Connecting GPS



33 replies to this topic
  • PBDBLUE

Posted January 07, 2004 - 08:01 AM

#21

First let me say that the circuit described by Toyota will work as long as the device does not require good voltage regulation. Most of the GPS's that run off 12 volts like the Magellan Sporttrak Topo have a wide input voltage spec. Just be sure to include the electrolytic cap on the DC side of the bridge rectifier because if you don't you will get some very high spikes (the open voltage output of the magneto is >50 volts). The risk with a circuit like this is that there is no protection included. If the AC regulator or a diode fails you will likely fry your GPS as the DC voltage will climb to the full output voltage of the magneto or maybe just send AC to your GPS. Either case would probably not be good for the GPS. If you decide to go this route at least put a fuse (maybe 1/2 amp) in the lead (yellow wire) coming from the magneto. The Etrex is a different animal as it is spec'd at 3.0 volts +/- .5 volts. Using a resistor in line does not provide a constant voltage to the GPS. It will vary as conditions change (i.e. - input voltage, current load, etc) and I would not recommend it. A better solution is to use a voltage regulator like an LM317 ($1.99 at Radio Shack) and a few resistors/capacitors to build a regulated power supply. It is a very simple circuit (not much more involved than the one Toyota described earlier) that will provide a stable source of regulated 3 VDC. I don't have any means of posting a picture but if you PM me I'll draw up a schematic and email it to you. I'm not trying to rain on the parade here, I'm just trying to make sure everyone is aware of the potential problems before they risk they're prized electronics. BTW - I'm a retired engineer.

  • 5spoke

Posted January 07, 2004 - 08:24 AM

#22

First let me say that the circuit described by Toyota will work as long as the device does not require good voltage regulation. Most of the GPS's that run off 12 volts like the Magellan Sporttrak Topo have a wide input voltage spec. Just be sure to include the electrolytic cap on the DC side of the bridge rectifier because if you don't you will get some very high spikes (the open voltage output of the magneto is >50 volts). The risk with a circuit like this is that there is no protection included. If the AC regulator or a diode fails you will likely fry your GPS as the DC voltage will climb to the full output voltage of the magneto or maybe just send AC to your GPS. Either case would probably not be good for the GPS. If you decide to go this route at least put a fuse (maybe 1/2 amp) in the lead (yellow wire) coming from the magneto. The Etrex is a different animal as it is spec'd at 3.0 volts +/- .5 volts. Using a resistor in line does not provide a constant voltage to the GPS. It will vary as conditions change (i.e. - input voltage, current load, etc) and I would not recommend it. A better solution is to use a voltage regulator like an LM317 ($1.99 at Radio Shack) and a few resistors/capacitors to build a regulated power supply. It is a very simple circuit (not much more involved than the one Toyota described earlier) that will provide a stable source of regulated 3 VDC. I don't have any means of posting a picture but if you PM me I'll draw up a schematic and email it to you. I'm not trying to rain on the parade here, I'm just trying to make sure everyone is aware of the potential problems before they risk they're prized electronics. BTW - I'm a retired engineer.


I agree with you Pbdblue 100% about coming off the AC circuit...The resistor’s would be a quick solution for coming off the DC bat.circuit after the 12V DC charging rec/regulator, but a regulated power supply is always better, more stable and more protection as the charging rec/regulator voltgage range is 14.1~14.9V DC. :)

The 03/04 wr's have a 12V rectifier regulator to charge the bat. If you put a 1/2A fuse in the wire coming form the magneto it will blow even from the current draw from the lights. You want to put the 1/2A fuse in line with the GPS circuit only.

  • pedman

Posted January 07, 2004 - 10:32 AM

#23

:D :D :)

Buy Batteries!!!

If it cost to much I know where you can get NiCd or NiMh from 150mAh - 1300mAh for NiCd and 600mAh - 2000mAh for NiMh. You can recharge these too.

I hate to see anyone that does not have much electrical background destroy a $300 GPS for a few bucks of good rechargables :D

  • PBDBLUE

Posted January 07, 2004 - 10:40 AM

#24

I agree with you and that is the point I was trying to make earlier. You reminded me of another alternative for the Etrex that's pretty good (and safe). Cycoactive Battery Pack

  • GPS Dual Sport

Posted January 07, 2004 - 12:07 PM

#25

The main reason for external power connection on the Garmin GPS is to avoid the shutting off problem with hard hits.
The other reason for external power is running the backlight full time. This is not a big deal until you're caught riding after dark. Garmin GPS models will shut the backlight off after a preset time unless you're running external power.

  • pedman

Posted January 07, 2004 - 02:23 PM

#26

The main reason for external power connection on the Garmin GPS is to avoid the shutting off problem with hard hits.
The other reason for external power is running the backlight full time. This is not a big deal until you're caught riding after dark. Garmin GPS models will shut the backlight off after a preset time unless you're running external power.


Your probally right and thats why I have a Magellan :D You can leave the lights on and lock the keys. :)

  • Rich_in_Orlando

Posted January 07, 2004 - 06:48 PM

#27

I've had my share of problems with bike-mounted GPSs over the years and I've spent a lot of money replacing stuff-I'm on my 7th GPS since 1999- so I've learned this the hard way. I'm going to tell you the easiest and safest way to externally power your GPS on your bike. This will be a total loss system but will be completely isolated from the bike's electrical system. This is for safety because if your voltage regulator goes out on you (I'm on my 3rd on this bike) the GPS will not be fried. (I killed a Garmin GPS III+ last year when my last regulator died.)

You'll need to get a 12V 1.3 ah sealed lead acid battery and a good battery charger. Batteries Plus sells the batteries for less than 20 bucks. I use a Battery Tender Junior battery charger and they are good for lots of things besides this. All you have to do is find a place to store the battery on the bike then connect it to the GPS. I mounted mine above the headlight with zip ties. The battery will power the GPS for at least a week of continuous use before it needs recharging. How do I know that? I keep the battery charged up before each ride but on my last 2-day camping trip, I rode for about 15 hours total. When I got back home it took literally 30 seconds for the charger to top off the battery. A fully discharged battery takes about an hour to recharge. It hadn't made a dent in it.

Here's a picture of how my battery is mounted. As you can see, the leads coming off the battery are connected to the GPS power cable with one of those 2-pole connectors. That's where I plug the Battery Tender in to charge it.
Posted Image

Also, I use rubber vibration isolators to keep the GPS from vibrating to death. The 5 other GPSs died from vibration before I wised up. Here's a picture of my home-made mounting system:
Posted Image

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  • Gadsen

Posted January 07, 2004 - 08:17 PM

#28

Hey, this post has really taken off! :D Now I DID say to use a regulator. I did not say to just to rectifiy it. The diagram was only for the rectifier (AC to DC conversion part) and a regulator from Dennis Kirk or something like what the other poster said from Radio Shack is a must. Also, a small 12V battery pack would work in place of a capacitor and allow the GPS to run with the engine off (stopped for a rest) a rechargeable battery to boot! This thread is getting to be fun! I'm enjoying all this cool input. I see i'm not the only "McGuyver" here! :)

  • PBDBLUE

Posted January 07, 2004 - 08:36 PM

#29

It has been a good discussion with a lot of input from many. I think a lot of good info came out of this.

  • 5spoke

Posted January 07, 2004 - 09:26 PM

#30

Hey toyota_mdt_tech

Thanks for shipping the insert. I'm going to do some mods on it and compare it the the one I have. It should be fun having 2 so I can switch them quickly and hopefully campare noise and performance.
Cheers

  • Tom14911

Posted January 09, 2004 - 10:56 AM

#31

I'm gonna go with the big rechargeable battery. I already have a tender and the two pole connecting device for the tender.

It seems the easiest, quickest and safest....for me.

Thanks for all the great input.

Tom

  • Gadsen

Posted January 09, 2004 - 08:19 PM

#32

I'm gonna go with the big rechargeable battery. I already have a tender and the two pole connecting device for the tender.

It seems the easiest, quickest and safest....for me.

Thanks for all the great input.

Tom



Tom, you candyass! :) Not a bad idea though. But if you get to feeling cocky again, you could build this system and have it charge the battery you install. With the battery in place, you wouldnt even need a capacitor, the battery itself will act as a cushion for spikes. :D Turned out to be a very interesting thread with all the neat input I though, and educational too. Maybe see ya on the trails sometime. :D

  • Dan_Lorenze

Posted January 10, 2004 - 05:41 AM

#33

Your GPS will get very angry with the polarity reversing 50% of the time.



Dan, you still got it.... :) :D

Dan :D

  • 5spoke

Posted January 10, 2004 - 11:46 AM

#34

I'm running all my extra elec. stuff off of the existing/starter bat. on my bike, just like you would in any other vehicle.

Obviously you have to figure out how much power will be consumed, so as not to get a situation where the bat. doesn't get charged. Since we are talking about small amounts of power usage there shouldn't be a problem. I have also added a on/off sw. for the lights to increase charging power when I think I'd need it.




 
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