29 2019, 04:51 PM
Spoke   The first fully built up PCB. Somehow I managed to...   Apr 30 2019, 04:10 AM
Spoke   Started doing some burn in on the first unit. Will...   Apr 30 2019, 04:15 AM
jkb944t   Started doing some burn in on the first unit. Wil...   Apr 30 2019, 06:15 AM
DRPHIL914   Looks great!!! Cant wait to get a set...   Apr 30 2019, 05:54 AM
Spoke   Burned in the prototype for about 20 hours this we...   May 3 2019, 07:59 PM
Spoke   The metal clips will need to be made for each unit...   May 3 2019, 08:01 PM
Spoke   The PCB fits nicely in the case. Will run this for...   May 3 2019, 08:04 PM
Spoke   Not sure how to connect up to the existing wires y...   May 3 2019, 08:07 PM
ClayPerrine   http://www.914world.com/bbs2/uploads_offsite/i.kym...   May 3 2019, 08:50 PM
Chi-town   Can you take a pic of the light output on a wall f...   May 3 2019, 09:58 PM
Spoke   This is the light pattern projected on the ceiling...   May 4 2019, 05:42 AM
Spoke   Got the prototype lit up in the foglight enclosure...   May 5 2019, 02:13 PM
Spoke   Compared the output of the LED foglight to the fog...   May 6 2019, 09:52 PM
Spoke   The driver side foglight is covered up and the LED...   May 6 2019, 09:57 PM
Chi-town   That upper washout will be blinding to oncoming tr...   May 6 2019, 10:48 PM
Luke M   Would the fog light lens make a difference ? I do ...   May 7 2019, 07:43 AM
Spoke   Would the fog light lens make a difference ? I do...   May 7 2019, 05:21 PM
mepstein   Would the fog light lens make a difference ? I d...   May 7 2019, 05:28 PM
Spoke   [quote name='Luke M' post='2711759' date='May 7 ...   May 7 2019, 05:35 PM
mepstein   [quote name='mepstein' post='2711910' date='May 7...   May 7 2019, 06:01 PM
Spoke   I have two early sets I can send you. One questi...   May 7 2019, 06:21 PM
mepstein   I have two early sets I can send you. One quest...   May 7 2019, 06:45 PM
JeffBowlsby   Open the housing and disconnect the wires! No...   May 7 2019, 06:55 PM
worn   Open the housing and disconnect the wires! N...   May 7 2019, 07:54 PM
Spoke   Open the housing and disconnect the wires! N...   May 8 2019, 08:02 PM
Spoke   I'm working on a 911 variant of the foglight l...   May 9 2019, 07:12 PM
mepstein   Early ones are on their way. They are in much bett...   May 9 2019, 07:23 PM
Chi-town   Sorry no fogs on my 75'   May 9 2019, 08:48 PM
Chi-town   Are you going to try different optics or main lens...   May 10 2019, 08:32 AM
mepstein   Are you going to try different optics or main len...   May 10 2019, 08:42 AM
Luke M   [quote name='Chi-town' post='2712683' date='...   May 10 2019, 10:31 AM
Spoke   Are you going to try different optics or main len...   May 10 2019, 02:54 PM
Chi-town   There's a big difference between an old 35 wat...   May 10 2019, 12:09 PM
Spoke   Put the board into one of the fixtures provided by...   Jun 1 2019, 06:52 AM
mepstein   Put the board into one of the fixtures provided b...   Jun 1 2019, 07:02 AM
Spoke   The early lenses are at least 5mm deeper than the ...   Jun 1 2019, 06:53 AM
Spoke   Does anyone make the rubber gasket that goes aroun...   Jun 1 2019, 07:04 AM
Chi-town   914 Rubber makes them   Jun 1 2019, 08:13 AM
Spoke   914 Rubber makes them Thanks. I ordered 2 sets....   Jun 1 2019, 09:13 AM
Mikey914   Ill make sure they get cross listed. We also ma in...   Jun 1 2019, 09:54 PM
Spoke   Finally got the 2nd 914 foglight assembled. This d...   Jun 11 2019, 07:44 PM
Spoke   Here's the 911 foglight fitted in the lens. Th...   Jun 11 2019, 07:47 PM
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