External Power Supply Size

I am looking to power a spark core v1.0 with an AC/DC converter that has a 5VDC output voltage and 400 mA max output current. I am only using one output pin drawing a max of 10 mA.

I read on (http://docs.spark.io/hardware/) the max current consumption of the core is 300 mA. However in the troubleshooting section (under flashing green) it is noted that a power supply should be able to supply 500 mA and the recommended size of the power supply is 5VDC @ 1A. Can someone clear up this up for me?

The WiFi module can draw oddly large amounts of power for very brief amounts of time. The suggestions are there to ensure that you have plenty of power available for the Core. I imagine the larger numbers are there in a desire to “play it safe” since many power supplies provide less then they are rated for in practice.

That being said, you will probably be find with your 400ma supply. I would suggest you put some fairly high capacity caps across your input to ensure that you don’t brown out your spark device

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Thanks, that is what I suspected. I was looking to use the 400 mA board mount power supply due to the lack of space on the spark breadboard (larger power supply output current = larger footprint). After looking around online I found a 800 mA external power supply with wired connections which should alleviate both concerns (space on board and capacity of power supply).

If you’re only using 1 pin and your wifi isn’t moving a whole lot of traffic, you can probably get away with a very low current 3V3 supply (if that is an option for whatever is connected to that 1 pin) connected to the 3V3 pin, and a 1000uf capacitor between GND and 3V3 to provide current during wifi transmit periods.

It will require testing to be sure.

I’ve have really good luck with my portable Anker power charger. I joke that the Anker can jump start a car. This external battery auto-negotiates how much power the connected device needs. I use it with my other portable microcomputers such as the Raspberry Pi and the Beagle Bone Black. When I plug and unplug things from the running device, there is a change in power requirements. The Anker detects these changes and reacts accordingly so I don’t fry or under power the device. Mine is rated at 13000mAh and has two USB outputs to power two devices at the same time.
I can easily get 9 days of continuous use out of the Anker using the RPi B+, a touch screen, a WiFi dongle, a Bluetooth keyboard and a USB thumbdrive. I am quite sure the Anker 79AN7925 will do what you want it to do for power and potability.

Hi, @harrisonhjones I know this post was sometime back so forgive me :grimacing: But you said

How does high capacity caps prevent the spark from browning out? If the power source is out of power wouldnt the spark still brown out regardless of whether you have the caps or not? Thanks! Sorry if its common sense I’m still new to these electronics things.

Well, I was being very cautious.

Let’s assume for a second that the core, for a very brief period of time when it was just turning on the WiFI module needed 500ma of power. That 500ma is greater than the max amount of current your voltage regulator/converter is capable of providing. When it attempts to the voltage will drop. If the voltage drops below a certain point the CC3000 and the Core itself will “brown out” and die. Once it dies the current consumption will drop and the core will again try to turn back on. Repeat!

So, by adding some capacitors between the voltage regulator and the spark core’s inputs (in parallel with the voltage regulator’s output and the core’s input) you can essentially store up enough charge to “survive” these brownout attempts. Caps can’t (normally) store a lot of power but the power they do store can be accessed very quickly (high amperage). Which is what you want

Oh I see! So it’s sort of like a really short emergency supply. So roughly how high is the high you’re referring to for the value of the capacitors?