Whilst in the process of fitting a Garmin satnav cradle to my D Comet (replica) I discover that it is wired for +earth, is this a particularly good thing, what are the pros and cons if there are any, and if so what is involved in changing to -earth, it is running a Lucas dynamo, everything else is pretty much standard, I don't think it is relying on the headset bearings to provide an electric path, a cable has been run to the headlamp.
Misc: Charging Systems Positive Earth
- Thread starter Peter Holmes
- Start date
Years ago + earth and - earth didn't really make a difference, but today with satnav, LED headlights etc it does. To change the bike's polarity to -ve earth you will need to swap the leads over on the ammerter terminals and also the battery terminals. The main thing and biggest cost though is the dynamo regulator will need changing to a -ve earth type and you will probably have to alter the internal wring of the dynamo to change the dynamo output polarity.
The alternative is to make sure the Garmin is totally isolated from the bike electrically and then you can wire the +ve & -ve leads from the Garmin to the approprite connections on the bike observing their polarity in relation to the bike.
Simon
The alternative is to make sure the Garmin is totally isolated from the bike electrically and then you can wire the +ve & -ve leads from the Garmin to the approprite connections on the bike observing their polarity in relation to the bike.
Simon
Thanks Simon, just the info that I needed, so LED indicators are polarity conscious, I was not aware of that, I was thinking of fitting Kellermann Atto indicators, very small, effective and unobtrusive, oh nearly forgot, and bloody expensive, but I do dislike the huge indicators that were fitted to bikes when they first became popular.
Most LED lights are polarity conscious but I have seen some clever ones that can cope with either polarity and so they must have some extra electronics inside the package to cope.
Usually an indicator relay nowdays is a solid state electronic item and not electro-mechanical, especially for LED lights, and so will be polarity conscious.
Simon
Usually an indicator relay nowdays is a solid state electronic item and not electro-mechanical, especially for LED lights, and so will be polarity conscious.
Simon
Another thing to be aware of is most Garmin today run of 5V as you can plug them straight into your computer via a USB cable and USB is 5V. The lead for use in a car usually has the cigarette lighter plug in the end of the lead which converts the 12V from the car to 5V. On the motorbike version this is a small black box which you mount somwhere on the bike and connect to the GPS cradle and converts the 12V to 5V. If you do feed 12V direct into the Garmin and so bypass the convertor then your Garmin will fail.
Now you may be lucky as some GPS units take 12V direct into the unit but those usually have a different connector so you cannot plug a USB or micro USB lead into it.
Now you may be lucky as some GPS units take 12V direct into the unit but those usually have a different connector so you cannot plug a USB or micro USB lead into it.
Not wanting to nit pick Tim, but by comparison to the Kellermann Atto's they are huge, I first saw the Kellermann's when I visited the Godet workshops, they are really nice and very effective, and as I said previously, very expensive, but I suppose the motto could be "do it once, do it right"
Well at between £46 and £87 each (times four for a complete bike)they should be remarkable. I like my two inch diameter ones.
2 inches, Christ at that size do you have to increase your tyre pressures?