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| cb1rocket |
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cb1rocket
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| Teflon-Mike |
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Teflon-Mike
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 Posted: 12:39 - 19 Aug 2011  Post subject: Re: GPS charger using a 6v bike? |
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| cb1rocket wrote: | Will it work? I know the charger is basically a regulator to reduce from 12v but will it work from a 6v source?
Cheers |
Whats the DC power supply voltage on a USB cable (I actually have no idea!) probably something like 3v or 5.
Whats the power supply rating on the GPS? most likely same as a phone, something like 3.4 or 5.2v or something.
12v Car charger will be a simple step down transformer, that will 'drop' volts from 12v to say 3.4 on a multiplication basis, by the number of windings on input and output coils, or by ratio of resistors in a network.
So electronics of car charger to drop volts from 12v to 3v on cars power supply, gives 4:1 reduction; plug that into 6v supply, you'll probably still get 4:1 reduction and 1.5v, or half what you need to run equipment.
So, short answer...... I doubt it.
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Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| DrDonnyBrago |
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DrDonnyBrago
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| Posted: 13:38 - 19 Aug 2011 Post subject: Re: GPS charger using a 6v bike? |
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I reckon a 5v regulator would do the trick? Head down maplins and have a word with the parts guy.
i.e.
https://www.ebay.co.uk/itm/L7805CV-Voltage-Regulator-5V-10pk-less-than-20p-ea-/390335454744?pt=LH_DefaultDomain_3&hash=item5ae1ce5e18#ht_500wt_922
Most of the 5v regulators I have come across need a c.8v supply and min 7/8v input (max 35v) but if you could find the right regulator (i.e. one with a minimum of 6v) you should get a stable 5v output. the drop from 6v to 5v isnt much but I'd probably want to heat sink it anyway (i.e. fix it to something made of metal to help it cool).
All you would then need to do is fashion a 5v USB port for a 6v supply using a regulator and a female USB end... That way you would just need to plug the GPS in using a usb cable.
P.s. the one in the link I posted doesn't say min input voltage - it'd probably be safe to assume it is unsuitable.
Last edited by DrDonnyBrago on 13:42 - 19 Aug 2011; edited 1 time in total |
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| Charlie |
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Charlie
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| Posted: 13:40 - 19 Aug 2011 Post subject: |
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My experience with voltage regulators is that they try to clamp the voltage to 5v rather reducing via ratios as Mike has said... Although I guess this depends on the type of voltage regulation.
I am assuming that 12v sockets don't do anything to the electronic signal (i.e. they really are just a socket), then you could do an experiment and see what happens. Don't plug in your GPS, use a multi-meter to see if there is 5v coming out. Undervoltage won't harm the charger (I think).
https://www.homebrewusb.com/DIY/Images/pinoutUSB.jpg
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Last edited by Charlie on 13:44 - 19 Aug 2011; edited 1 time in total |
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| cb1rocket |
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cb1rocket
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| Charlie |
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Charlie
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| cb1rocket |
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cb1rocket
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| Codemonkey |
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Codemonkey
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| Posted: 14:18 - 19 Aug 2011 Post subject: Re: GPS charger using a 6v bike? |
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| Teflon-Mike wrote: | 12v Car charger will be a simple step down transformer, that will 'drop' volts from 12v to say 3.4 on a multiplication basis, by the number of windings on input and output coils, or by ratio of resistors in a network. |
Transformers only work on AC power, not DC.
Anything that drops voltage down on DC is likely to be just a regulator (unless its a big drop, like 110v dc down to 5vdc), and anything that steps DC up to a higher level is known as a DC to DC convertor (they convert DC to AC, then use a transformer to step the voltage up, then convert to DC again before regulating the final output voltage).
In the case of running a 5V USB charger from a 6V battery, it depends a lot on the regulator in the charger and its "dropout" voltage. The dropout voltage is the minimum amount of volts dropped across the regulator, and on many simple devices is in the region of 1.2V, so to get 5V you'd have to have a minimum of 6.2V supply, which you probably will since the battery should be above 6V while charging.
You can get cheap cigarette socket to USB adapters from Maplins for just a few quid, they plug into the cig socket almost completely and just leave you with a USB socket. I'd be tempted to just get one of those and hard wire it in (make sure you fit an inline fuse though, otherwise if it fails, they tend to go short circuit and could either burn the wiring out or pass the 6V+ straight through to your phone/satnav etc).
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| Teflon-Mike |
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Teflon-Mike
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| Posted: 16:15 - 19 Aug 2011 Post subject: |
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Another thought; Snowie's Garmin is powered from USB plug.
HOWEVER: I dont know how its wired to do it, but on the garmin's car adaptor, powers up and 'runs' off the power supply, so works as GPS tracking as it charges.
Plug it into USB cable off the 'puter, and it auto connects
Plug it into cheap 'generic' USB power supply, goes into 'Charge' mode and starts charging; WONT display maps or GPS track....
IE you have to use genuine Garmin power supply, or compatible copy (Got a couple of e-bay £2 post free! FFS how cheap is THAT!)
Other thought using voltage regulators; six volt supply on most 6v bikes is pretty 'dirty', and not very stable. Usually low amp output, and with seperate widings, often three, one powering sparks, one the lights, third charging battery & powering 'equipment'.
Frequently dont have many spare amps; (Though GPS would draw little, regulator may!)
And regulator might have tough time with alternating DC supply ramping from zero to sometimes 10-14v, depending on revs, not at a fixed frequency... depends where you take volts from though.... battery can damp it a bit.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| Charlie |
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Charlie
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| Posted: 18:55 - 19 Aug 2011 Post subject: |
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A 100nF capacitor to decouple would remove some of the noise as well. 
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cb1rocket
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Old Thread Alert!
The last post was made 14 years, 176 days ago. Instead of replying here, would creating a new thread be more useful? |
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