comp in car question

[minoukat]

if I wanted to install a computer in my car (if I had one :D), to listen to movies and MP3s, could I just connect it to the car's amp and sound system ?

[FunkDaMonkMan]

if the car's headunit had RCA "in" jacks in the back, then you would be able to hook that up directly to your sound card, (with adaptors on the cable), to play your sound in the car. I have thought about doing this also, but the problem for me is summer heat. I guess that in canada you wouldn't have to worry about it as much.

[minoukat]

Originally posted by FunkDaMonkMan
if the car's headunit had RCA "in" jacks in the back, then you would be able to hook that up directly to your sound card, (with adaptors on the cable), to play your sound in the car. I have thought about doing this also, but the problem for me is summer heat. I guess that in canada you wouldn't have to worry about it as much.

How do I know if it does have RCA connectors ? Do I have to remove the radio to do it ? (car is Passat 91 btw, if that helps ...)

[FunkDaMonkMan]

if you don't have the manual for it, then yes you have to remove the headunit. Unless, you can see the rear of the unit from under the dash. My guess is if its an older model STOCK head unit... then it probably doesn't.

[Mark620]

Generally Only custom radios/CD/MP3 players have RCA connectors- Stock equipment probably does not have them.

[four4875]

i've seen few aftermarket high quality ones with ins... so i really doubt it will have ins on a stock.

[cryogen97]

you can buy an FM modulator. Just get one that plugs directly into the antenna.

[penquissciguy]

Originally posted by minoukat
if I wanted to install a computer in my car (if I had one :D), to listen to movies and MP3s, could I just connect it to the car's amp and sound system ?

You would also of course have to worry about controlling your playlists, movie player, etc. If you're talking a laptop on the passenger seat, no big deal. Otherwise, you need to do some planning as to how to interface with your pc.

To power your beast, I would suggest a AC inverter that you could plug directly into your car's DC supply. That way, you don't have to modify any PC equipment or build a custom supply - just plug and play. (hey, that sounds catchy... :D )

Ken

[bubba gump]

Originally posted by penquissciguy

To power your beast, I would suggest a AC inverter that you could plug directly into your car's DC supply. That way, you don't have to modify any PC equipment or build a custom supply - just plug and play. (hey, that sounds catchy... :D )


Im aware that as the engine moves at a substantial rate, it sort of recharges the battery for the car...right? Even if he had a branch off of the car's DC wouldnt it still be sapping the car's battery? Id think that the car wouldnt be able to power the computer for too long, but hey i dont know how much electrical power is output by a car :D

Im just afraid that when he gets this all said and done hes out in hte middle of no-where crankin his tunes and his battery runs out :rolleyes:

[JoT]

the engine rotates the alternator(sp) which in turn recharges the battery (at all times, I think)

[Turando]

yeh the alternator on the flywheel does re charge the battery, but you are better of using a standalone 12v high amperage battery, as you will totally drain the car batt, depending on what coil you are using with your plugs. your best bet is to use a risc arm processor setup, alot less power usage, and heat, and it will be able to stream mp3's.

Cheers, Turando

[LuckyBob]

Whoa there... before this thread gets out of control with misguided information, let's discuss this in detail with some figgures to back it up.

A little info about car electrical systems:
The battery exists pretty much to start the car and that's it. Once the car's up and running, the alternator (which is generally connected to the water pump with a pulley) provides all the power to keep the car going, and any excess power generated by the alternator is used to charge the battery back up to full.

Don't bother searching down information on the flywheel, since it's near the transmission and doesn't do anything for the charging of the car. Also, the coil isn't to be concerned with; it generates the pulses that spark the spark plugs. Coils don't draw enough sustained power to be horribly concerned with; they're a simple step-up transformer. They do produce a LOT of voltage (usually >50kV), but at a very small amperage (usually >1/100 an amp). Most of the time the total power sucked by the ignition coil on the +12VDC side is less than 5A.

We'll use my car as a reference vehicle. A 1984 Volvo 240GL, which I do all the work on.

If one were to go with the AC inverter route:
A 300W AC inverter sucks a maximum of 11 amps (that's only if the device requests that much power in the first place). 300w should be more than suffecient to run a car PC. My 1984 Volvo has a 75 amp alternator. As has been proven in the past computer VERY rarely suck as much power as the supplies are rated for, so we're at absolutely most using <1/7 of what the alternator in my car is capable of. I'm willing to bet that the majority of the time we'd be using something like 1/12 or 1/15 of the alternator's capacity. Hell, the windshield wipers suck the equivilant power of 430w AC inverter all the time.

Here's what you have to do: find out how many amps your car's alternator can put out, and make sure the computer you build doesn't suck a large portion of that. If it does, chances are with a bunch of other electrical parts running full bore, the alternator might be overloaded and it will slowly drain the battery. I'm willing to bet that none of our cars will have an issue powering a computer for playing MP3s.

An aditional battery will do nothing for you:
Yes, throwing an aditional battery in your car would provide you with more battery storage capacity, but if your alternator can't provide enough power to run the car and the computer at the same time, power will slowly leech from the batter(ies) to keep the electrical sysytem all happy. (By the way, lead cell batteries will fail quite quickly if they're run down to a low charge. They need to be kept close to fully charged at all times) Essentially, given a weak alternator, the longer you run the comp PC, the quicker you'll kill your battery. A second battery will just prolong the death. If the alternator's up to the task, a second battery will just be a waste of a hundred dollars, unless you intend to listen to music with your car off all the time.

My two bits on AC inverters:
We sell them where I work, and I've seen enough complaints about 'em to feel it necessary to mention this: they screw up the power system of the car. DC to AC inverters work by taking a steady +12VDC line, and recreating a line that's ten times the voltage, but is cycling back and forth between positive and negative sixty times a second. Suffice to say, the circuitry to do this tends to wreak havoc all the stuff upstream. If you've got an old car (as in pre-ECU engines) with no computer on board, you might do OK. Headlights and whatnot don't exactly need steady power going into to 'em. Conversely, if the computer in your car is sensitive to the amount/quality of power going into it, you might cause some long term problems.

If I had my way, I'd use DC-DC power supplies all the time - quite clean input and output in comparison; they're also smaller.

[minoukat]

thanks all for the electrical instructions ! :) Now, (back to the sound question) how could I connect the computer's audio card Line Out jack to the car's sound system, if I don't have an RCA jack on the head unit ? Could I just unsolder the cables connecting the cassette player, and solder the cable coming from the Line Out jack on the comp to it ? So if I wanted to listen to it, I'd just have to put in a dummy tape, the unit switches to reading the tape, which would now be connected to the computer, and thus spitting out MP3s and movies ? :)

[penquissciguy]

Originally posted by minoukat
thanks all for the electrical instructions ! :) Now, (back to the sound question) how could I connect the computer's audio card Line Out jack to the car's sound system, if I don't have an RCA jack on the head unit ? Could I just unsolder the cables connecting the cassette player, and solder the cable coming from the Line Out jack on the comp to it ? So if I wanted to listen to it, I'd just have to put in a dummy tape, the unit switches to reading the tape, which would now be connected to the computer, and thus spitting out MP3s and movies ? :)

I doubt the two signals (the one from the tape and the one from the computer) would be at the same level, which would mean either your computer would sound really quiet or would be so loud it would distort. Something like the FM modulator mentioned above would be more likely to work and would require a lot less effort.

As an aside, what software are you planning to run on this thing? What kind of hardware are you planning on using?

Ken

[LuckyBob]

Actually a tape adapter works just fine from when I've tried it. I also use my iPaq on a tape adapter all the time and the output level is pretty close to a sound card.

[bubba gump]

Wow, thats a lot of reading! Sorry to may have slightly led some misknowledgement, but as you can tell from my post, im not to knowledgeable in car electricals :(

Thanks for the info on that subject, ill try to remember that next time I need it!

'Bump

[CrystalMethod]

Originally posted by minoukat
thanks all for the electrical instructions ! :) Now, (back to the sound question) how could I connect the computer's audio card Line Out jack to the car's sound system, if I don't have an RCA jack on the head unit ? Could I just unsolder the cables connecting the cassette player, and solder the cable coming from the Line Out jack on the comp to it ? So if I wanted to listen to it, I'd just have to put in a dummy tape, the unit switches to reading the tape, which would now be connected to the computer, and thus spitting out MP3s and movies ? :)

Ok, first off, is it a stock head unit or something you bought?
Second, is there an option to add a cd changer on it?

[penquissciguy]

Originally posted by LuckyBob

My two bits on AC inverters:
We sell them where I work, and I've seen enough complaints about 'em to feel it necessary to mention this: they screw up the power system of the car. DC to AC inverters work by taking a steady +12VDC line, and recreating a line that's ten times the voltage, but is cycling back and forth between positive and negative sixty times a second. Suffice to say, the circuitry to do this tends to wreak havoc all the stuff upstream. If you've got an old car (as in pre-ECU engines) with no computer on board, you might do OK. Headlights and whatnot don't exactly need steady power going into to 'em. Conversely, if the computer in your car is sensitive to the amount/quality of power going into it, you might cause some long term problems.

If I had my way, I'd use DC-DC power supplies all the time - quite clean input and output in comparison; they're also smaller.

They are also more expensive and harder to find for PC applications. A question - would a power capacitor from a car audio application across the inputs for the inverter filter out the noise going back into the system? Seems like it would. Thoughts?

Ken

[spoken81]

You can't just plug your computer into the RCA jacks on any stereo. The RCA's are for output NOT input!! If you have a deck with CD changer control now thats a different story. The tape idea, like the ones to hook you discman up to your stereo, sugested above would work fine, just some rigging involved.


Now as far as power goes I don't see why you couldn't just run it off of the cold fusion generator...:bang head

[Stedeman]

NO use the Warp Core I am sure the Dilithian crystals can handle it!
[Thinks back]”Darn it Jim I'm giving it all she’s got”[/Thinks back]

A solution could be to add a “Y” splitter to your AMP (you will also need a 1/8th" input to RCA to make this work) inputs (use the headphone setting set to low on your sound card so not to over power the pre AMP and you will of course need to turn off your radio) and run the computer off a car power inverter (it connects to you cigarette lighter socket and changes the 12V DC too 120V AC) looks like a cheap car amp. As for your interface on the computer look to “www.myHTPC.net” its made to do this type of stuff and use a gyro (free air) mouse for controlling it.
Thank “james.miller” for the link to myHTPC

[LuckyBob]

Originally posted by penquissciguy

A question - would a power capacitor from a car audio application across the inputs for the inverter filter out the noise going back into the system? Seems like it would. Thoughts?

Ken

/me is just speculating here...
I think it'd help with the big spikes in power draw from the inverter (like when the comp first powers on and the power supply charges it's storage caps), but I think a lot of the smaller noise going upstream would require more than just big caps. I'd suspect one big cap, a few smaller caps, one or two REALLY (in the pF range) caps, and a fairly robust inductor would minimize the lot of it, but since I don't have an ocilliscope :mad: to look at exactly what a computer power supply does to AC or an inverter to look at the resulting effect on the DC power, I couldn't say exactly what components'd be necessary.

If I've got some free time before work tomorrow I'll see if I can crack open one of my spare ATX power supplies and see if it's feasable to use the inards of one of them as a DC-DC power inverter.

/me crosses his fingers for them using a 12-14v secondary winding, as it'll be dirt simple that way.

BTW I didn't mean to sound as negative as I did in my last post. I reread it and realized I wrote all that out in the haste to make sure the thread wasn't abandoned on the basis of semi-incorrect information. My bad.