# Faster Head Unit Boot or Always ON.



## rocketsarefast (Apr 28, 2015)

Many newer head units have very long boot times, often 20-40 seconds. I would like to do one of three solutions.

1. Wire the head unit to be always on. The amps will turn off when the car turns off, but the head unit will remain powered, even overnight. This will obviously drain the battery, maybe in just 2 hours making this solution impossible.

2. I have noticed that when I unlock my car, the dome light turns on. Perhaps I can wire the dome light to the head unit to get the boot up process started sooner, as I am sitting down instead of after turning the key. Again the amps would still be switched by ignition power. Obviously this would make the head unit turn off when the dome light then goes off. However, I can build a small arduino circuit and write some software to sense the dome light and turn on the head unit, leaving it on until it senses the ignition turn on, and then off later.

3. Some other more awesome solution such that when I glare sternly at my car from across the parking lot, the head unit starts booting.


Has anyone tried anything like this? Any suggestions? I am also considering putting a tablet in the dash because they can go to sleep, and wake up instantly. I am less interested in this option, but still open minded.


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## schmiddr2 (Aug 10, 2009)

Assuming you drive the car twice a day every day and it takes 30 seconds to boot the HU that is 6 hours of wait time a year. I would just wait and let the car warm up for an extra 30 seconds, unless you want to add a remote start; all my cars get them because the HU is on and electronics warmed up by the time I get in the car. To have the door switch start the HU would save a few seconds, not worth the hassle. You could just use a cheap alarm to do the job without doing anything else.


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## SkizeR (Apr 19, 2011)

another problem with your dome light idea, is that as soon as you turn the key all power is lost for a split second. itll have to reboot again


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## rocketsarefast (Apr 28, 2015)

SkizeR said:


> another problem with your dome light idea, is that as soon as you turn the key all power is lost for a split second. itll have to reboot again


Yeah, it would definitely require an arduino or something wired straight to the battery to hold the ignition lead of the stereo ON during start. Not hard since i regularly program arduino chips to do various mundane logic things like this. 

And on that thought, why is the stereo always turned off during crank on cars? I find it hard to believe that a stereo pulling a couple amps is going to cripple the 400 cranking amps used to start the engine. a big aftermarket amp playing loud music, yes, will hinder the starter motor, but the stock stereos do this too. The factory could get really clever and just disable the output amp section of the head unit during crank, and leave the digital stuff running.


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## rocketsarefast (Apr 28, 2015)

schmiddr2 said:


> Assuming you drive the car twice a day every day and it takes 30 seconds to boot the HU that is 6 hours of wait time a year. I would just wait and let the car warm up for an extra 30 seconds, unless you want to add a remote start; all my cars get them because the HU is on and electronics warmed up by the time I get in the car. To have the door switch start the HU would save a few seconds, not worth the hassle. You could just use a cheap alarm to do the job without doing anything else.


An alarm system with remote start is a pretty good solution, but less DIY  And yes, it would take me more than 6 hours to build and program this dome light digital relay thing, so it probably IS more work than it is worth. I will look into alarms with remote start and see what I can find. It just didn't have the "neat" factor. Thank you.


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## warbital (Feb 5, 2013)

I say go for option 2 but instead of using an arduino this can be accomplished with a relay. 
If you use a capacitor on the power line from the dome light it will latch the relay for as long as the cap holds enough power for the relay. Obviously you would need a diode to stop the dome light from draining the cap and small resistor to set how long it takes for the cap to discharge.

I'd put up image but I don't have enough posts here yet.

You would need one more diode on the accessory line coming into the radio to stop this relay from powering all the accessories when the dome light is on but you'd have to do that with the arduino too.


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## rocketsarefast (Apr 28, 2015)

warbital said:


> I say go for option 2 but instead of using an arduino this can be accomplished with a relay.
> If you use a capacitor on the power line from the dome light it will latch the relay for as long as the cap holds enough power for the relay. Obviously you would need a diode to stop the dome light from draining the cap and small resistor to set how long it takes for the cap to discharge.
> 
> I'd put up image but I don't have enough posts here yet.
> ...



You know, that might actually work. I feel a little dumb for not thinking of that. Two big diodes and a 470uF cap might solve everything. I might not even need the relay if the ignition wire of the head unit pulls very low current. This will be the first thing I try when I start installing the head unit. I even have those parts already. Thank you very much. Man I feel dumb.


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## Theslaking (Oct 8, 2013)

I have a small (2"x3"x5") battery with an isolator that prevents the stereo from draining the car battery. Cost me about $45 for both. It will run the radio for a few hours loud so I imagine with doing nothing but being on it would last a while. I only bought it because I switch headunits in my work truck 4 or 5 times a year and get sick of starting over with the dsp. Saves the settings even if I remove the car battery.


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## warbital (Feb 5, 2013)

rocketsarefast said:


> You know, that might actually work. I feel a little dumb for not thinking of that. Two big diodes and a 470uF cap might solve everything. I might not even need the relay if the ignition wire of the head unit pulls very low current. This will be the first thing I try when I start installing the head unit. I even have those parts already. Thank you very much. Man I feel dumb.


That could work, I did something very similar on a cheap Head Unit to stop it from powering off during cranking. It all depends on how much current the HU is drawing and how long you take to start the ignition after closing the door.


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## diy.phil (May 23, 2011)

That arduino method sounds like a nice project!


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## cajunner (Apr 13, 2007)

if you're diy handy, maybe you could hack the app on the smartphone that finds your car for you, to also start up the boot when you get within 30 feet of the car...


that would be pretty cool, and since it is not perilous like code grabbing the starter or requiring some kind of ignition lock-out, it would be easy enough to do if one had the inclination.

sort of the Bill Gates/Steve Jobs house, where things happen as he enters and exits each room, the same could work in the car.


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## rocketsarefast (Apr 28, 2015)

cajunner said:


> if you're diy handy, maybe you could hack the app on the smartphone that finds your car for you, to also start up the boot when you get within 30 feet of the car...
> 
> 
> that would be pretty cool, and since it is not perilous like code grabbing the starter or requiring some kind of ignition lock-out, it would be easy enough to do if one had the inclination.
> ...



Yeah, that's kind of a solution to my "Option 3". Start booting the radio as I approach. I probably will not attempt this solution because it relies on the phone having the app running, and it is a significantly larger project. But, you are right, it would be awesome.

What will likely happen in the future, is car stereo manufacturers will get slower and slower boot times, and finally start implementing a sleep feature like tablets, and never actually power off. There are even some android based head units that already do this, but at the moment, they don't yet appeal to me. The sound quality is often much less (according to reviews, I have not heard any of them myself), and usually no volume knob, or any buttons. However, I am considering it.


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## rocketsarefast (Apr 28, 2015)

I thought of another solution that might work.

I could mount a motion sensor in the dash that is always on, but low enough power to not drain the battery. Then the motion of opening the door and sitting down could start the head unit. This might also require diodes and a capacitor, but would not require tapping into the dome light. I could even go nuts and point the motion sensor out the driver window to make it activate as I walk up to the car.

If I can find the dome light wire somewhere under the dash, I think I prefer that solution. The motion sensor might be too sensitive and activate the head unit when people walk by the car or trees casting shadows into the interior. Also, the dome light with 2 diodes and capacitor approach would guarantee not draining the battery.

Just wanted to mention this idea in this thread.


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## diy.phil (May 23, 2011)

umm... but hey ... come on... I still want to see an arduino project


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