BT GPS auto power on mod ? capacitor circuit ?

powerlord · 10-25-2005, 09:28 AM

I have a GRB-248 bluetooth GPS.. the one on ebay with the single button on/off.

Works fine, but I want to now mount it full time in the car with the 12v adapter... thing is.. it doesn't auto switch on power with 12v... so every time you go into car you have to turn it on.. which is a right pain. Even more now as I'd like to mount it somewhere where it is not visible.

I'm thinking, a capacitor and resistor through a replay to provide a close switch pulse for about 4 seconds.

Has anyone worked out cap/resistor values for this for something else (like lilliputs or whatever) ?

stu

powerlord · 10-25-2005, 03:24 PM

ok, if anyone is interested my circuit works.

I just tried the first 2 components I got out my spares bin.

1 500 uF capacitor in parallel with a 36K resistor across the switch.

so when switched on, switch is 'closed' by capacitor until it charges (couple of secs). though switch is still 'closed' after that by resistor its at a high enough impedence for the gps to think its open (keeping the switch down would cause it to switch off after 10 secs or else I'd have just shorted switch).

when power is off, capacitor discharges through resistor. After 30 secs if power returned, it powers on again. job done.

stu

gizak · 10-26-2005, 10:46 AM

coolness, I got a bluetooth GPS unit too and had the same annoyance. I'm too lazy and just hardwired it to the battery lol, so I commend you on your efforts. Although it is nice having a GPS lock instantly everytime I get in the car (except when I park underground!).

-oh yea, car battery has never died from this and I have gone 4-5 days without driving.