A little bit of a background. I spend alot of time in the great outdoors far away from most forms of electronic communications, but, I do carry my GPS with me. When I am in one of my Jeeps or have my solar-powered camping-trailer along, I have a way to keep my GPS charged up and running. When I am out there with just a tent and my Kawasaki KLR650, I need a reliable way to keep my GPS (and similar electronics) functional.

In my attempt to keep my GPS running, I hardwired-in a "weather proof 12-volt to USB converter" from PrincessAuto ( http://www.princessauto.com/pal/pro...ous-Automotive/Weather-Proof-USB-Power-Outlet ) (kind of Canadian version of TractorSupply or HarborFreight). The problem that I have run into is the fact that when I am riding my motorbike, the GPS tries to shut-down and then start-up and then shut-down again - and the cycle repeats often. I have tried two different GPS's and four different connector cords to try to fix the problem and I have not had any difference between the different manufacturers (Garmin and Magellan).

I have checked all the connections with a volt-meter and wiggled everything all around and I haven't had any success in finding a bad connection anywhere. For those who might have a KLR, I have my USB converter wired into the "City Lights" circuit.

What I am looking to do is have a 12-volt based UPS (Uninteruptable Power Supply), but, because I am on a motorbike, I need something that would be weather-proof, shock proof (shock as in vibration or falling over) and I need it to be simple to work on deep in the back-country if something were to fail.

What I am thinking of doing is using a fairly small "Radio Shack" project box that I can seal-up and running the positive and negative leads into the box to a basic project circuit board. At the start of the circuit board, I would like to put a red LED to show that power is flowing from the bike to the project box - that LED might flash if there are power-drops - but - it would be used primarily as a basic diode for flow-control of the power. From that LED, I would like to put a small bank of capacitators (I was thinking of ten 1000 micro-farad capacitators because I can buy them fairly locally for about $5) and then put a second LED on the "exit-side" of the project box (lets call this one green) to show that power is flowing properly through the project box to the USB connector. If things go well, the green LED will never flash like I would expect the red one to do.

Does anyone see any problems with doing something like this - any issues with vibration from a large single-cylinder motorcycle that travels gravel-roads / trails for fun?

 

Just wire up a "cigarette outlet" to the "city lights" circuit and buy a 12V to usb cig adapter? Stick that in a project box..

Maybe though this is a stator/RPM issue where its really not a constant 12V.. Hence why your 12V-USB was power cycling..
I'd measure that 12V circuit when idling/reving,etc.. to ensure a constant 12V

 

How much current does the GPS use?

Vehicle electrical systems are horribly noisy. You probably aren't having "drop-outs". It's just the GPS getting confused by the voltage spikes. Start by giving the GPS a private wire all the way to the negative battery terminal (the black one on the adapter). Then go, battery, fuse, diode, capacitor...then the usb device.

If you need less than 1 amp, a 1N4007 diode will work.
If you have some voltage to "waste" you can do a second stage of filtering by adding a resistor (maybe just a few ohms) in series with the current, then another capacitor to ground and parallel that with a 16 volt zener diode.

Get the picture? You're making an electrical "quiet zone" for the GPS to live in.

 

One of my GPS's is a Magellan eXplorist 400 - waterproof (and everything proof) with an internal battery that I can use when hiking. Unsure how much power it takes, but, it can charge the internal battery off of a basic USB-connection - either on a computer or via "iPhone" power-converter. The other GPS is a Garmin Nuvi 550 that has very similar power-requirement specs - again it can charge-up via any USB from computer or iPhone-charger. I haven't measured how much current it requires to charge / run either of the GPS-units, but, I would imagine that it isn't significant.

In my Jeeps I use a standard power-port to USB converter or I can use the supplied stock cigarette-lighter-to-USB converter that comes with the Garmin. Both of the GPS's run "forever" without any issues in any of my Jeeps.

I have run my motorbike (in my garage) with a sliced USB cable with a volt-meter attached and it showed a very steady 5.43v with no visible power-drops. I have also run the bike's moter in my garage with leads attached to my BatteryTender leads - again - voltage seems to hold fairly steady and true.

Sometimes I can ride my bike for 15 minutes before power issues show up, sometimes it will be 1/2hr and other times it happens after 3 minutes. I could imagine that the voltage regulator under the seat of my bike could be spiking or dropping power, but, if that was the case, wouldn't my dash lights or my other lights show problems as well?

I agree that vehicle power systems are very noisy and that could be confusing a GPS, but, why would everything be fine in a freakin' old Jeep and not in a "new" motorcycle? Bigger battery, more ground-connections or some other reason why the Jeep runs better than the bike?

I wish that I had a power logging style of Fluke meter and then go for a long ride and record all forms of any possible fluctuations, but, as I don't have one available to me, I am only guessing at what I could do to clean up the signal through the bike's wiring to the GPS ...

 

The question about current is to determine how much resistance you might put in series with the second stage of filtering. If it's a whole amp, 10 ohms would use up so much voltage that your GPS wouldn't charge.

The fact that the GPS has its own battery would seem to eliminate voltage jitter and spikes from getting to the brain chip, but it doesn't. Still, the delay time before faults start happening seems to be the important part. There is no harm in providing a nicely filtered supply but I think this is not the cure. Something is changing, 3 or 15 or 30 minutes after you start the motor, and a filter probably won't fix it.

Good thing my signature line says,

 

According to the USB-specifications, computers can run upto 900mA on the USB port. Some of the new specifications state that charging can be provided by an upto 10watt charger, based on the tried-n-true math - that puts it at about 2amp ...

Now we seem to be getting away from my original question about keeping the power flowing to the USB-port in case there is some kind of power fluctuation. A friend of mine has in his car a boomin' stereo and he runs a dedicated second battery (Optima) and three 1-farad capacitators to keep his amps happily pounding out the sounds. He gave me the idea of using a couple of smallish capacitators to smooth-out the power going to the USB-port.

All I am hoping to do is "charge-up" the caps and to make sure that the power flows only one direction from the motorcycle battery towards the USB-port - if there happens to be a power drop for whatever reason, I would like to have about a 10-second "buffer" of power so that the GPS doesn't go into shut-down mode.

Would I really need to go the route of the resistor due to the fact that the capacitators will not flow more power than what the 12-volt-based circuit would provide anyway and the power would flow freely through the capacitators unless there was a reason for them to discharge ...

I know - super simplistic here....

 

Suffering from brain fry. Must go to bed now. After 11 pm (at my house) and a long day of fixing plumbing.

Other helpers please feel free to chime in.

 

Suffering from brain fry. Must go to bed now. After 11 pm (at my house) and a long day of fixing plumbing.

Other helpers please feel free to chime in.

Sleep-well - I might just build a simple test-bed for this and see what happens - worst case I burn down my house, best case, it actually works ...

 

Just to think outside the box, could there be mechanical issues that only manifest when on your bike? Are the USB data pins wired, so that there could be an unintended data signal of some kind causing havoc? Any heat on the GPS unit or USB voltage regulator? BTW, your 5.4 volts is a bit high.

Is your bike's charger based on a magneto, instead of an alternator in the Jeep?
Can you tell if your anomaly is coincident with the bike's charging switching off? There might be quite a spike when that happens.

 

Just to think outside the box, could there be mechanical issues that only manifest when on your bike? Are the USB data pins wired, so that there could be an unintended data signal of some kind causing havoc? Any heat on the GPS unit or USB voltage regulator? BTW, your 5.4 volts is a bit high.

Is your bike's charger based on a magneto, instead of an alternator in the Jeep?
Can you tell if your anomaly is coincident with the bike's charging switching off? There might be quite a spike when that happens.

The USB-port is mounted to the inside of my fairing about as far away from any heat-sources as possible - ahead of my radiator and such. Yes, there will be some heat from the headlight, but, the USB-unit is shielded from the headlight by a plastic-wall.

Mechanical issues are always possible, but, the bike is in "perfect" working condition - well as perfect as can be expected with approx. 18,000km on the clock. The KLR runs on a stator-based charging system that runs through a basic regulator/rectifier or directly through the CDI-unit (basically the brains of the bike).

If you take a peak at the wiring-diagram (attached) you will see a bit of wiring over on the far left side of near the headlight and horn with a title of NC attached to it - that is also known the CityLight circuit due to the use of those wires to run the euro-spec driving-lights (which I have on another wiring diagram if you wish to see it). That is the wiring that I am directly attached to (via bullet-connector) for my USB-power.

As far as the voltage goes, I believe that it should be approx. 5 volt plus-or-minus 5%. On my first couple of tests, it showed as 5.3 volt and a couple of the tests showed 5.4 volt ... it could be just the position on the dial that I picked on my multi-meter or maybe just the way I was holding the wires in place might have skewed the reading a little bit.


I wish that I had a way to tell if the regulator was shunting too much power when it kicks in-n-out during the charging phases, but, alas I do not have tools that would allow me to log those kinds of things. If I could program something that would allow my linux-based laptop to write the data to an OpenOffice-based spread-sheet, I would do that ...

 

This filter includes a diode to keep the charge from backing out of the capacitor if the power supply drops out.

 

#12 - that is the basic schematic that I was thinking of - BruteForce filter ... what a wonderful name!

 

That's the basic schematic I was thinking about all along.