#282703 - 08/06/2006 03:20
Headlight sense night dimming problem (voltage too low?)
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new poster
Registered: 25/05/2006
Posts: 11
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My headlights-on voltage is around +11V. The sense line for night dimming is listed at +12V to activate. Night dimming does not work for me. Am I right to suspect that the voltage is not quite high enough to activate the sensor?
At some point, I am probably going to wire something up to work around this (opto-coupler gating constant-power to headlight sense wire, controlled by car's headlight voltage), but in the mean time, can anyone confirm/refute this interpretation of the problem?
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#282704 - 08/06/2006 03:22
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Bernz]
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carpal tunnel
Registered: 20/12/1999
Posts: 31597
Loc: Seattle, WA
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I can't imagine it would be THAT picky. Just to be sure, you already checked all this, right?
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#282705 - 08/06/2006 03:27
Re: Headlight sense night dimming problem (voltage too low?)
[Re: tfabris]
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Registered: 25/05/2006
Posts: 11
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Wow, awesome response time! Actually, although I'd read a good deal of the FAQ, I hadn't yet got to the dimmer-related stuff, and I hadn't thought to check there yet. So, I will definitely go over all that stuff first. Thanks for the tip!
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#040103342 (MK2a: 16MB, 20GB) - Glee!!
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#282706 - 12/06/2006 01:07
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Bernz]
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pooh-bah
Registered: 12/01/2002
Posts: 2009
Loc: Brisbane, Australia
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Is it 11V DC though? Some newer cars (e.g. VW) have a PWM signal for dimmer since the signal passed to the stereo is more than just on off. i.e. the dash brightness control also controls the brightness of the factory stereo's backlighting. The empeg doesn't have this. It simply has an on/off setting.
If you've measured it with a multimeter on DC a switching signal it could quite rightly measure 11V. A poor man's check for a switching signal is to put the multimeter on AC volts. If it reads non-zero then it's likely it's a pulsing signal.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)
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#282707 - 12/06/2006 01:10
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Shonky]
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carpal tunnel
Registered: 20/12/1999
Posts: 31597
Loc: Seattle, WA
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The empeg should properly handle a PWM signal, though. And I'm still pretty sure that it'd stil work with 11v.
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#282708 - 12/06/2006 01:27
Re: Headlight sense night dimming problem (voltage too low?)
[Re: tfabris]
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pooh-bah
Registered: 12/01/2002
Posts: 2009
Loc: Brisbane, Australia
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Quote:
The empeg should properly handle a PWM signal, though. And I'm still pretty sure that it'd stil work with 11v.
Why would it handle a PWM signal properly? It's not designed to. It samples a signal at a particular rate (probably fairly slowly). At best it will probably alternate between active and inactive depending on whether it's sampled with the signal high or low.
I agree though that 11VDC should be heaps to be detected.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)
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#282709 - 12/06/2006 01:31
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Shonky]
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pooh-bah
Registered: 12/01/2002
Posts: 2009
Loc: Brisbane, Australia
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I think I know what the problem might be. The empeg has no definition of dimmer line active or not really. Rather it just stores two seperate dimmer settings for each state of the dimmer line. I would guess you have both set to 100% so it appears the dimmer isn't working.
You need to adjust the dimmer from the menu, while the dimmer line is actually active.
Just realised that that's what Tony linked to in the FAQ. Thought I'd post it anyway.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)
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#282710 - 12/06/2006 01:38
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Shonky]
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carpal tunnel
Registered: 20/12/1999
Posts: 31597
Loc: Seattle, WA
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Quote:
Why would it handle a PWM signal properly? It's not designed to.
I remember that being something they compensated for in software, during the betas for the 1.0 software. It's possible to handle that sort of thing in software.
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#282711 - 12/06/2006 01:44
Re: Headlight sense night dimming problem (voltage too low?)
[Re: tfabris]
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pooh-bah
Registered: 12/01/2002
Posts: 2009
Loc: Brisbane, Australia
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Quote:
Quote:
Why would it handle a PWM signal properly? It's not designed to.
I remember that being something they compensated for in software, during the betas for the 1.0 software. It's possible to handle that sort of thing in software.
Not really that easy in software. It's merely a digital input to the processor. At best you could have some kind of filtering/averaging and detect that if x out of every y samples or higher are active, then consider the input active. Creates a delay in detection of at best x samples and up to y samples and also doesn't cover the case where the sample rate and the PWM rate conincide (by some factor).
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)
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#282712 - 12/06/2006 11:12
Re: Headlight sense night dimming problem (voltage too low?)
[Re: tfabris]
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carpal tunnel
Registered: 29/08/2000
Posts: 14493
Loc: Canada
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Quote:
The empeg should properly handle a PWM signal, though.
Nope. The software is just a simple on/off detection, at present. Dunno about the hardware side, though.
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#282713 - 13/06/2006 13:48
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Shonky]
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carpal tunnel
Registered: 08/06/1999
Posts: 7868
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I'd have to double check my wiring, but I believe my empeg is hooked up to a PWM signal for the sensing, as the stock stereo paid attention to that line as a dimmer indicator along with the rest of the dash. The installer may have found a solid 12v line though in the dash and used it, it's been a couple years since I saw the spagetti mess of wiring.
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#282714 - 13/06/2006 22:52
Re: Headlight sense night dimming problem (voltage too low?)
[Re: Shonky]
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new poster
Registered: 25/05/2006
Posts: 11
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Quote:
I think I know what the problem might be. The empeg has no definition of dimmer line active or not really. Rather it just stores two seperate dimmer settings for each state of the dimmer line. I would guess you have both set to 100% so it appears the dimmer isn't working.
You need to adjust the dimmer from the menu, while the dimmer line is actually active.
Just realised that that's what Tony linked to in the FAQ. Thought I'd post it anyway.
Yep, I'm pretty sure that was the problem, because I hadn't changed the dimmer setting yet before assuming there was a problem. I will hook it back up and post back with results.
In the meantime, I thought it would be cool to build a PWM-driver whose frequency is controlled by a photocell for automatic variable dimming, but I kinda figured the sense line was tied to software... ah well.
Edited by Bernz (13/06/2006 22:54)
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#282715 - 20/06/2006 19:02
Re: Headlight sense night dimming problem (voltage too low?)
[Re: mlord]
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carpal tunnel
Registered: 19/05/1999
Posts: 3457
Loc: Palo Alto, CA
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ISTR it does handle a PWM signal; the player software requires no high levels on the line for a certain time (a second? half a second?) to decide it's actually low.
Hugo
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#282716 - 20/06/2006 19:14
Re: Headlight sense night dimming problem (voltage too low?)
[Re: altman]
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carpal tunnel
Registered: 29/08/2000
Posts: 14493
Loc: Canada
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Quote:
ISTR it does handle a PWM signal; the player software requires no high levels on the line for a certain time (a second? half a second?) to decide it's actually low.
Okay, so this may work for an "active low" sense, but maybe not not the other way round.
A similar method is used by Hijack for the button_LED dimmer sense.
Cheers
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