Technical > Electronics > I need some brains to pick :)

I need some brains to pick :)

Hmmm maybe I put an resistor on the output for the parking lights Does it work for a LED like that? I've never tried.

reply to Subaru
It would help a lot to know what is is you are tying to accomplish, from your other post sounds like something automotive.

Since brightness is a function of current need to connect the LED to two different sources and control the current in each mode to obtain the desired brightness.

/tom

reply to Subaru
He's getting ready for winter and wants to make sure the snow plow can see him.

Sorry Subaru , I couldn't resist.

reply to tschmidt
turn signal/parking light it's dual brightness.

I figure if I find which one of the points of the bulb is for the parking lights (dim) I can add a resistor from that to the input to the Driver and from the other point for the turn signal (full brightness) I can connect that point direct to the driver so it can pass full current?

/Mike

reply to SparkChaser

reply to Subaru
It is not that simple unfortunately. The LED driver is going to try to provide the rated current regardless of the resistance. It won't be able to do so because of the limited voltage available which will cause your LED brightness to vary depending on the charge of your battery.

Two LED drivers with different current rating would be a better (but more expensive) option.
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if so I don't get it.. how could it supply it's rated current when it's output is going in a resistor? Are you saying it's brightness is going to go from stable (no resistor) to fluctuating up and down (resistor?)

Another thing is 350 mA and 700 mA i don't think that would be that much difference in light output?

Ah ok so then two drivers would be the simpler approach then?

reply to Subaru
I don't have much brain to share, but thought I'd sick my nose into this thread.

reply to Subaru
Hmm they are still saying it can be done :-/

»www.hidplanet.com/forums/showthr···st449095

reply to Subaru
Or another way is this..

»www.ledsupply.com/03023-d-e-350.php

has external or internal dimming control.. parking lights as it is now are not that bright at all maybe about the output of a dim nightlight..

It can be done with resistors, but an LED driver is much better.

The dimmable LED driver that you linked to 3021-D-E-#### is not perfect but suitable. The reason that I'm saying that it isn't perfect is that it will still require a bit of additional circuit to make it fully functional for your purpose.

The '-D-E' in the model number indicate DC voltage input and External dimming controls.
The -#### is the maximum output current (full intensity) which you need to choose based on the requirements of your LEDs.
You will need a 5KOhm potentiometer to set the dimmed output current and a relay to switch between maximum and dimmed intensity. You will also need two diodes to provide power to the LED driver from both high and low intensity power.
For the potentiometer use a 10-turn precision potentiometer (you don't need the precision, but those are less likely to change their value while driving). The relay can be any automotive relay with NO and NC contacts.

The exact circuit depends on how the current turn signal/parking light bulb is powered. Is the bulb common ground with two +12V contacts for high/low intensity or is it common +12V with two ground contacts ? Is it possible that both high and low intensity are active at the same time ? If so, what should the intensity of the LED be if both are active (probably bright) ?
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reply to Subaru
What (number) bulb are you trying to replace? I'm pretty sure I have already seen dual brightness LED's designed to replace Automotive tail lamps.

Not sure how they are doing it exactly, but I think they are using different brightness LEDS for the different filaments. So you put the low output LED's on the running lamps, and the high output LEDS on the brakes.

Here is one place..
»www.superbrightleds.com/cgi-bin/···2x19.htm

You can see they list 2 different current Draws for the 1157 dual filament replacement.

reply to leibold
So you are saying i would just need only one driver? Its a switches ground a single ground wire with two 12v leads. I'm not home now but how does the relay cause it to go to full bright?

reply to SparkChaser

reply to n1zuk

reply to SparkChaser

said by SparkChaser:

said by Subaru:

So you are saying i would just need only one driver? Its a switches ground a single ground wire with two 12v leads. I'm not home now but how does the relay cause it to go to full bright?

I also would look at that dimable drive before trying that kludge that the guy had with resistors. That was just trying o balance on a knife edge.