i want to do something like arfuino UNO this but it says i need to connect 5V and ground to make it power, the spark has a ground but doesnt have 5V. the docs says VIN powers up 3V-6V. Where can i connect 5V with the spark core?
When it states 3.6V-6.0V this does include 5V (3.6 < 5.0 < 6.0) 
Just supply 5V to Vin and you are good. There is a voltage regulator, that does the down shifting to 3.3V
But all the outputs will be 3.3V, so you might have to adjust your resistors (for LED current) accordingly.
Or … you get a Shield shield, then you have 5V on the outs, too.
I could be mistaken, but I believe the V_in pin is capable of providing 5V.
i have another question regarding to V_IN to 5V, why is it that when i’m connecting my gps receiver which need to be supplied by 5V and GND it doesnt work? even if it initialises for several hours?
Actually it’s not providing 5V - it can take 3.6V to 6.0V - but if you power your Core via USB (5V) you can take the 5V USB power for other components off the Vin pin, too - just be aware of the current limitations connected with your source (e.g. max. 500mA if connected to a USB 2.0 port)
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To answer this question, you'd need to provide some more background info.
How do you power the Core? What current can your source provide?
Have you got "free" reception of GPS satellite signal? Inside your home the signal might not be good enough.
What exactly does not work? Does it not power up? Does it not sync? Does it not send NMEA sentences? Are sentences corrupred? ...
the core is connected via usb to my laptop. the whole GPS is not working, i have waited for several hours it really doesnt show a red light (blinking) which signifies it up and running. no furthur steps had taken because it needs to be connected first which is a problem.
the gps has 6 pins:
- GND
-VIN
-RX
-TX
-GND
-IPPS
the GPS needs 5v stated in its datasheet.
I think the problem might be related to the power output of the Core. According to the GPS datasheet:
Power Consumption
44mA (Continuous Mode)
25mA (Trickle Power Mode)
The Core however can only supply up to 20mA per I/O pin (as far as I'm aware). Since this is lower than the minimum requirement, it could/should give problems. You might try to power the GPS unit externally, which could help. If you're desperate for a power supply; I've been using a broken USB cable for three months, with the two power cables plugged into a breadboard, which works fine.
im using a GlobalSat EM406-A gps module. right now as scruffR said, i can connect RX/TX of the GPS to the D0/D1 of the spark. still no sign of running. i’m connecting it right now to my power outlet.
i dont understand “I’ve been using a broken USB cable for three months, with the two power cables plugged into a breadboard, which works fine.”?
What I was trying to say was that the Core itself isn’t able to power the GPS unit. Although it’s hooked up to the wall, the maximum amount of current that can go through one I/O pin is 20mA (as per the docs). If you’re hooking up something that requires 25mA to run, then it won’t work. You can power the GPS unit externally by connecting it to a power supply that isn’t running through the Core. That means that you’ll have to provide 5V which you can connect the GPS to, whereas the data lines will still go to the Core.
The whole “broken USB cable” was meant as an alternative in case you don’t have a 5V supply laying around (which I didn’t). This way you could use the 5V coming out of a computer/wall adapter to power your GPS. If you do have a decent power supply then, by all means, please use that instead!
Sorry to contradict, but while it is true, that the GPIOs only drive about 20mA this is not true for Vin which - in @paolosofio01 's case - does supply the power for the GPS module.
The current that can be drawn from Vin depends on the power the USB source is able to drive (for some wall warts 2000mA - which would maybe produce lot of heat on the Core’s USB->Vin trace ;-)), it has nothing to do with the Core’s GPIOs.
In that case I’ll take back my words, and the problem probably lies elsewhere. Still shouldn’t hurt to power your electronics externally. This might be useful to be added to the docs though, since I’ve gone through them a couple of times, and haven’t yet found the limit of the V_in.
I agree - this could be documented better.
The docs are even somewhat missleading (Getting Started - Pins)
VIN: Connect an unregulated power source here with a voltage between 3.6V and 6V to power the Core. If you're powering the Core over USB, this pin should not be used.
This should mean don’t supply current into Vin, when connected via USB, but drawing current from USB via this pin is perfectly legal
There are some posts on this forum tho’, which suggest this use of Vin - maybe I’ll find some
And maybe I’ll find time and the right words to put it into docs - they are open source after all.
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1.) Power up your core via USB
2.) Wire up Vin of core to Vin of GPS
3.) Wire up Gnd of core to Gnd of GPS
With regards to the red light, I’m not sure if there should be light the moment you power up or something.
Make sure you connect the wires correctly or risk damaging the GPS unit.
Can i use a non-lipo battery for the battery shield to power up the core and the gps?
Which battery are you looking at?
I would not recommend doing so as the charging circuit is designed for Lipo batteries and if you use other chemistry of batteries, that might result in some undesirable effect and lead to safety issues.
i need a larger amount of power supply to support the power needed by the gps which is 5V.
Please read the docs: http://docs.spark.io/shields/#battery-shield
There is a built in boost converter to bring up the voltage to 5V for the core.
@kennethlimcp, @ScruffR, @paolosofio01 and @Moors7, I just wanted to point out that Vin (also known as RAW on the Core schematics) on the Core serves two purposes. The first is to power the Core from an alternate (from USB) power source, typically from a battery, with a voltage range of 3.6 to 6V. This is fed directly to the onboard 3.3V regulator which can provide a maximum of 500ma at 3.3V.
The second is to route USB power to a user’s circuit. The USB power is routed to the Vin pin via a protection diode which has a small voltage drop, resulting in a Vin voltage of about 4.7V. Furthermore, that diode is rated for a maximum of 500ma of current. For lager currents, the Core and user circuit should be powered in parallel or from separate power supplies (with common grounds). 
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