O'Reilly logo

Car PC Hacks by Damien Stolarz

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Hack #51. Install USB Ports in Your Car

Installing USB ports in the front-seat area will give you the ability to easily add peripherals to your in-car PC.

Have you ever thought it would be nice if your car came with USB ports right on the dashboard? If this sort of geek chic is important to you, there are a variety of USB hubs that can fit the bill. The trick is to find a hub with a 2 x 2 stack of ports that is rectangular and has a narrow edge. (Your local computer store probably has dozens of USB hubs to choose from.) This will give a fabricator/installer a good unit to work with when they try to cleanly integrate it with your factory dash.

But there's no reason you must have the USB ports visible. Many vehicles have a center armrest designed to hide away CDs or other media, and this is a great place to put your USB hub. The glove compartment is another candidate, although it's a little harder for the driver to reach.

There are a couple of considerations when installing a USB hub. The primary one is power. Even with the upgraded USB 2.0 specification, every USB 2.0 self-powered hub has a 500-m A limit for each port. When the hub is bus-powered (i.e., only gets its power from the computer) that limit is lower, around 100 mA.

So, if you are going to connect a bunch of bus-powered devices, such as USB flash drives, Bluetooth adapters, flash drive readers, keyboards, and mice, you probably want to make sure that the USB hub you're installing is self-powered. Also, be sure to get a hub without an integrated USB cable. You may need to run the cable a fair distance from your computer, and integrated cables seldom have the length necessary for this.

Since USB hubs almost uniformly expect a 5V input, you're going to have to get a 12V-to-5V adapter in order to power it. At Radio Shack and elsewhere you should be able to find a cigarette lighter adapter with a variable output, like the one shown earlier in Figure 4-17. You need to run or tap into existing 12V switched or unswitched wires in the glove compartment or center armrest area, and connect these to the 12V-to-5V adapter [Hack #50] . Your best bet is to run what you need from the battery area [Hack #3] .


You should probably use a switched 12V wire when powering a USB hub to make sure attached USB devices are off when your car is off. You should use unswitched wires only if you have devices that recharge off the USB port, or if for some reason you do not want the devices to lose power.

You're also going to need to run the USB cable from wherever your car computer is to wherever you're putting the hub. You'll want to lift the carpet and run the USB cable underneath so it's out of sight. You can get a 15–25' USB 2.0 cable almost anywhere computer cables are sold. I've noticed no difference in quality between the $40 gold-plated super USB 2.0 cables and the $8 store special versions.

If you're running the USB cable to the console between the front seats, your car's service manual should give you hints as to how to remove and get under the console. Depending on the vehicle, you may be able to just run the cable under the carpet and beneath the passenger seat, and then snake it into the center console from below. (Chapter 1 has more information about running wires in your car.) If you're installing the hub in the glove compartment, you can run the wires all the way to the front passenger foot area and then run it to the glove compartment through the dashboard (Figure 4-19).

A USB hub in the glove compartment

Figure 4-19. A USB hub in the glove compartment

If you know ahead of time that you are going to be using a particular higher-power device, such as an iPod or portable hard drive, it would be best to run a wire for that device now. If your hard drive takes both FireWire and USB, you're in luck—with the right wire, the FireWire portion can usually be powered straight off of the 12V.

If your drive doesn't take FireWire, that's fine too—you'll just need a second 12V-to-5V adapter to connect the drive to. However, if your USB hub's 5V barrel connector is the same as your hard drive's barrel connector, you may have a simpler option—just unplug the USB extension cable from the hub and plug it into your drive. If your USB 2.0 hard drive is designed to work on bus power (some can and some can't), there may be enough power on the bus if you disconnect the hub. If this works, you can just leave the hub there until it is needed for other devices.

Having a hub in the front is valuable in many ways. You can use it to connect keyboards and mice [Hack #55] , GPS receivers, wireless remote controls [Hack #56] , or Bluetooth adapters [Hack #63] , just to name a few.

See Also

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required