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Discussion Starter · #1 · (Edited)
Recently installed H9 lamps into the H11 low beams on my XC. Being Canada, land of DRLs, the H9 low beams are a bit excessive to use as DRLs. I'd like to extend the life of the lamps by operating them at a reduced voltage and having photocontrol to automatically turn them to 100% at night so they can be used as lowbeams.

What I'm thinking:
- Only having photocontrol with the headlamp switch at 0. Parking lights and Lowbeam will still be manual "ON" on the switch.
- Install a SPDT relay controlled by a photocell.
- Install a high wattage resistor (to be calculated) on the NC contact, straight circuit on the NO.

Going to visit my favourite electronics parts store for parts. Looking for suggestions or comments on this.

Cheers.
 

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that's gonna be one hell of a resistor, and it's gonna get hot.

if I were to undertake something like this I'd probably look at a buck converter to drop the voltage.
more efficient, and with a headlamp element I don't think you'd ever notice the switching.

Another possible option, what about a city lamp in the headlamp housing? then you're not using the headlamp at all and you can use a 5 or 10W LED as your DRL.
Then you could simply tap into the headlamp wire to turn off the DRL LED. no monkeying with the headlamp harness or it's operation. Assuming that you can defeat the factory DRL stuff without the car freaking.
 

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Discussion Starter · #6 · (Edited)
- Adjustable Photocell with adjustable time delay relay
- SPDT Relay PN: DK4901 w/ DK4922Wire
- Resistors
- Add-a-circuit - for the control circuit (may just tap off the current one for my boost gauge)

Don't have an exact circuit Voltage (will get the meter out to check), but let's assume 14VDC is operating voltage. Unsure how dim the lamps will be at any given voltage, so I'll bench test a few to see what I like.

Of the resistors listed, using 14V, voltage at lamp would be.
0.33ohm = 12.2V
0.5ohm = 11.4V
1ohm = 9.6V
2ohm = 7.35V
 

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This thread fascinates me and is a great idea. Keep updating us on what you find and what you do, with pictures. I'm certain this is what contributes to the hazing of the stupid plastic lenses on my s60. If they weren't subject to heat all the time, they would last longer as crystal clear, and yes- the bulbs would last a lot longer.
 

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Discussion Starter · #8 ·
This thread fascinates me and is a great idea. Keep updating us on what you find and what you do, with pictures. I'm certain this is what contributes to the hazing of the stupid plastic lenses on my s60. If they weren't subject to heat all the time, they would last longer as crystal clear, and yes- the bulbs would last a lot longer.
Just brainstorming for now, don't know when I'll get the time to figure this out. Have bigger fish to fry such as my AWD issue (have the parts, don't have a lift and the time).
 

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Discussion Starter · #9 · (Edited)
Found this:
Photocontrol and Time Delay Relay

This Photo relay has both NO and NC contacts. I can wire it so that the NC(default) circuit is 100% Lowbeam and NO can be the dimming circuit in case the circuit fails lows will be 100%, and this way all I'd need to do to manually override the photo control is disconnect the powersupply to the relay.

Got to figure out how I can make this work with the factory light switch. Also thinking I'll need one SPDT relay and one resistor per headlight near the headlight. I'd also need to fish one wire (control circuit) through the firewall.
 

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- Adjustable Photocell with adjustable time delay relay
- SPDT Relay PN: DK4901 w/ DK4922Wire
- Resistors
- Add-a-circuit - for the control circuit (may just tap off the current one for my boost gauge)

Don't have an exact circuit Voltage (will get the meter out to check), but let's assume 14VDC is operating voltage. Unsure how dim the lamps will be at any given voltage, so I'll bench test a few to see what I like.

Of the resistors listed, using 14V, voltage at lamp would be.
0.33ohm = 12.2V
0.5ohm = 11.4V
1ohm = 9.6V
2ohm = 7.35V
figure on losing 20% of the lumens for every volt dropped as a rule of thumb for halogen.
 

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Discussion Starter · #11 ·
OK, so I'm looking for 400-500 lumens. According you your estimate, 8-9VDC should do that?

Was trapped in the car (kid asleep) so I took a look at the lighting switch, which is a module that I cannot directly tap into the switch, but I did notice an open space beside the dimmer that I could mount toggle switch that would mount cleanly. Kind of takes away from the "auto, parking lights, manual on" control that I wanted, but should still work well. Just means auto is always on when the switch on, and off when it's not.
 

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I'd think that 8-9v is probably a good starting point.

doing some research it looks like the OEMs are using PWM to dim them. Similar to what a buck converter would do.
I'm honestly not sure how that would affect the life of the bulb though. I know that my mom's VW eats bulbs on the regular, and that probably has something to do with it.

I'd still really consider just taking the easy way out and modding the headlamp assembly to have an LED DRL in it like a city lamp, then you could proceed with your NC/NO relay plan so they turn off when you turn on the headlamps. Actually I'd probably tie them into a parking lamp, that way they would turn off with the parking lamps like a lot of the domestic OEMs have them set up.
 

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Discussion Starter · #13 ·
I have a PWM kicking around, but I'd rather use a resistor since the lamp circuit is also tied up with the CANBUS to eliminate the possibility of a false error.

I guess some high intensity LED could be installed in the parking lights to be used as DRLs, but I'd like the colour and look to kind of remain OE. I do have access to some @ 3000k and 4100k, I'll give them a shot. Have the relay switch between parking lamps and low beams (I know could just switch between parking lamps manually, but I want this to be automatic)
 

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Discussion Starter · #15 ·
Well if you really want you could switch off the DRLs in VIDA then hardwire a circuit to the parking lights, then manually switch to lows when needed. The parking lamps would be on all the time unless you install a relay somehow.
 

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Well if you really want you could switch off the DRLs in VIDA then hardwire a circuit to the parking lights, then manually switch to lows when needed. The parking lamps would be on all the time unless you install a relay somehow.
My thoughts were to install an LED in the headlamp housing. Tap into something that's keyed 12V, run that to 87A NC contacts, then trigger the relay from the parking lamp circuit.

On when you start the car, off when the parking lamps turn on.
 

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Discussion Starter · #18 ·
My thoughts were to install an LED in the headlamp housing. Tap into something that's keyed 12V, run that to 87A NC contacts, then trigger the relay from the parking lamp circuit.

On when you start the car, off when the parking lamps turn on.
I understand, but I'm unsure how you picture another LED in the housing. Within the reflector, or something like a strip under/over the reflectors.

The parking lamp itself is in a good location that light emitted from it would be reflected in the low beam reflector making it more visible.
 
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