## Re: Nuvi side plug

Expand Messages
• Glad you did the math on this - I was wondering about the voltage drop on this since the red wire in the cable did seem pretty thin! Larry WT9M
Message 1 of 13 , Apr 3, 2009
• 0 Attachment
Glad you did the math on this - I was wondering about the voltage drop on this since the red wire in the cable did seem pretty thin!
Larry WT9M

--- In tracker2@yahoogroups.com, "k7ybz" <k7ybz@...> wrote:
>
> Hi boys and girls,
>
> There is one problem that no one has addressed when using the FMI cable to power the Nuvi and that is the cable power and ground wires are 28AWG wire. The cable itself is 10.5 ft long which means the total wire length for voltage drop is 21 ft. The minimum voltage for a high power USB device is 4.75V. With a 5V regulator the maximum voltage drop is 0.25V. (Yes, USB devices may operate at less than 4.75V but is not guaranteed.) Back to the math. The maximum current you can put through the total cable length and still be within limits is 200 ma.
>
> The cable has four wires with a foil shield and drain braid. The white and green wires are actually 26 AWG wire and the red, black, and yellow are 28 AWG.
>
> Here are some options available and still use the same cable:
> 1. If you have a separate regulator that is adjustable, set it 5.25V. That is the maximum voltage that can be supplied to a USB device and with no current draw, the maximum voltage will not be exceeded.
> 2. Wire the green wire in parallel with the black wire.
> 3. Rewire the cable so that the green and white wires supply power and the signal wires use the red and yellow. Put the black wire in parallel with the ground wire you select between the green and white.
> 4. Shorten the cable.
> 5. Use options 1 and 2.
> 6. Use otpions 3 and 4.
> 7. Use options 1, 3, and 4.
>
> Since I have not disected the cable at the bump, I don't know if the shield is grounded at the bump. However, I recommend grounding the shield at one end or the other. I do not recommend grounding the shield at both ends. Its bad practice to have current flowing through the shield.
>
> Larry,
> K7YBZ
>
>
> --- In tracker2@yahoogroups.com, Wes Freeman <wes.freeman@> wrote:
> >
> > Hi Rob,
> >
> > There are a couple of people who have Nuvis that operate
> >
> > Mine did power up in FMI mode once, but only once.
> > I've tried powering the Nuvi before the OT2and the OT2 before
> > the Nuvi, as well as powering both simultaneously. None of these
> > combinations works for me.
> >
> > There are instructions in the files section of this newsgroup on
> > how to take your Nuvi apart and modify it to enable side-connector
> > power.
> >
> > For the rest of us, it's two connectors.
> >
> > Wes Freeman
> > KG6POV
> >
> > ve7rwn wrote:
> >
> > >I am trying to do a single plug setup for the Nuvi.
> > >I have supplied 5V to the red wire at the "bump"
> > >in the Garmin FMI cable. When it is plugged in,
> > >the Nuvi sees the power as indicated by the charge icon.
> > >However, the Nuvi will only go into FMI mode if I apply
> > >the power to the side cable after I connect the T2.
> > >Any thoughts? Because of my preffered mounting plans,
> > >I need as flush mounting as possible, and the side cable
> > >would allow this.
> > >Tnx, rob..
> > >
> > >
> > >
> > >------------------------------------
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
>
• Looks like I cannot count, saying four wires instead of five in the cable: red, yellow, black, green, and white. Sorry about that. Obviously there is a caveat
Message 2 of 13 , Apr 3, 2009
• 0 Attachment
Looks like I cannot count, saying four wires instead of five in the cable: red, yellow, black, green, and white. Sorry about that.

Obviously there is a caveat to the issue, and that is the Nuvi may never draw 500 ma. However, that is the max allotment for a high power USB device and the design calculations need to take that into consideration.

Normally, a self-powered USB hub or host will limit the current to 100 ma until it recognizes the device ID and registers the device in the device table. Once the device is validated as being a high power device, the current limit will be lifted and the device will be allowed to draw the full compliment of 500 ma. Even then, there is circuitry at the hub or host to limit current spikes.

Under normal use of the FMI cable, the Nuvi is sourcing current for the translator in the cable. By suppling power from another source through the cable, I don't know how the Nuvi will actually handle this. Yes people are using this method with success and I have seen the mods to the Nuvi that have been done, but I am not convinced there will not be damage in the long run. Until I get my hands on a 350 and look over the circuitry, I will reserve further comment.

The following is derived from the USB cable specs for those who want to play with Ohms law further:

Wire Gauge - ohms/foot max -- Vdrop @ 0.5A -- Imax for 250 mV
------------------------------- for 21 ft --- drop at 21 ft.
20 AWG ....... 0.0109 .......... 0.114V ....... 1310 mA
22 AWG ....... 0.0175 .......... 0.184V ........ 816 mA
24 AWG ....... 0.0277 .......... 0.291V ........ 515 mA
26 AWG ....... 0.0445 .......... 0.467V ........ 321 mA
28 AWG ....... 0.0707 .......... 0.742V ........ 202 mA

I hope I didn't ruffle too many feathers.

Larry,
K7YBZ

--- In tracker2@yahoogroups.com, "wt9m" <wt9m@...> wrote:
>
> Glad you did the math on this - I was wondering about the voltage drop on this since the red wire in the cable did seem pretty thin!
> Larry WT9M
>
> --- In tracker2@yahoogroups.com, "k7ybz" <k7ybz@> wrote:
> >
> > Hi boys and girls,
> >
> > There is one problem that no one has addressed when using the FMI cable to power the Nuvi and that is the cable power and ground wires are 28AWG wire. The cable itself is 10.5 ft long which means the total wire length for voltage drop is 21 ft. The minimum voltage for a high power USB device is 4.75V. With a 5V regulator the maximum voltage drop is 0.25V. (Yes, USB devices may operate at less than 4.75V but is not guaranteed.) Back to the math. The maximum current you can put through the total cable length and still be within limits is 200 ma.
> >
> > The cable has four wires with a foil shield and drain braid. The white and green wires are actually 26 AWG wire and the red, black, and yellow are 28 AWG.
> >
> > Here are some options available and still use the same cable:
> > 1. If you have a separate regulator that is adjustable, set it 5.25V. That is the maximum voltage that can be supplied to a USB device and with no current draw, the maximum voltage will not be exceeded.
> > 2. Wire the green wire in parallel with the black wire.
> > 3. Rewire the cable so that the green and white wires supply power and the signal wires use the red and yellow. Put the black wire in parallel with the ground wire you select between the green and white.
> > 4. Shorten the cable.
> > 5. Use options 1 and 2.
> > 6. Use otpions 3 and 4.
> > 7. Use options 1, 3, and 4.
> > 8. Take your pick.
> >
> > Since I have not disected the cable at the bump, I don't know if the shield is grounded at the bump. However, I recommend grounding the shield at one end or the other. I do not recommend grounding the shield at both ends. Its bad practice to have current flowing through the shield.
> >
> > Larry,
> > K7YBZ
> >
> >
> > --- In tracker2@yahoogroups.com, Wes Freeman <wes.freeman@> wrote:
> > >
> > > Hi Rob,
> > >
> > > There are a couple of people who have Nuvis that operate
> > >
> > > Mine did power up in FMI mode once, but only once.
> > > I've tried powering the Nuvi before the OT2and the OT2 before
> > > the Nuvi, as well as powering both simultaneously. None of these
> > > combinations works for me.
> > >
> > > There are instructions in the files section of this newsgroup on
> > > how to take your Nuvi apart and modify it to enable side-connector
> > > power.
> > >
> > > For the rest of us, it's two connectors.
> > >
> > > Wes Freeman
> > > KG6POV
> > >
> > > ve7rwn wrote:
> > >
> > > >I am trying to do a single plug setup for the Nuvi.
> > > >I have supplied 5V to the red wire at the "bump"
> > > >in the Garmin FMI cable. When it is plugged in,
> > > >the Nuvi sees the power as indicated by the charge icon.
> > > >However, the Nuvi will only go into FMI mode if I apply
> > > >the power to the side cable after I connect the T2.
> > > >Any thoughts? Because of my preffered mounting plans,
> > > >I need as flush mounting as possible, and the side cable
> > > >would allow this.
> > > >Tnx, rob..
> > > >
> > > >
> > > >
> > > >------------------------------------
> > > >
> > > >Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> >
>
• I ve been following this post with considerable interest. Has anyone reading this chain actually dissected the Garmin FMI cable and prepared a schematic
Message 3 of 13 , Apr 3, 2009
• 0 Attachment
I've been following this post with considerable interest. Has anyone
reading this chain actually dissected the Garmin FMI cable and prepared a
schematic diagram, end-to-end, with pinouts and color codes, and including
the "lump" circuitry, shield wires, etc? Seems like that would be a useful
reference for anyone thinking of home-brewing a powered side-mount cable
along this line or modifying the Garmin cable. Maybe the schematic is
already out there somewhere and I just haven't found it yet... anyone??
Ken W7DYX

----- Original Message -----
From: "k7ybz" <k7ybz@...>
To: <tracker2@yahoogroups.com>
Sent: Friday, April 03, 2009 12:08 PM
Subject: [tracker2] Re: Nuvi side plug

> Looks like I cannot count, saying four wires instead of five in the cable:
> red, yellow, black, green, and white. Sorry about that.
>
> Obviously there is a caveat to the issue, and that is the Nuvi may never
> draw 500 ma. However, that is the max allotment for a high power USB
> device and the design calculations need to take that into consideration.
>
> Normally, a self-powered USB hub or host will limit the current to 100 ma
> until it recognizes the device ID and registers the device in the device
> table. Once the device is validated as being a high power device, the
> current limit will be lifted and the device will be allowed to draw the
> full compliment of 500 ma. Even then, there is circuitry at the hub or
> host to limit current spikes.
>
> Under normal use of the FMI cable, the Nuvi is sourcing current for the
> translator in the cable. By suppling power from another source through the
> cable, I don't know how the Nuvi will actually handle this. Yes people are
> using this method with success and I have seen the mods to the Nuvi that
> have been done, but I am not convinced there will not be damage in the
> long run. Until I get my hands on a 350 and look over the circuitry, I
> will reserve further comment.
>
> The following is derived from the USB cable specs for those who want to
> play with Ohms law further:
>
> Wire Gauge - ohms/foot max -- Vdrop @ 0.5A -- Imax for 250 mV
> ------------------------------- for 21 ft --- drop at 21 ft.
> 20 AWG ....... 0.0109 .......... 0.114V ....... 1310 mA
> 22 AWG ....... 0.0175 .......... 0.184V ........ 816 mA
> 24 AWG ....... 0.0277 .......... 0.291V ........ 515 mA
> 26 AWG ....... 0.0445 .......... 0.467V ........ 321 mA
> 28 AWG ....... 0.0707 .......... 0.742V ........ 202 mA
>
> I hope I didn't ruffle too many feathers.
>
> Larry,
> K7YBZ
>
>
> --- In tracker2@yahoogroups.com, "wt9m" <wt9m@...> wrote:
>>
>> Glad you did the math on this - I was wondering about the voltage drop on
>> this since the red wire in the cable did seem pretty thin!
>> Larry WT9M
>>
>> --- In tracker2@yahoogroups.com, "k7ybz" <k7ybz@> wrote:
>> >
>> > Hi boys and girls,
>> >
>> > There is one problem that no one has addressed when using the FMI cable
>> > to power the Nuvi and that is the cable power and ground wires are
>> > 28AWG wire. The cable itself is 10.5 ft long which means the total wire
>> > length for voltage drop is 21 ft. The minimum voltage for a high power
>> > USB device is 4.75V. With a 5V regulator the maximum voltage drop is
>> > 0.25V. (Yes, USB devices may operate at less than 4.75V but is not
>> > guaranteed.) Back to the math. The maximum current you can put through
>> > the total cable length and still be within limits is 200 ma.
>> >
>> > The cable has four wires with a foil shield and drain braid. The white
>> > and green wires are actually 26 AWG wire and the red, black, and yellow
>> > are 28 AWG.
>> >
>> > Here are some options available and still use the same cable:
>> > 1. If you have a separate regulator that is adjustable, set it 5.25V.
>> > That is the maximum voltage that can be supplied to a USB device and
>> > with no current draw, the maximum voltage will not be exceeded.
>> > 2. Wire the green wire in parallel with the black wire.
>> > 3. Rewire the cable so that the green and white wires supply power and
>> > the signal wires use the red and yellow. Put the black wire in parallel
>> > with the ground wire you select between the green and white.
>> > 4. Shorten the cable.
>> > 5. Use options 1 and 2.
>> > 6. Use otpions 3 and 4.
>> > 7. Use options 1, 3, and 4.
>> > 8. Take your pick.
>> >
>> > Since I have not disected the cable at the bump, I don't know if the
>> > shield is grounded at the bump. However, I recommend grounding the
>> > shield at one end or the other. I do not recommend grounding the shield
>> > at both ends. Its bad practice to have current flowing through the
>> > shield.
>> >
>> > Larry,
>> > K7YBZ
>> >
>> >
>> > --- In tracker2@yahoogroups.com, Wes Freeman <wes.freeman@> wrote:
>> > >
>> > > Hi Rob,
>> > >
>> > > There are a couple of people who have Nuvis that operate
>> > >
>> > > Mine did power up in FMI mode once, but only once.
>> > > I've tried powering the Nuvi before the OT2and the OT2 before
>> > > the Nuvi, as well as powering both simultaneously. None of these
>> > > combinations works for me.
>> > >
>> > > There are instructions in the files section of this newsgroup on
>> > > how to take your Nuvi apart and modify it to enable side-connector
>> > > power.
>> > >
>> > > For the rest of us, it's two connectors.
>> > >
>> > > Wes Freeman
>> > > KG6POV
>> > >
>> > > ve7rwn wrote:
>> > >
>> > > >I am trying to do a single plug setup for the Nuvi.
>> > > >I have supplied 5V to the red wire at the "bump"
>> > > >in the Garmin FMI cable. When it is plugged in,
>> > > >the Nuvi sees the power as indicated by the charge icon.
>> > > >However, the Nuvi will only go into FMI mode if I apply
>> > > >the power to the side cable after I connect the T2.
>> > > >Any thoughts? Because of my preffered mounting plans,
>> > > >I need as flush mounting as possible, and the side cable
>> > > >would allow this.
>> > > >Tnx, rob..
>> > > >
>> > > >
>> > > >
>> > > >------------------------------------
>> > > >
>> > > >Yahoo! Groups Links
>> > > >
>> > > >
>> > > >
>> > > >
>> > > >
>> > > >
>> > >
>> >
>>
>
>
>
>
> ------------------------------------
>
>
>
>
• I think I ve got all of that in various chicken scratchings on multiple notepads, plus some microscope camera pictures of the PCB itself. If I can find all of
Message 4 of 13 , Apr 3, 2009
• 0 Attachment
I think I've got all of that in various chicken scratchings on multiple
notepads, plus some microscope camera pictures of the PCB itself. If I
can find all of that, I'll dump it on the wiki and let someone else
clean it up a bit.

Scott

Ken & Cece Westby wrote:
>
>
> I've been following this post with considerable interest. Has anyone
> reading this chain actually dissected the Garmin FMI cable and prepared a
> schematic diagram, end-to-end, with pinouts and color codes, and including
> the "lump" circuitry, shield wires, etc? Seems like that would be a useful
> reference for anyone thinking of home-brewing a powered side-mount cable
> along this line or modifying the Garmin cable. Maybe the schematic is
> already out there somewhere and I just haven't found it yet... anyone??
> Ken W7DYX
>
> ----- Original Message -----
> From: "k7ybz" <k7ybz@... <mailto:k7ybz%40arrl.net>>
> To: <tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>>
> Sent: Friday, April 03, 2009 12:08 PM
> Subject: [tracker2] Re: Nuvi side plug
>
> > Looks like I cannot count, saying four wires instead of five in the
> cable:
> > red, yellow, black, green, and white. Sorry about that.
> >
> > Obviously there is a caveat to the issue, and that is the Nuvi may never
> > draw 500 ma. However, that is the max allotment for a high power USB
> > device and the design calculations need to take that into consideration.
> >
> > Normally, a self-powered USB hub or host will limit the current to
> 100 ma
> > until it recognizes the device ID and registers the device in the device
> > table. Once the device is validated as being a high power device, the
> > current limit will be lifted and the device will be allowed to draw the
> > full compliment of 500 ma. Even then, there is circuitry at the hub or
> > host to limit current spikes.
> >
> > Under normal use of the FMI cable, the Nuvi is sourcing current for the
> > translator in the cable. By suppling power from another source
> through the
> > cable, I don't know how the Nuvi will actually handle this. Yes
> people are
> > using this method with success and I have seen the mods to the Nuvi that
> > have been done, but I am not convinced there will not be damage in the
> > long run. Until I get my hands on a 350 and look over the circuitry, I
> > will reserve further comment.
> >
> > The following is derived from the USB cable specs for those who want to
> > play with Ohms law further:
> >
> > Wire Gauge - ohms/foot max -- Vdrop @ 0.5A -- Imax for 250 mV
> > ------------------------------- for 21 ft --- drop at 21 ft.
> > 20 AWG ....... 0.0109 .......... 0.114V ....... 1310 mA
> > 22 AWG ....... 0.0175 .......... 0.184V ........ 816 mA
> > 24 AWG ....... 0.0277 .......... 0.291V ........ 515 mA
> > 26 AWG ....... 0.0445 .......... 0.467V ........ 321 mA
> > 28 AWG ....... 0.0707 .......... 0.742V ........ 202 mA
> >
> > I hope I didn't ruffle too many feathers.
> >
> > Larry,
> > K7YBZ
> >
> >
> > --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
> "wt9m" <wt9m@...> wrote:
> >>
> >> Glad you did the math on this - I was wondering about the voltage
> drop on
> >> this since the red wire in the cable did seem pretty thin!
> >> Larry WT9M
> >>
> >> --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
> "k7ybz" <k7ybz@> wrote:
> >> >
> >> > Hi boys and girls,
> >> >
> >> > There is one problem that no one has addressed when using the FMI
> cable
> >> > to power the Nuvi and that is the cable power and ground wires are
> >> > 28AWG wire. The cable itself is 10.5 ft long which means the total
> wire
> >> > length for voltage drop is 21 ft. The minimum voltage for a high
> power
> >> > USB device is 4.75V. With a 5V regulator the maximum voltage drop is
> >> > 0.25V. (Yes, USB devices may operate at less than 4.75V but is not
> >> > guaranteed.) Back to the math. The maximum current you can put
> through
> >> > the total cable length and still be within limits is 200 ma.
> >> >
> >> > The cable has four wires with a foil shield and drain braid. The
> white
> >> > and green wires are actually 26 AWG wire and the red, black, and
> yellow
> >> > are 28 AWG.
> >> >
> >> > Here are some options available and still use the same cable:
> >> > 1. If you have a separate regulator that is adjustable, set it 5.25V.
> >> > That is the maximum voltage that can be supplied to a USB device and
> >> > with no current draw, the maximum voltage will not be exceeded.
> >> > 2. Wire the green wire in parallel with the black wire.
> >> > 3. Rewire the cable so that the green and white wires supply power
> and
> >> > the signal wires use the red and yellow. Put the black wire in
> parallel
> >> > with the ground wire you select between the green and white.
> >> > 4. Shorten the cable.
> >> > 5. Use options 1 and 2.
> >> > 6. Use otpions 3 and 4.
> >> > 7. Use options 1, 3, and 4.
> >> > 8. Take your pick.
> >> >
> >> > Since I have not disected the cable at the bump, I don't know if the
> >> > shield is grounded at the bump. However, I recommend grounding the
> >> > shield at one end or the other. I do not recommend grounding the
> shield
> >> > at both ends. Its bad practice to have current flowing through the
> >> > shield.
> >> >
> >> > Larry,
> >> > K7YBZ
> >> >
> >> >
> >> > --- In tracker2@yahoogroups.com
> <mailto:tracker2%40yahoogroups.com>, Wes Freeman <wes.freeman@> wrote:
> >> > >
> >> > > Hi Rob,
> >> > >
> >> > > There are a couple of people who have Nuvis that operate
> >> > >
> >> > > Mine did power up in FMI mode once, but only once.
> >> > > I've tried powering the Nuvi before the OT2and the OT2 before
> >> > > the Nuvi, as well as powering both simultaneously. None of these
> >> > > combinations works for me.
> >> > >
> >> > > There are instructions in the files section of this newsgroup on
> >> > > how to take your Nuvi apart and modify it to enable side-connector
> >> > > power.
> >> > >
> >> > > For the rest of us, it's two connectors.
> >> > >
> >> > > Wes Freeman
> >> > > KG6POV
> >> > >
> >> > > ve7rwn wrote:
> >> > >
> >> > > >I am trying to do a single plug setup for the Nuvi.
> >> > > >I have supplied 5V to the red wire at the "bump"
> >> > > >in the Garmin FMI cable. When it is plugged in,
> >> > > >the Nuvi sees the power as indicated by the charge icon.
> >> > > >However, the Nuvi will only go into FMI mode if I apply
> >> > > >the power to the side cable after I connect the T2.
> >> > > >Any thoughts? Because of my preffered mounting plans,
> >> > > >I need as flush mounting as possible, and the side cable
> >> > > >would allow this.
> >> > > >Tnx, rob..
> >> > > >
> >> > > >
> >> > > >
> >> > > >------------------------------------
> >> > > >
> >> > > >Yahoo! Groups Links
> >> > > >
> >> > > >
> >> > > >
> >> > > >
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> >
> >
> >
> >
> > ------------------------------------
> >
> >
> >
> >
>
>
• I had a non-group email from a colleague telling me the white and green wires are 28 gauge and not 26 gauge. Its just that the insulation thickness is
Message 5 of 13 , Apr 4, 2009
• 0 Attachment
I had a non-group email from a colleague telling me the white and green wires are 28 gauge and not 26 gauge. Its just that the insulation thickness is different (thicker) on the signal wires than the other wires. The USB cabling spec does say the nominal insulation thickness on the signal wires is 0.012" and the nominal insulation thickness on the power wires is 0.010". This would make more sense, and again I appologize.

Larry
K7YBZ

--- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
>
> I think I've got all of that in various chicken scratchings on multiple
> notepads, plus some microscope camera pictures of the PCB itself. If I
> can find all of that, I'll dump it on the wiki and let someone else
> clean it up a bit.
>
> Scott
>
> Ken & Cece Westby wrote:
> >
> >
> > I've been following this post with considerable interest. Has anyone
> > reading this chain actually dissected the Garmin FMI cable and prepared a
> > schematic diagram, end-to-end, with pinouts and color codes, and including
> > the "lump" circuitry, shield wires, etc? Seems like that would be a useful
> > reference for anyone thinking of home-brewing a powered side-mount cable
> > along this line or modifying the Garmin cable. Maybe the schematic is
> > already out there somewhere and I just haven't found it yet... anyone??
> > Ken W7DYX
> >
> > ----- Original Message -----
> > From: "k7ybz" <k7ybz@... <mailto:k7ybz%40arrl.net>>
> > To: <tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>>
> > Sent: Friday, April 03, 2009 12:08 PM
> > Subject: [tracker2] Re: Nuvi side plug
> >
> > > Looks like I cannot count, saying four wires instead of five in the
> > cable:
> > > red, yellow, black, green, and white. Sorry about that.
> > >
> > > Obviously there is a caveat to the issue, and that is the Nuvi may never
> > > draw 500 ma. However, that is the max allotment for a high power USB
> > > device and the design calculations need to take that into consideration.
> > >
> > > Normally, a self-powered USB hub or host will limit the current to
> > 100 ma
> > > until it recognizes the device ID and registers the device in the device
> > > table. Once the device is validated as being a high power device, the
> > > current limit will be lifted and the device will be allowed to draw the
> > > full compliment of 500 ma. Even then, there is circuitry at the hub or
> > > host to limit current spikes.
> > >
> > > Under normal use of the FMI cable, the Nuvi is sourcing current for the
> > > translator in the cable. By suppling power from another source
> > through the
> > > cable, I don't know how the Nuvi will actually handle this. Yes
> > people are
> > > using this method with success and I have seen the mods to the Nuvi that
> > > have been done, but I am not convinced there will not be damage in the
> > > long run. Until I get my hands on a 350 and look over the circuitry, I
> > > will reserve further comment.
> > >
> > > The following is derived from the USB cable specs for those who want to
> > > play with Ohms law further:
> > >
> > > Wire Gauge - ohms/foot max -- Vdrop @ 0.5A -- Imax for 250 mV
> > > ------------------------------- for 21 ft --- drop at 21 ft.
> > > 20 AWG ....... 0.0109 .......... 0.114V ....... 1310 mA
> > > 22 AWG ....... 0.0175 .......... 0.184V ........ 816 mA
> > > 24 AWG ....... 0.0277 .......... 0.291V ........ 515 mA
> > > 26 AWG ....... 0.0445 .......... 0.467V ........ 321 mA
> > > 28 AWG ....... 0.0707 .......... 0.742V ........ 202 mA
> > >
> > > I hope I didn't ruffle too many feathers.
> > >
> > > Larry,
> > > K7YBZ
> > >
> > >
> > > --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
> > "wt9m" <wt9m@> wrote:
> > >>
> > >> Glad you did the math on this - I was wondering about the voltage
> > drop on
> > >> this since the red wire in the cable did seem pretty thin!
> > >> Larry WT9M
> > >>
> > >> --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
> > "k7ybz" <k7ybz@> wrote:
> > >> >
> > >> > Hi boys and girls,
> > >> >
> > >> > There is one problem that no one has addressed when using the FMI
> > cable
> > >> > to power the Nuvi and that is the cable power and ground wires are
> > >> > 28AWG wire. The cable itself is 10.5 ft long which means the total
> > wire
> > >> > length for voltage drop is 21 ft. The minimum voltage for a high
> > power
> > >> > USB device is 4.75V. With a 5V regulator the maximum voltage drop is
> > >> > 0.25V. (Yes, USB devices may operate at less than 4.75V but is not
> > >> > guaranteed.) Back to the math. The maximum current you can put
> > through
> > >> > the total cable length and still be within limits is 200 ma.
> > >> >
> > >> > The cable has four wires with a foil shield and drain braid. The
> > white
> > >> > and green wires are actually 26 AWG wire and the red, black, and
> > yellow
> > >> > are 28 AWG.
> > >> >
> > >> > Here are some options available and still use the same cable:
> > >> > 1. If you have a separate regulator that is adjustable, set it 5.25V.
> > >> > That is the maximum voltage that can be supplied to a USB device and
> > >> > with no current draw, the maximum voltage will not be exceeded.
> > >> > 2. Wire the green wire in parallel with the black wire.
> > >> > 3. Rewire the cable so that the green and white wires supply power
> > and
> > >> > the signal wires use the red and yellow. Put the black wire in
> > parallel
> > >> > with the ground wire you select between the green and white.
> > >> > 4. Shorten the cable.
> > >> > 5. Use options 1 and 2.
> > >> > 6. Use otpions 3 and 4.
> > >> > 7. Use options 1, 3, and 4.
> > >> > 8. Take your pick.
> > >> >
> > >> > Since I have not disected the cable at the bump, I don't know if the
> > >> > shield is grounded at the bump. However, I recommend grounding the
> > >> > shield at one end or the other. I do not recommend grounding the
> > shield
> > >> > at both ends. Its bad practice to have current flowing through the
> > >> > shield.
> > >> >
> > >> > Larry,
> > >> > K7YBZ
> > >> >
> > >> >
> > >> > --- In tracker2@yahoogroups.com
> > <mailto:tracker2%40yahoogroups.com>, Wes Freeman <wes.freeman@> wrote:
> > >> > >
> > >> > > Hi Rob,
> > >> > >
> > >> > > There are a couple of people who have Nuvis that operate
> > >> > > properly when powered by the side connector.
> > >> > >
> > >> > > Mine did power up in FMI mode once, but only once.
> > >> > > I've tried powering the Nuvi before the OT2and the OT2 before
> > >> > > the Nuvi, as well as powering both simultaneously. None of these
> > >> > > combinations works for me.
> > >> > >
> > >> > > There are instructions in the files section of this newsgroup on
> > >> > > how to take your Nuvi apart and modify it to enable side-connector
> > >> > > power.
> > >> > >
> > >> > > For the rest of us, it's two connectors.
> > >> > >
> > >> > > Wes Freeman
> > >> > > KG6POV
> > >> > >
> > >> > > ve7rwn wrote:
> > >> > >
> > >> > > >I am trying to do a single plug setup for the Nuvi.
> > >> > > >I have supplied 5V to the red wire at the "bump"
> > >> > > >in the Garmin FMI cable. When it is plugged in,
> > >> > > >the Nuvi sees the power as indicated by the charge icon.
> > >> > > >However, the Nuvi will only go into FMI mode if I apply
> > >> > > >the power to the side cable after I connect the T2.
> > >> > > >Any thoughts? Because of my preffered mounting plans,
> > >> > > >I need as flush mounting as possible, and the side cable
> > >> > > >would allow this.
> > >> > > >Tnx, rob..
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > >------------------------------------
> > >> > > >
> > >> > > >Yahoo! Groups Links
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > >
> > >> >
> > >>
> > >
> > >
> > >
> > >
> > > ------------------------------------
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> >
> >
>
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