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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
Discussion Starter #1
I am in the process of putting together an HD light harness for my Outback, and I was thinking about an interesting idea that I'd like some input on.

I want to build the system so that I have a few second overlay where the low-beams remain on with the high beams. The purpose would be to prevent the "dead" flicker in a flash-to-pass scenario and extend the life of the low-beam bulbs. Flash-to-pass scenarios put a lot of stress on light bulbs, and considering it is the least offensive method of signaling another driver, I use it quite a lot.

It would also be useful should I ever decide to follow through with an OEM hybrid HID setup (3" projectors from the E39 BMW, and auto leveling sensors and motors from the EDM/JDM HID-Outback).

Since I am putting together an HD harness, what can I do to add that time delay in? I think a 1 to 2 second delay should be sufficient.
 

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2018 XT Touring CVT
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1,294 Posts
You could add a large 15V capacitor across the 12V input to the HID ballast, or a small 15V capacitor across the 12V relay coil for the system.
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
Discussion Starter #4
Beep, how much? I was hoping I could complete the project by raiding the small cache of electronics I've accumulated over the years.

Bash, a small 15V capacitor? How small?
 

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Premium Member
2004 Forester 4EAT
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5,462 Posts
Pricing
The price for the Time-Delay Relay is $24, plus any applicable shipping charges. If you purchase using the Paypal button below, it will calculate your shipping and should give you multiple options for shipping.
:biggrin:

Sounds like a cool toy to play with. Thinking about the dome light in my honda or something. I like that it's adjustable.
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
Discussion Starter #6
I was wondering if he'd sell me the one he didn't use.
 

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2018 XT Touring CVT
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1,294 Posts
You need to know the coil resistance to calculate the R times C time constant. You will need a RC time constant longer than the holding time you want, because the the coil can dropout at around 85% of voltage, and one time constant drops voltage to 63%. Watch your decimal point, and polarity.

Or you could experiment, (but do not experiment for polarity)

If you also need to have small spikes and large dips leveled off in the 12V power circuit, then you will need to go with the large capacitor in the power circuit.
 

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2016 Forester XT
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452 Posts
You could also use a simple transistor to keep the relay on for 'x' amount of time.
A simple RC circuit with a transistor can reliably keep the relay on for a brief amount of time. The advantage of using a transistor is that you can use much smaller values of capacitors and resistors which would also hold up better over time.

Here is an example circuit:
CircuitDB | Power-Off Time Delay Relay
 

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Premium Member
2015 XC diesel CVT
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4,053 Posts
Surely dip stays on if you flash-to-pass, and only turns off if you push the stalk to high?
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
Discussion Starter #11
Lows turn off during FTP, at least I am pretty sure they do...
 

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Premium Member
2015 XC diesel CVT
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4,053 Posts
best check. I've never seen a 4-lamp car that switched over on flash.
 

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Administrator
2018 2.5i Premium CVT
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18,949 Posts
YMMV with your Outback, but the Forester diagram does confirm that lows go off with flash to pass.
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
Discussion Starter #14
So it turns out that the low-beams DO remain on with the high beams during FTP. A time-delay might be nice for retrofit setups though, because FTP during a lights-off scenario still flash both sets of beams, and that WILL kill HID's.

But good, for my intents and purposes, I don't even need to worry.

I DID find out that the projectors in my lights are identical to the HID projectors in LHD Outbacks. Overseas, in HID equipped LHD countries, the entire headlight housing is the same between HID and non-HID. Pretty cool. Still, I would rather see about shoe-horning an auto-leveling 3" projector rather than trying to adapt auto-leveling to my 2.5" projectors.

I'd also be interested in seeing if an AFS system from a Lexus could be implemented. That'd be really neat.
 
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