[BAC5.2]

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.

 

[thebeephaha]

The time delay relay I used in one of my projects could work. http://www.subaruforester.org/vbulletin/f85/need-help-new-relay-design-diagram-67007/#post742308

I ended up not using it because I ran into other issues and got lazy and went a different route but you might be able to make it work for your purpose.

 

[bashfulbernie]

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.

 

[BAC5.2]

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?

 

[jgrote]

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.

 

[BAC5.2]

I was wondering if he'd sell me the one he didn't use.

 

[thebeephaha]

I was wondering if he'd sell me the one he didn't use.

I was actually going to hold onto it if I ever get the time to rewire and plan out my relay better.

Though I can say, the thing works great, dual trigger inputs, low and high side switching, adjustable time delay.

 

[bashfulbernie]

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.

 

[ZapWizard]

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

 

[dpm]

Surely dip stays on if you flash-to-pass, and only turns off if you push the stalk to high?

 

[BAC5.2]

Lows turn off during FTP, at least I am pretty sure they do...

 

[dpm]

best check. I've never seen a 4-lamp car that switched over on flash.

 

[bbottomley]

YMMV with your Outback, but the Forester diagram does confirm that lows go off with flash to pass.

 

[BAC5.2]

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.