power supply from battery and car outlet

[[email protected]]

I am working on a GPS data logger working on 3.3V
I'm pretty much done with all the digital design but one thing is still
missing and I'm not familiar enough with analog electronics to do it.
I would like the device to be able to get power supply from both 3-4 AA
batteries and from a car outlet supply. when the car supply is
connected, the batteries are not wasted, and when its not, the
batteries automatically switch in.
does anyone have a schematic of a circuit that does this for me to
follow? or can anyone explain how to do it?
thank.
Shy

 

[Michael A. Terrell]

I am working on a GPS data logger working on 3.3V
I'm pretty much done with all the digital design but one thing is still
missing and I'm not familiar enough with analog electronics to do it.
I would like the device to be able to get power supply from both 3-4 AA
batteries and from a car outlet supply. when the car supply is
connected, the batteries are not wasted, and when its not, the
batteries automatically switch in.
does anyone have a schematic of a circuit that does this for me to
follow? or can anyone explain how to do it?
thank.
Shy

If you use a pair of current steering diodes, the one with the higher
voltage will power your unit. In other words, the diode from the
battery will be reverse biased, and will turn off the current flow from
the battery. It will also prevent the battery being damaged by a
reverse current.

 

[Rich Grise]

I am working on a GPS data logger working on 3.3V
I'm pretty much done with all the digital design but one thing is still
missing and I'm not familiar enough with analog electronics to do it.
I would like the device to be able to get power supply from both 3-4 AA
batteries and from a car outlet supply. when the car supply is
connected, the batteries are not wasted, and when its not, the
batteries automatically switch in.
does anyone have a schematic of a circuit that does this for me to
follow? or can anyone explain how to do it?
thank.

You get a regulated adapter like a RS one, that provides, say,
6V from the car jack.
http://www.radioshack.com/search.asp?find=car+dc+adapter&site=search&image1.x=0&image1.y=0&SRC=1
(mind word wrap)
Then get a connector like, for example, one of figure 17 - 31 here:
http://dkc3.digikey.com/PDF/T053/0286.pdf .

These are called, I think, "shorting jacke", but someone will correct
me if I'm in error on that. The battery goes to the NC contact, and the
movable contact goes to the circuit. The center conductor is common to
both.

Have Fun!

 

[[email protected]]

yes exactly shooshx u can use diode as switches to make ur work more
reliable