How to power my GPS receiver

[brodin]

I have a Superstar GPS module receiver. It needs a 5V supply, I usually takes that from the USB port because i have a USB-RS232 converter (which leaves 5V output also).

But now I want to power the receiver by an external source to be able to connect the module directly to the COM port on my older computer which has no USB port.

I have batterypackages marked 6V (fully charged they reach almost 7 V). How do i get 5V from that battery. I can't use a 7805 regulator because Vin are to near Vout. How could i solve this?

 

[evandude]

you can buy low-dropout regulators (LDO) that allow you to have a very small difference between Vin and Vout, sometimes as low as 0.5v or less (especially at low currents)

you can get power from the serial port, however usually only 5-10 mA and I seriously doubt that a GPS receiver would run on that little current.

if you wanted to get really fancy, maybe you could find a DC-DC converter. I know you can get 12v converters on ebay, designed to go into cigarette lighter sockets in cars, that are small and relatively cheap, that output various voltages (including 5v) so if you used two battery packs in series to get 12v or more then that would work... however the batteries and converter together would be larger than the GPS receiver...

of course you could also just use a small 5v wallwart power supply... but it's all going to depend on how much space you have.

 

[brodin]

to get really fancy, maybe you could find a DC-DC converter

Then i could just use a 7805 voltage regulator, but it feels bad to burn (12v-5v) * 200mA = 1.4 W to heat when the GPS draws 1W itself.
It would feel much better to use only one 6V battery.

An LDO may work then, depends on how much voltage it sinks at 200mA, may be worth checking up!

 

[evandude]

you can get LDO's that drop 0.5v at 1 amp.

and as for the DC-DC, well the whole point of using a DC-DC over a linear regulator is that it doesn't dissipate power like one. 80%, 90%, or even higher efficiency can be achieved so you don't waste power. But if you can get away with an LDO and only spend $1 on it, then go for it.

 

[brodin]

I bought a LDO at glitchbuster.com.

Thanks for the tip evandude!