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Picture of Android Tablet as Car PC
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An android tablet ia a logical choice for a car PC. The device offers additional features beyond regular car stereos. While many car stereos have GPS, the android device offers a more intelligent GPS. It has all of your google contacts addresses already in the GPS, it has your calendar with events and their locations, Chrome to phone can automatically send directions from your computer to your car. The device can store music, use internet radio, or play music using a cloud player such as Amazon cloud. These are features not available on even the most high end luxury cars.

I recommend choosing a tablet that already has a car dock. This dock can be easily modified to be permanently installed where a double din CD player would normally go. Also, with a car dock, the device will be easily removable so you can prevent theft and use the tablet elsewhere.

Tools:
Wire Strippers/Crimpers
Soldering Iron (Recommended)
Screw Drivers
Drill
Dremel with Cutting Blades

Equipment:
Tablet with Car Dock ( I chose Samsung Galaxy Tab 7+)
1/4" Sheet Lexan (Approx 10"x6")
Paint
1-1/4" Hole Saw
3/8" Drill Bit
Amplifier
Car Audio Adapter
Spade Plugs
Wire - Heavy Gauge to Power Amp
Wire - Medium Gauge for Speaker Signals
Grommets
Electrical Tape
Scotch Tape
 
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Step 1: The Audio

Picture of The Audio
Replacing the stock stereo unit with a android tablet requires an external amplifier for the sound to play through the speakers. I choose a 4 channel amplifier. Four channel because my car has four speakers. I have the amplifier mounted under my passengers side seat, but the amp could be mounted just about anywhere.  I chose just about the cheapest amp I could find.  I don't listen to much music, mostly audio books and podcasts, so I was not too concerned with sound quality.  I do listen to music using this amp and it sounds good enough for my ears.

Step 2: Wiring the Amplifier

Picture of Wiring the Amplifier
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The amplifier will be powered directly by the battery.  This will involve running heavy gauge wires from you car battery to the amplifier.  Read the instruction manual of the amplifier to determine the necessary wire gauge for powering the amplifier.  There are kits online that have pre-packaged wire for amplifiers or you can save yourself some money and go to the local hardware store and get them to cut a few feet of wire for you.

Step 3: Amplifier Location

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The amplifier is out of the way in the truck of a car, but it is also a long way away from the battery.  I chose to mount the amplifier underneath the passengers seat to limit my cable run lengths.  The seat had to be removed but this is actually quite easy.  Only four bolts hold the seat in along with the wires for the occupancy detector for the airbags which has to be unclipped.

Step 4: Amplifier Tools and Accessories

Picture of Amplifier Tools and Accessories
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You will need a crimper to crimp spade plugs onto the end of each wire.  I have some spade plugs that have heat shrink around them which I think is really cool and looks very professional.  You will also want loom to cover the wire inside the engine compartment.  High temperature loom is highly recommended.  The loom may be hard to find at local stores but is available at McMaster Carr.  You can tell the difference because high temperature loom will have a gray stripe on it.  This loom is specifically designed for high temperatures locations like that of an engine compartment.

Step 5: Amplifier Power Warning

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Also, you have to put a fuse in the power cable of the amplifier.  Radio shack sells small waterproof inline fuse holders that can be used for this.  Very Important: Remember to put a fuse into the power cable for the amp as close to the battery as possible.  Without this fuse, a short can set your car on fire.  Yes really.

Step 6: Running Wire Through Holes in Metal

Picture of Running Wire Through Holes in Metal
Also, to get the power from your battery to the amplifier you will probably have to drill a hole in your firewall of your car.  You may be able to poke the wire through a hole already there, but it is quite easy to drill a hole in the firewall.  Here or anywhere you run wire through a hole in metal use a rubber grommet.  This will prevent the jacket of the wire from being worn down from rubbing on the metal.  I have a small hole in the passengers side footwell.  The power cable for the amplifier runs through the hole, directly under the carpet, up through a hole in the carpet underneath the seat to the amplifier.

Step 7: Amplifier Sound - Vehicle Harness Adapter

Picture of Amplifier Sound - Vehicle Harness Adapter
For attaching the amplifier to the speakers, I recommend you buy the adapter for connecting an aftermarket stereo to you stock system. This will prevent you from needing to cut any of the wires in the car.  If you go to Crutchfield's website and look to buy an aftermarket stereo there will be two adapters.  One for you car and one for the stereo.  These adapters are labeled and have short stripped wires on each end.  Simply order the one that is for the car and attach it to the plug that was originally in the back of your stock stereo system.

Step 8: Amplifier to Car Adapter

Picture of Amplifier to Car Adapter
You will need to run 2 cables per channel and a signal cable from the amplifier to the car adapter.  This connection can be either butt-connected with crimp style connectors or (better) use soldered connections with heat-shrink.  I recommend a piece of scotch tape wrapped around a sheet of paper to label the ends of the wires.  The other option instead of scotch tape is clear heat shrink.  This really leaves a really nice looking label.

To connect the source, in this case the android tablet, a stereo mini to rca (red and white) is needed. If you plan on having the device charge while it is being used, a ground loop isolator will needed to be added to this audio circuit. If powering the device and also using it as an audio source without this isolator you will hear a lot of static.

Step 9: Charging the Tablet - Adding a Circuit

Picture of Charging the Tablet - Adding a Circuit
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Using the GPS in the tablet will eat the battery pretty quickly.  So it is nice to have the battery of the tablet charging as you drive down the road.  Probably the best way to do this is to create a separate fused circuit in your car.  If you look in the fuse box under the hood there will be some auxiliary fuse holders that are empty.  The labeling of the fuse box is usually on the bottom of the lid for the fuse box which will reference your car's manual.  To add you own circuit you can buy an add-a-fuse.  This is a device that has a fuse and a short power wire.  To this power wire you will want to add a female 12 VDC power socket (a cigarette lighter style socket).  These can be found in auto parts stores or online.  The red wire goes to power this socket and the other end must be ground.  I found plenty of room where the CD player used to be to install the power socket.

Step 10: Charging the Tablet

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Some of these auxiliary fuses draw current if the car is on or off and some only draw current when the vehicle is turned on.  The quickest way to tell which is which is just to plug the add-a-fuse in to different fuse spots with something connected.  Important - By connected I mean with a power socket and the unmodified car power adapter for your tablet.  Turn the car on and off and see what happens.  I chose a fuse that did not draw any current when the car is off as to not drain the battery.

Step 11: Taking Out the Old CD Player

Picture of Taking Out the Old CD Player
I first had to remove the portion of my dashboard that contained the stock CD player.  If you are unfamiliar with doing this for you particular car, I recommend a Haynes manual.  This manual will help you find every screw and clip holding that dash in place.  With the dash out, I measured and cut a piece of 1/4" lexan slightly larger than the hole where the stock radio was.  Lexan can be found in your local hardware store in the glass cutting section.  Just about anything can cut it although I still have problems getting a really clean edge.  Luckily in the application all of the edges will be behind the dash so it won't matter.  The dash is probably curved and you may notice small gaps in the side because the lexan is flat.  You can ignore these because when the tablet is in place, they won't be visible.

Step 12: Mounting the Lexan

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To keep the lexan in place, I attached it along the back using one of my favorite inventions.  A two part epoxy putty.  This stuff is great for attaching weirdly shaped items.  Just mix it together and stick it on.  When it dries it will be rock hard and solid.

Step 13: Installing the Mount

Picture of Installing the Mount
I used a 1.25" hole saw to drill a hole in the middle of this piece of lexan. After cutting off the suction cup portion of the mount for the tab, I epoxied it into the hole in the lexan. I also drilled a 3/8" hole next to the mount to run the power and audio cables through.

Step 14: Paint

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The lexan is fairly easy to paint.  I roughed up the surface with 220 grit sandpaper.  I then applied a layer of spray primer and then a layer of flat black.  The paint does not have to be perfect as the mount will cover most of the paint job.

Step 15: The Finished Product

Picture of The Finished Product
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The final product has a clean and professional looks but not quite stock. The only thing left is to upload some apps to enhance the experience. I recommend Google Navigation, Pandora, Amazon Cloud Player, tuneFM, Audible, doggCatcher, ChromeToPhone.

Remember to always drive safely and obey all traffic laws. This is not a device to watch movies or read emails when you are driving. It should be used in a safe and intelligent manner.

Step 16: Mistakes I Made for You to Learn From

Picture of Mistakes I Made for You to Learn From
I did not like the idea of having to plug the headphone cord into the top of the tablet.  I knew that the dock connector had pin outs for analog audio.  I bought a cable that allowed me to charge the tablet as well as to play audio through the same cord.  However when testing this in the car, I was unable to get rid of the noise when charging the dock and powering the amplifier at the same time.  There may be an electrical hobbyist on here who could tell me why or help figure out a solution, but I was unable to figure out a solution. 

After this didn't work I bought a bluetooth audio receiver that I plugged into the amplifier.  This device worked and I was able to use the audio without attaching a second cable.  However, I the sound isn't as clear as with an audio cable.  I also run it to issues where the bluetooth has trouble connecting.  For the time and effort, I would highly reccomend just using the headphone cable.  It is the best option I was able to come up with at this time.
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MarkA232 months ago

Hi GabrielK2,

I took apart a cigar lighter to USB adapter and mounted it into a spare switch blank (next to the rotary switch). Just need to replace the two connections and splice into the stereo feed. Works really well and I don't have lead hanging all the way down the centre console.

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GabrielK25 months ago

Instead of adding a cigarette lighter style power jack, would it be possible to just wire in a USB jack? Since the original radio is going away, could a USB jack be powered from the vehicle harness adapter the same way the original radio was?

no usb is 5volts where almost all the electronics are 12v what I would do when I was an installer is solder a wire to the nipple of the cigarette lighter plug and one to the outer ground spring and then T tap those to switched 12v behind the dash that way you still have your cigarette lighter socket and your tablet wont drain the battery

Kiteman3 years ago
This is a cool project, but readers ought to be aware that it is probably illegal in the UK, since it is not a dedicated satnav or music player.

You can get round it by wiring it in so that it cannot function whilst the engine is running.
magnuswf Kiteman6 months ago

Or maybe running a on/off/standby switch to the handbrake? Handbrake pulled=tablet. Handbrake loosened=no tablet for you.

Figures.
Great project - although there are plenty of bluetooth enabled after market systems available - which could make the audio linking aspect a bit easier.

Saw this regarding legaility in the UK...
http://www.in-carpc.co.uk/legislation.htm
"
Ensuring that the driver is not distracted

Section 109 of the Road Traffic Construction and Use Regulations clearly states what information can legally be displayed on a screen that is within the driver’s field of vision in a moving vehicle. All our fully installed systems apart from the Basic and Lite packages include the Centrafuse software interface, which provides a touchscreen friendly user interface. Centrafuse comprises many modules that perform different functions, examples of which are the navigation module, the hands-free phone module and the DVD player. When the vehicle starts moving, any modules that could cause distracting or illegal information to be displayed on the driver’s screen are automatically disabled. Using the examples above, the DVD module would be disabled but the navigation and hands-free modules would not, as these are both legitimate uses of a driver-visible display.

In addition, Centrafuse is automatically activated whenever the vehicle starts moving, so that it completely blocks the Windows desktop and any other running programs, and can only be minimised again when the vehicle is stationary.

For fully installed systems that do not include Centrafuse we can use other means to ensure that the system remains completely legal.

"

So it looks like centrafuse could be your friend here ... see http://www.centrafuse.com ... and they have a bunch of apps already available to look at car diagnostics etc

This is the law
"
109.—(1) No person shall drive, or cause or permit to be driven, a motor vehicle on a road, if the driver is in such a position as to be able to see, whether directly or by reflection, a television receiving apparatus or other cinematographic apparatus used to display anything other than information—

(a)
about the state of the vehicle or its equipment;

(b)
about the location of the vehicle and the road on which it is located;

(c)
to assist the driver to see the road adjacent to the vehicle; or

(d)
to assist the driver to reach his destination.

(2) In this regulation “television receiving apparatus” means any cathode ray tube carried on a vehicle and on which there can be displayed an image derived from a television broadcast, a recording or a camera or computer.
"

Which means that you could not use it to change your music selection while driving ... but you can use it for a sat nav and to show images from a rear view camera
Now if only there where an app that let you use an Android tablet as a speaker phone unit for a Bluetooth enabled cell phone.

Would be imaginable :)

assman662 years ago
Nice write up. Working on my own because i came across this one. One question, how are you using the 4 channels out if the amp has 4 channel inputs? from the looks of it you have 2 channels going in(the 2 rca) to 4 channels out(4 speakers). I have installed amps before but am i missing something here, don't you need 4 channels in to get the 4 channels out?

thanks in advance
magnuswf assman666 months ago

I'm pretty sure that a 3,5mm jack can transmit sorroundsound, which goes from the signal. L+R into 4 channels, front left, front right, rear left, rear right. Maybe that was the answer to your question?

BigMaxee3 years ago
Hi Guys, I am very new to this forum and find all this discussion very interesting. I have a 7" Android device which has outlived its usefullness to my children apparently and so I thought it might be fun to rig it up in the car for playing tunes and using as a gps and reversing camera. I noticed that JFarmer had quoted some regulations including the following "(2)In this regulation “television receiving apparatus” means any cathode ray tube carried on a vehicle and on which there can be displayed an image derived from a television broadcast, a recording or a camera or computer." Now correct me if I'm wrong but I am pretty certain none of the devices any of us have or are talking about has a "cathode ray tube". Does this mean that the laws quoted by Mr JFarmer are nul and void perhaps?
Just a thought... many have gotten by on a technicality before. :)
magnuswf BigMaxee6 months ago

Adding to LunaEros' comment, in some cars, with in-car intertainment, fx a DVD player, you have to pull the handbrake, to "prove", that you are standing still.

LunaEros BigMaxee8 months ago

That is basically null and void.

What most laws state these days is that video entertainment cannot be in the view of the driver while the car is running.

Video for rear view and backing up is ok though.

ShaQ1nJ8 months ago
Very informative article!! You answered so many random questions I've had over the years, like why does charging cause static to appear in the audio? Or how can I stop charging a device once the car is off? Thank you so much for writing such an excellent guide.
Where did you find the bracket for the tablet?
I started mine with a Samsung Galaxy tab 3 7". I'm doing a removable mount. And since everyone is having an issue with the whining noise, I found that using the Bluetooth function for the stereo, it doesn't create the noise. And I'll be using the ELM OBDII bluetooth adapter so I can monitor my vehicle using a split-screen app.
jbianchi31 year ago
Could you use a otg plug and dac instead of the 3.5mm and power cable?
koney1 year ago

How do you solve automatic powering ON/Off with ignition?

1st thing is setting the "Stay awake while power is connected" setting under developer options, and setting the screen timeout to a short value under display settings; if you connect the charging cable to a power source that goes on and off with the ignition, but what If the standby time of your tablet is not enough to handle your typical time with the ignition off? You may use an app like Tasker to set additional rules, like turning Wifi or cell connection off when the car's power is off. But how to solve complete On/Off ?- Something like hibernation like in Windows would be really cool - could be quite fast (tablet has a small ram) .

pm116 koney1 year ago

Hi there, i recently found a free app that as soon as you unplug the charger it automatically pause all media and navigation apps that drain the battery pf my android tablet. Its called AutoSleeper and this is the URL for Google Play.

https://play.google.com/store/apps/details?id=com....

Check out its features:

It is the best solution i've found.

  • Your Tablet goes automatically to Stand By mode when you turn off the car engine- The Song you were listening to Pauses - When you turn on the engine the Tablet goes On again without pressing the Power Button:- Your GPS is on again- Your music continues exactly where you had left it- You decide if you want your Tablet to go to Stand By mode or to Off mode - You decide within how many seconds after you turn off your engine you want your Tablet to deactivate.- Autosleeper is designed for Tablets and Smartphones

If you have any other suggestion let me know.

FranzIonut2 years ago
Some apps for my tablet while I'm using in car and o few other advices related to what i've read :
http://gizpoint.com/how-to-tablet-as-car-pc-using-tablet-for-navigationmusicvideointernet-in-car/
If you don't have a dock,you can go further and make a custom install in your dash.
JozielHi2 years ago
Can you show a link to where you got the Car Dock? I'm only finding them for the Galaxy Tab 2 7.7 (Verizon version). I need it for the regular Galaxy Tab 2 7.0. Great job btw.
Sassah1222 years ago
This is good for people who have a lot of time and money on their hands. I did a very simple thing.
1. Get iPhone of android windscreen mount.

2. Use a standard audio cable to transfer audio signals from phone to car. I used aux port but you could also use a special cassette tape that provides a 3.5 mm jack.

3. Connect the phone's usb car charger to my 12 volt output.

4. Download apps and enjoy!
primo72 years ago
Great idea but has one flaw. There is no android software. In my car I have carpc with software Centrafuse. Centrafuse have handsfree phone option when I make the call or recive the call the music mute
and when I use integrate navigation (Garmin) that when spoken instructions the music mute. It would be great if it would be possible in Android phones and tablets.
hamsammy2 years ago
Great write up! I'm running into the same issue with a build of mine for an ipod cable which goes from dock 30 pin to USB for charging and 1/8" for audio. The audio sounds great until I plug the power portion in and then, NOISE! I haven't been able to figure it out but suspect it's just poor quality shielding within the cable since it's getting clean power from a computer PSU. Did you ever figure yours out?
willyam111 (author)  hamsammy2 years ago
I would try adding a ground loop isolator into the circuit.
lkatrencik2 years ago
if you don't have enought room for dock connector you can make your own http://forum.xda-developers.com/showpost.php?p=20710266&postcount=14

(samsung)
amarshall92 years ago
I never thought about using a tablet for a radio. I rather listen to my android tablet then listen to the radio because the radio plays garbage repeatably.   Does it work wireless like some obd II systems.
orbit12123 years ago
Hey you should definitely make a series of videos on this this is amazing and i will be doing it in my car.../// i want to also integrate some engine stuff such as speed, rpms, if the tablet can read it i want to see if it can google maps integration as well just some ideas
willyam111 (author)  orbit12123 years ago
The Tekzilla recently did a show segment on a cheap bluetooth obdii reader that can transmit to a tablet running Torque to give you those engine parameters. Here is the bluetooth module. I personally have never used it so I can't speak to how well it works but they seemed to like it.

http://www.amazon.com/Soliport-Bluetooth-OBDII-Diagnostic-Scanner/dp/B004KL0I9I/ref=pd_sxp_grid_pt_0_0
lordvellos3 years ago
Just out of curiosity, but since android is an "open" platform, are there in the market apps or hack that it could trully be converted to the central of the car, attaching it to different sensors to get temperatures, rpm and all other kind of stuff?
Yes you can, and it is a shame that the author did not delve into a vehicle data interface (OBD II). The android market has a host of apps that read in important vehicle data from an OBD-II interface.

You see, all cars from 1996 and later have a standard port underneath the driver's dash that allows for auto shops to run diagnostics on cars and to even set some variables. One of these variables is the state of the "engine light", which is how shops tun it off when their work is complete. Other information available ranges from fuel consumption to o2 sensor readings, practically all of the data that the car's computer has on hand, including those that you mentioned. Sadly, one of thee ones commonly missing is oil pressure.

Anyways, this port can be connected to by an aftermarket reader that uses a decoding chip (one of the most popular is called "ELM 327"). This reader may be connected to your android, ios, or other device, granted that it has the software to read the incoming data. There are many bits of software out there for reading OBD data, my favorite is "Torque" on the android market.

As for connectivity, you could use tethered or wireless. Wireless would be in the form of a wifi hotspot connection or a bluetooth connection. I curently use a wifi OBD-II adapter in my own car with the Torque application. This adapter only cost $25 on Amazon and seems to work perfectly for me (though there seem to be many cheap brand versions that do not work well). I believe that Android supports all communication formats, while iOS devices do not support the data transfer channels in a bluetooth connection.

There's a lot of info that I have not put in here, but I hope this answers your questions. On a side note, my car did not come with an mpg calculator, but Torque works wonderfully at calculating instantaneous, average, and trip mpg.
Fichtenelch3 years ago
And don't forget to install a fuse within the first 30cm of wire from the battery! This is very important to protect the wire and the car.
bdore3 years ago
You could add the 12v power socket with an inline fuse to the remote (power antenna) wire from the wiring harness you bought. That would make things simpler and would not require cutting any stock wires.
Didn't know about this ground loop isolator... now i know why i get a lot of static on my rig. Thanks pal.
Static or alternator whine? Usually in cars it's a whine that changes pitch with the speed of the engine.
Definitively whine (mistook the sound for plain static)... its pitch gets louder as i accelerate, so i guess it's because of the alternator spinning more rapidly...
Check your grounds, and check for a fried channel on your amp, happened to my first amp thanks to me dropping it to like 1ohm before I even knew what ohms were, lol.
WolfTohsaka3 years ago
Great instructable !

Just one thingie... when replacing the car stereo, you use a harness to connect to the speakers... why not use a harness to get the (fused) stereo's 12v to power the amp and tablet ?

Kevin
willyam111 (author)  WolfTohsaka3 years ago
jdonor got it right. The amp draws a lot of current and you need very thick gauge wire to power it. Connecting to the battery is the best way to do this. Don't forget the inline fuse holder when powering the amp. And be sure to read the instruction manual that came with you amplifier or get it professionally installed if this part scares you.
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