hacking belkin serial/usb adapter to power etrex

Yannick Tamer · 05-14-2004

Hello,
I hope this was not covered before in this forum. I did search and found nothing about hacking it. Sorry if I missed it.

I'm talking about this belkin adapter and hacking it this way (the first method using diodes).

Has anybody tried connecting the 5V from the USB to the pin 8 on the serial port with diodes, on this particular adapter?

I'm a bit scared of frying my laptop or my etrex or the adapter. I know I cannot use the adapter for anything else than my GPS after that, but that is ok. What other devices uses the serial port lately anyway!

btw, this adapter works great so far.

Thanks

Eyecannon · 05-14-2004

Pretty interesting... I might have to try this with mine (or get a spare one off ebay for $10).

lincomatic · 05-14-2004

why do you want to hook it up to the serial adapter? does the power pin on your etrex cable connect to that? i don't think it's a good ideal to connect the 5V USB power line to that. it's safer to separate it. hack your etrex cable instead to isolate the pin 8 from the serial adapter and then hook the power & diodes to the etrex side of the cut.

i built my own cable using an etrex connector from pfranc.com and then hooked it to a 5V ipaq cigarette lighter charger via about 4 series diodes (sorry i don't remember the details because it was 3yrs ago, but it's always a good idea to measure the voltage under load and add diodes until you get as close to 3V as you can).

it appears from the link you sent that the guy hooked up the zener diode in series. that's not the right way to do it. zeners are supposed to be hooked up as a shunt. here is a link to the proper circuit...page down to "Voltage Shunt Regulator."

http://www.itee.uq.edu.au/~engg1030/...age/lect10.pdf

personally i like the series diode idea better because it doesn't waste power thru the shunt and load down the USB output needlessly (less chance of frying yr laptop). the only problem w/ the series diode circuit is the voltage fluctuates a bit w/ different loads so it's impt to put enough diodes to get the loaded voltage down to 3V. if you don't have a voltmeter start w/ 6 diodes if the etrex is flaky remove them one by one until the etrex runs stably.

Yannick Tamer · 05-14-2004

>why do you want to hook it up to the serial adapter? does the power pin on your etrex cable connect to that?

Yes, I forgot to mention that I would hack my own cable with the etrex power connected to pin 8. (It could be any other pin that will not interfere with the serial adapter). Pin 8 seams to work ok for the usb adapter they sell on pfran.

Thanks for the suggestions.

I don't get what you mean by: page down to "Voltage Shunt Regulator."

lincomatic · 05-14-2004

Quote:

Originally Posted by Yannick Tamer

>why do you want to hook it up to the serial adapter? does the power pin on your etrex cable connect to that?

Yes, I forgot to mention that I would hack my own cable with the etrex power connected to pin 8. (It could be any other pin that will not interfere with the serial adapter). Pin 8 seams to work ok for the usb adapter they sell on pfran.

Thanks for the suggestions.

I don't get what you mean by: page down to "Voltage Shunt Regulator."

oops! sorry forgot to embed the link:

http://www.itee.uq.edu.au/~engg1030/...age/lect10.pdf

McHale · 05-14-2004

not to go a step backwards, but is there a cheap place to get a PDA to eTrex adapter or a link to make one easily?

-Mc

lincomatic · 05-14-2004

Quote:

Originally Posted by McHale

not to go a step backwards, but is there a cheap place to get a PDA to eTrex adapter or a link to make one easily?

-Mc

buy a connector from a pfranc. hack it onto a serial sync cable. that's what i did. you could also just wire it up to a DB-9 so you don't have to hack the sync cable.

but i gotta warn you...the etrex outputs NMEA @ only 1 sample every 2sec. useless for navigation but acceptable, i suppose, for stumbling.

McHale · 05-15-2004

oooh.. those things aren't cheap. Well, it came with a serial cable so I'm 1/2 way there. I suppose I could pick up a serial adapter for the iPAQ and just use a null modem.

The cheapest I've found for an iPAQ to eTrex is about 35 bucks on eBay. Not too bad a price compared to pfranc.

And as far as 1 sample for every 2 sec, other than stumbling, what else is GPS for?

thanks for the info...

-Mc

Barry · 05-15-2004

Hey McHale, if you have an iPaq 38xx to 55xx the cable I built will work with it. Used a spare etrex serial cable and a usb sync and charge cable I got at sears to build it.

Link

lincomatic · 05-15-2004

Quote:

Originally Posted by McHale

oooh.. those things aren't cheap. Well, it came with a serial cable so I'm 1/2 way there. I suppose I could pick up a serial adapter for the iPAQ and just use a null modem.

the e-plugs aren't too expensive actually...
http://www.pfranc.com/projects/g45contr/emap/index.htm
i paid $12 for two a few years ago...looks like they bumped up the recommended price $3. since you already have the serial sync cable all you need is a DB-9 female connector and any old cheap wire. since you'd be connecting up the DB-9 yourself you wouldn't even need a null modem. if you need help let me know and i'll dig up my old wiring diagrams.

McHale · 05-16-2004

I didn't see the eplug info. That's a pretty decent price. And 15 for 2 plus getting 2 iPAQ cables for about 5 a piece makes it less than 15 a piece! That's pretty cheap.

Barry, that page is exactly what I was looking for! Thanks!!!

-Mc

Barry · 05-16-2004

welcome!

05-14-2004	#1 (permalink)
Yannick Tamer Registered Member Join Date: Sep 2002 Posts: 2	hacking belkin serial/usb adapter to power etrex Hello, I hope this was not covered before in this forum. I did search and found nothing about hacking it. Sorry if I missed it. I'm talking about this belkin adapter and hacking it this way (the first method using diodes). Has anybody tried connecting the 5V from the USB to the pin 8 on the serial port with diodes, on this particular adapter? I'm a bit scared of frying my laptop or my etrex or the adapter. I know I cannot use the adapter for anything else than my GPS after that, but that is ok. What other devices uses the serial port lately anyway! btw, this adapter works great so far. Thanks __________________ Tamer

05-14-2004	#2 (permalink)
Eyecannon Ward River Join Date: Aug 2002 Location: Santa Monix Posts: 679	Pretty interesting... I might have to try this with mine (or get a spare one off ebay for $10). __________________ No, officer, YOU are under arrest! http://eyecannon.com/wardrive.html

05-14-2004	#3 (permalink)
lincomatic Squaaawk! WiFi! WiFi! Join Date: Apr 2002 Location: Tinsel Town Posts: 1,682	why do you want to hook it up to the serial adapter? does the power pin on your etrex cable connect to that? i don't think it's a good ideal to connect the 5V USB power line to that. it's safer to separate it. hack your etrex cable instead to isolate the pin 8 from the serial adapter and then hook the power & diodes to the etrex side of the cut. i built my own cable using an etrex connector from pfranc.com and then hooked it to a 5V ipaq cigarette lighter charger via about 4 series diodes (sorry i don't remember the details because it was 3yrs ago, but it's always a good idea to measure the voltage under load and add diodes until you get as close to 3V as you can). it appears from the link you sent that the guy hooked up the zener diode in series. that's not the right way to do it. zeners are supposed to be hooked up as a shunt. here is a link to the proper circuit...page down to "Voltage Shunt Regulator." http://www.itee.uq.edu.au/~engg1030/...age/lect10.pdf personally i like the series diode idea better because it doesn't waste power thru the shunt and load down the USB output needlessly (less chance of frying yr laptop). the only problem w/ the series diode circuit is the voltage fluctuates a bit w/ different loads so it's impt to put enough diodes to get the loaded voltage down to 3V. if you don't have a voltmeter start w/ 6 diodes if the etrex is flaky remove them one by one until the etrex runs stably. Last edited by lincomatic : 05-14-2004 at 01:22 PM.

05-14-2004	#4 (permalink)
Yannick Tamer Registered Member Join Date: Sep 2002 Posts: 2	>why do you want to hook it up to the serial adapter? does the power pin on your etrex cable connect to that? Yes, I forgot to mention that I would hack my own cable with the etrex power connected to pin 8. (It could be any other pin that will not interfere with the serial adapter). Pin 8 seams to work ok for the usb adapter they sell on pfran. Thanks for the suggestions. I don't get what you mean by: page down to "Voltage Shunt Regulator." __________________ Tamer

05-14-2004	#6 (permalink)
McHale approved for all ages... Join Date: Apr 2002 Location: BFE Illinois Posts: 262	not to go a step backwards, but is there a cheap place to get a PDA to eTrex adapter or a link to make one easily? -Mc __________________ "I am confident that if anything can out-suck Limp Bizkit today it will be Limp Bizkit tomorrow" -MC Hawking

05-15-2004	#8 (permalink)
McHale approved for all ages... Join Date: Apr 2002 Location: BFE Illinois Posts: 262	oooh.. those things aren't cheap. Well, it came with a serial cable so I'm 1/2 way there. I suppose I could pick up a serial adapter for the iPAQ and just use a null modem. The cheapest I've found for an iPAQ to eTrex is about 35 bucks on eBay. Not too bad a price compared to pfranc. And as far as 1 sample for every 2 sec, other than stumbling, what else is GPS for? thanks for the info... -Mc __________________ "I am confident that if anything can out-suck Limp Bizkit today it will be Limp Bizkit tomorrow" -MC Hawking

05-15-2004	#9 (permalink)
Barry Managing the iTards. Join Date: Dec 2002 Location: Ohio Posts: 5,973	Hey McHale, if you have an iPaq 38xx to 55xx the cable I built will work with it. Used a spare etrex serial cable and a usb sync and charge cable I got at sears to build it. Link __________________ Never do anything you don't want to explain to the paramedics.

05-16-2004	#11 (permalink)
McHale approved for all ages... Join Date: Apr 2002 Location: BFE Illinois Posts: 262	I didn't see the eplug info. That's a pretty decent price. And 15 for 2 plus getting 2 iPAQ cables for about 5 a piece makes it less than 15 a piece! That's pretty cheap. Barry, that page is exactly what I was looking for! Thanks!!! -Mc __________________ "I am confident that if anything can out-suck Limp Bizkit today it will be Limp Bizkit tomorrow" -MC Hawking

05-16-2004	#12 (permalink)
Barry Managing the iTards. Join Date: Dec 2002 Location: Ohio Posts: 5,973	welcome! __________________ Never do anything you don't want to explain to the paramedics.

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