Powering a GPS module by a battery?

Thread Starter

MobiTech

Joined Aug 24, 2018
11
Some batteries are hard to tin on their metal surfaces, in order to solder on wires, often needs a big iron and flux.
Possibly damaging the battery.

Look here,
https://www.ebay.co.uk/sch/i.html?_...holders.TRS0&_nkw=AA+battery+holders&_sacat=0
Does it mean that there is a security risk if I solder the Red cable to vcc pin, the black cable to gnd pin and then input 4 AA batteries to the battery holder? Are you talking about damaging the battery or the battery holder?
 

ericgibbs

Joined Jan 29, 2010
18,766
Hi,
I did not mention the GPS VCC or GND pin , in post #20.?
Earlier you where considering soldering batteries rather than using a battery pack, thats why I posted the cautionary note about soldering to batteries.

E
 

ericgibbs

Joined Jan 29, 2010
18,766
Buy a 4*AA battery holder with flying leads, Red/Black.
Solder the Black wire to the GPS module GND pad. The Red wire to the GPS module VCC pad.
Insert the 4 batteries into the holder after soldering the above wires.

You could also buy a 4*battery holder with a On/Off switch already fitted.
 

Thread Starter

MobiTech

Joined Aug 24, 2018
11
Buy a 4*AA battery holder with flying leads, Red/Black.
Solder the Black wire to the GPS module GND pad. The Red wire to the GPS module VCC pad.
Insert the 4 batteries into the holder after soldering the above wires.

You could also buy a 4*battery holder with a On/Off switch already fitted.
Great, thank you so much. I will give it a try. And 6V are not too much for a 3,3V reg?
 

ebp

Joined Feb 8, 2018
2,332
It may be wise to put a current limiting resistor in series with each of the Tx and Rx connections between the GPS module and the puck.

When two separately-powered devices are connected directly, there is a possibility that if either is unpowered the one that is powered will source excessive current into the input(s) of the other via input protection diodes. This is not destructive, provided that the current is limited to a sufficiently low level. Most datasheets now show a specification for this, but some don't (e.g. processors used in Arduino are poorly spec'd). Absolute maximum current is typically in the range of 5 to 20 mA, but I have seen spec's as low as 2 mA. In the absence of a specification, I would limit the current to no more than about 500 µA. With 3.3 V power supplies, this would require a resistor of 6.6k, but due to the voltage drop of the protection diode 4.7k, a common popular value, should be OK.

One drawback of using a series resistor is that it slows the signal transitions slightly at the receiving end due tot he capacitance of the input, however because async serial data rate is low this would not cause problems. It does require that the receiving end not have passive pull-up or pull-down resistors which would result in attenuation of the signal, probably causing bad HIGH or LOW voltage level.

This ap note from NXP deals with this topic specifically for their automotive microcprocessors, but covers the general issues well:
https://www.nxp.com/docs/en/application-note/AN4731.pdf
 

Thread Starter

MobiTech

Joined Aug 24, 2018
11
hi,
If I was using AA alkaline batteries, I would use a 4 * AA battery holder, giving 6v when the batteries are new.
They could be changed when then they have reached say 0.9v/battery, ie 3.6V.

Is there a reason for preferring to use batteries for the NEO module, also what is the module data output driving.?

E
View attachment 158724
Are 6V not higher than the maximum input voltage or is this no problem?
 
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