Operating a BT receiver without the battery

Roy33 · 07-08-2008, 06:06 PM

Is it possible to operate a Bluetooth GPS Receiver (e.g. BT-Q818) using a USB/Power cable without the use of an internal battery. Currently if the battery is removed the unit will not power up even if connected to the mains.

Would like to have the unit operate (on/off) only when an external power-source is available e.g. when hooked up to the car this will allow me to start/stop the GPS unit by turning the car's ignition switch.

nb. i know some GPS units have auto on/off, functionality but id rather save some money by modifying my existing unit, disassembled pictures attached:

Roy33 · 07-09-2008, 11:47 AM

Would connecting the (+) and (-) do the trick?

Tidder · 07-09-2008, 11:51 AM

Not unless you have a 3.7v power source to hook to the (+) and (-). USB is 5v. Computers do have a 3.3v typically, but for simplicity's sake, why not just leave the battery?

Roy33 · 07-09-2008, 12:09 PM

If i leave the battery it will charge as i drive and keep the GPS receiver active for 12+ hours after i switch off the car.. so will continue to broadcast Bluetooth..

and i don’t think its possible to stop the battery from charging...

phuz · 07-09-2008, 12:19 PM

I would just build a regulated 3.7v power supply and nix the battery.

nst6563 · 07-09-2008, 12:19 PM

I was faced with a similar issue as I have a globaltop g33 which has auto-off but not auto-on. I made a simple circuit using a relay, a couple diodes, resistor, led's and some capacitors. When the computer turns on, it flips the relay and turns on the BT gps receiver, when the computer turns on, the caps drain and flip the relay again and turn it off. USB cable plugged into the usb port for charging the battery when computer is running and the relay is connected to the on/off switch of the gps receiver.

I found the schematics on this site, but don't have time to search right now. If I get a chance later I'll do some searching as it would be your best option. That way you can have a 'warm' start for gps signal aquisition while not worrying about it staying on or not turning on.

Tidder · 07-09-2008, 12:38 PM

Or could simplify even more by just using a relay hooked to the usb 5v and in between the battery and device on the positive lead.

skuller · 07-09-2008, 04:37 PM

Quote: Originally Posted by nst6563

I was faced with a similar issue as I have a globaltop g33 which has auto-off but not auto-on. I made a simple circuit using a relay, a couple diodes, resistor, led's and some capacitors. When the computer turns on, it flips the relay and turns on the BT gps receiver, when the computer turns on, the caps drain and flip the relay again and turn it off. USB cable plugged into the usb port for charging the battery when computer is running and the relay is connected to the on/off switch of the gps receiver.

I found the schematics on this site, but don't have time to search right now. If I get a chance later I'll do some searching as it would be your best option. That way you can have a 'warm' start for gps signal aquisition while not worrying about it staying on or not turning on.

I would also be interested with the scheme.
I tried to search but can't find one.

JimmyFitz · 07-09-2008, 11:27 PM

My first carPC implementation had a Royaltek RBT3000 GPS unit. It was similar in that it had its own battery with a charger and it had a hardwired on/off switch. I installed it in the trunk and connected its charger to constant 12V. The current draw from this device was minimal and even less, once the battery got fully charged. Yes, the Bluetoooth radio was always on, which would allow someone to "Bluejack" my GPS. What would it tell them other than give a current location of the car, which they already know anyway because they must be within 30' to connect. I later changed to a BU-353 to get newer technology SiRF.

Badgerboy · 07-10-2008, 03:29 AM

I had this problem with my Dell Bluetooth reciever. If I left the unit on however, it got very upset and would randomly turn off.

In the end I just disconnected the battery, and it worked fine. The only problem is the unit is an older one and has a rubbish cold start time. Matter of fact the unit has become a bit of a liability. (Likes to track down the wrong roads these days and excels at getting me lost)

I was looking at a new USB device, as my understanding was that they would only pull power from the the CarPC negating this issue. Does anyone know of a good unit, (Ideally Sirf Star 3 chipset), with the standard jack for my external GPS antennae?

nst6563 · 07-10-2008, 10:04 AM

Found the post where I got my circuit from.
http://www.mp3car.com/vbulletin/249253-post9.html

It's basically a combination of the Delay On and Delay Off.

I'll have to take the carpc apart this week/end so I'll pull the circuit out and draw up a diagram as best I can. I'll take a picture as well. But be warned, it's a mess but it works great