Author Topic: usb/gps power question  (Read 3483 times)

Lucky

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usb/gps power question
« on: August 01, 2007, 01:38:09 PM »
you guys have been talking about GPS's lately, & for a while i've wanted to use mu Streetpilot c320 on my bike.

the problem: the gps is powered by the mount to a 12v cigarett lighter adapter.  there is no way this adapter will fit in my fairing, but without the mount & a bit of industrial velcro, it'll fit very nicely.

my question:
i've noticed that when i plug the gps into the usb port on the computer, it powers on.

is there any reason i couldn't just connect a lighter plug to a usb cable? i figure i'd have to step it down to 5v (isn't usb 5v?) & match the (mili) amperage. (i'm clueless on how to do this, but i know how to solder resistors to a board)

DaveTn suggested i could probably just use a cell phone adapter, but my big concern is burning out a gps i can't afford to replace, & the wife uses it alot.

thanks guys!
--Lucky
« Last Edit: August 01, 2007, 01:57:40 PM by Lucky »
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Lucky

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Re: usb/gps power question
« Reply #1 on: August 01, 2007, 02:06:40 PM »
here are some specs i've found on the web, if it helps:

c320 power specs:
http://www8.garmin.com/products/sp320/spec.html

usb specs:
http://pinouts.ru/Slots/USB_pinout.shtml

so if the gps runs on 12v, & usb is 5v, then i'm going to guess that a usb powered device that has a 12v plug is 'stepped down'.  meaning that the gps actually runs on 5v...

correct?
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Tanno

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Re: usb/gps power question
« Reply #2 on: August 02, 2007, 10:10:58 AM »
Plug in the cigarette lighter power cord in any 12vdc socket. Now, with a voltmeter, check the voltage and all the pins and possible pin combinations to see if it's supplying 12v or 5v. Then and likely only then will you have your answer. At least that's what I'd do.

Likely it's 5v and a max 500 mA draw.
« Last Edit: August 02, 2007, 10:14:41 AM by Tanno »
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Walt_M.

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Re: usb/gps power question
« Reply #3 on: August 02, 2007, 05:17:09 PM »
That may not work if the voltage is controlled by resistors only. You need the rated current flowing in the circuit for the voltage to drop across the resistor. If it is a true regulated voltage using a Zener diode, that should not be a problem.
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Lucky

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Re: usb/gps power question
« Reply #4 on: August 02, 2007, 07:26:29 PM »
Walt, can you say that in laymans terms? if i can go to radio shack & get the parts, i could build it.  or do i just need to be able to test the plug?

i thought that if usb output is universal (from the pc) then wouldn't usb output from a 12v car pigtail be the same?
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Coil Coyle

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Re: usb/gps power question
« Reply #5 on: August 03, 2007, 04:14:26 AM »
Lucky,
            You just need to supply the 5 VDC with a power supply that makes more current than you need. Ohm's law will control the device current.

http://www.shindengen.com/resources/Content/3/8/documents/10whu.pdf is an example of a DC/DC converter. It's $45.00 from Mouser.com but a search of your favorite Electronics supply for the cheapest DC/DC rated 10-18 in/+5 out and more watts than you need is all your GPS USB pin will need.

          Use the pinout that you have for the USB; pin 1 gets the +5, pin 4 gets the -5. I think the power wire should be shielded with a grounded foil cable and the 5 vdc power circuit should "float" without an actual connection to the bike ground or, if you want to reference it to the bike negative ground, jump the -5 to the -12 at the chip mount only. The point of that is that you don't want ground currents of the bike affecting the 2 communication wire signals if you use them.

$0.02
 ;)
Coil

PS. Here's 500mA @ 5VDC cheap!
http://www.newark.com/jsp/Semiconductors+&+Prototyping/Power+Management+ICs/NATIONAL+SEMICONDUCTOR/LM2594HVM-5.0/NOPB/displayProduct.jsp?sku=41K3810
But you have to build the circuit, nice Data Sheet tells (on top of page 8 and the circuit board is on page26) how.
http://cache.national.com/ds/LM/LM2594.pdf
« Last Edit: August 06, 2007, 03:39:12 AM by coilXZcoyle »

Lucky

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Re: usb/gps power question
« Reply #6 on: October 10, 2007, 02:47:03 PM »
I found a car adapter to USB in my local Crappymart for 9 bucks.  i bought it & went to their website before i opened the package, no specs given, so i just held my breath & plugged it in..

WORKS! cool, another distraction!
--Lucky
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ironb12s

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Re: usb/gps power question
« Reply #7 on: October 10, 2007, 08:21:25 PM »
KISS, man.  You've got plenty of room in your dash for an auto plug.  I've got an an auto plug on the right side for GPA and Escort, BMW plug on the left for Gerbing electrics.  This is on my GSF1200S, and it's got a "dash" about 1/4 the size of the plate behind the speedo cluster of the Vision.  If'n you wants pics, I'll get them tomorrow - dark here at present.

Both of my plugs hang off of the taillight circuit, fused in the block.  Also have the turn signals wired as running lights on the same.  Of course, the Bandit isn't known to have the same problems with it's generator...it's mounted on top of the case behind the cylinders.
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YellowJacket!

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Re: usb/gps power question
« Reply #8 on: October 10, 2007, 08:31:10 PM »
Suuuuhhhhhwheeeeeeeett!   ;D

Oh, yeah, I'm back from B'mgham.  I thought about you while I was on my way home this afternoon.  85 to 95mph and smooth sailing the whole way and hit a 6 mile traffic jam in Loudon at the bridge on 75. 1.5 hrs from there and I was finally home.  1/3 of the trip back for 6 miles.  ugh.  Woulda stopped by but the Loudon exit was way backed up too.

David


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Lucky

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Re: usb/gps power question
« Reply #9 on: October 10, 2007, 09:44:01 PM »
KISS, man.  You've got plenty of room in your dash for an auto plug.  I've got an an auto plug on the right side for GPA and Escort, BMW plug on the left for Gerbing electrics.  This is on my GSF1200S, and it's got a "dash" about 1/4 the size of the plate behind the speedo cluster of the Vision.  If'n you wants pics, I'll get them tomorrow - dark here at present.

Both of my plugs hang off of the taillight circuit, fused in the block.  Also have the turn signals wired as running lights on the same.  Of course, the Bandit isn't known to have the same problems with it's generator...it's mounted on top of the case behind the cylinders.

look closer at the pic, to the right of the voltmeter & above the fan monitor light.  this way my wife can still use the windshield mount in the car.
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h2olawyer

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Re: usb/gps power question
« Reply #10 on: October 10, 2007, 10:42:28 PM »
Cool, man - "Where do you want to go today?"   ;D

H2O
If you have an accident on a motorcycle, it's always your fault. Tough call, but it has to be that way. You're in the right, and dead -on a bike. The principle is not to have any accident. If you're involved in an an accident, it's because you did not anticipate. Then, by default, you failed.

ironb12s

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Re: usb/gps power question
« Reply #11 on: October 11, 2007, 12:21:55 AM »
I looked at your pic, and it appears that you have a lighter socket on the lower left below both of your gauges, I can't tell what they are.  BTW, the one 1983 XZ550RK on Ebay has 3 gauges mounted on top above the speedo cluster.  I'd consider getting a BMW plug, and installing it on the other side of the "dash".  The BMW plug isn't as big, and has better contacts than a typical auto plug.  I have a Radio Shack plug with an LED to indicate power when it has it, and the circuit that they're on is hot only with the key in run or park, tied directly to the tail.  Only blown the fuse once, when a bit of water got into a connection...

Also, check the manual of your C320, I don't recall them as being waterproof...only for use inside closed vehicles.  But, behind your fairing/windshield, it may be fine.  I have my components on the right side of the handlebar, with RAM-MOUNT.  I have a Chartplotter 176 which is a marine GPS, made for being on the water...
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Lucky

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Re: usb/gps power question
« Reply #12 on: October 11, 2007, 07:58:50 AM »
Your kidding right?  :D
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ironb12s

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Re: usb/gps power question
« Reply #13 on: October 11, 2007, 11:12:46 AM »
Here is my setup:



Kidding about what?   ???

You'll have a hard time finding a weatherized USB socket, but you may find an adapter.  Unless, you already have...    :)

The down side of my installation is if the fuse for this circuit blows, I lose the gauges and running lights.   ;D  Fortunately, I carry spares in case of such an emergency...
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h2olawyer

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Re: usb/gps power question
« Reply #14 on: October 11, 2007, 02:13:05 PM »
That's why I decided to make my own wiring harness for the additional circuits & hooked it directly to the battery.  Didn't want them influencing the under-engineered factory wiring.  The trigger wire for the relay doesn't require much power at all.  Plus, each accessory has its own fuse.

H2O
If you have an accident on a motorcycle, it's always your fault. Tough call, but it has to be that way. You're in the right, and dead -on a bike. The principle is not to have any accident. If you're involved in an an accident, it's because you did not anticipate. Then, by default, you failed.

ironb12s

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Re: usb/gps power question
« Reply #15 on: October 11, 2007, 09:19:32 PM »
Got this from the LDRIDERS forum:

http://www.amazon.com/Zip-Linq-12V-Auto-Adapter-ZIPPWR-DC/dp/B000167V50

Sometimes it's nice to be some broadly connected...    8)
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KayLee: "'Ah-uh, she'll fool ya."