# Basic questions

First off I am still trying to learn all I can and know I by no means have a solid grasp on things. What I want to do with it is to be able to plug a 2s or 3s(one application takes a 2s the other a 3s) lipo battery into an arduino. With the battery powering it, I want to have it power 2 other boards that both need a 5v connection and also power one board that is 3v. That is all that the arduino has to do with those boards is send the proper voltage to them. I also want to add a buzzer that will beep when the lipo gets to its lowest safe level. I think this is all possible with the arduino though I am not sure about the supplying power part. Is there anyone would could take the time to tell me for the supplying power part what tutorials and things to read could you suggest so i can try and figure out how to achieve this. Would it be similar to supplying power to say a motor? Like you see in the motor tutorials? Also my other question is how does one decide what size resistors or diodes and things like that are needed for a project in general?

Thanks for any help with this

It depends on what you're doing. Most of all parts have some data sheet. Schematics are useful inside these :). As far as resistors go and diode or caps it all depends but I've used 22pf, 10uf, 100uf caps. Resistors has been 220 ohm, 10k ohm. Diodes have been 1n4001 (I like these :;) ).

With the battery powering it, I want to have it power 2 other boards that both need a 5v connection and also power one board that is 3v.

It all depends on how much current the three boards require. The 3.3vdc voltage pin is very limited on how much current it can supply, around 50ma I belive. The 5volt pin current capacity of the Arduino is better at around 700-800ma. You could always connect an external 3.3vdc regulator if you require more current for that voltage. So research the current requirements for those external boards and get back to us.

Lefty

Thanks for the responses so far. Sorry I did not think to post the specs on what I want to power. I also could be going about this wrong but it was the best idea I could come up with the be able to have something monitoring the battery life and power the other 2 boards easily.

Board one: gumstix summit expansion. ( I eventually want to have the arduino send a low batt warning to the summit/overo by i2c which I already have it doing with a different arduino ) http://www.gumstix.com/store/catalog/product_info.php?products_id=215&show_tab=details its a normal plug for a wall wart adapter with these specs rating: 16v DC @2.5A Contact resistance 30m OHMS MAX insulations resistance 50m OHMS MIN 500v DC voltage withstand 500V AC RMS for 1 minute life 5,000 cycles

The board itself has a 5v 50mA regulator and a 17V 1.5A synchronous step down converter

The second is: Macally powered 4 port USB hub http://www.bhphotovideo.com/c/product/551641-REG/Macally_TRIHUB4_TriHub_4_Port_Hi_Speed_USB.html the only info I can find on that one is that the AC adapter specs DC output 5V 2A positive in center

As far as the 3V part goes we can just scratch that as it was just me planning for the future and had some thoughts on things to add that were requiring a 3v source. So this is not really as important that I figure out now as I can come back later.

Please let me know any other info I can provide as I am happy to do any work to make it easier for the help from everyone. Thanks again and for taking the time :)

Where those not the correct current requirements? What other info can I post to help?

Thanks

Where those not the correct current requirements? What other info can I post to help?

Not specifically, it shows what the current capacity of the power modules that power the module boards, but not the actual current the boards consume. That aside, I think it's pretty safe to assume that you cannot use the Arduino's +5vdc and +3.3vdc to power those boards directly. You will rather have to utilize new external voltage regulators (one +5, one +3,3), driven directly from the Li-po battery (2C or 3C) which can then directly power the modules. Being that battery duration is almost always an issue, you would most likely want to utilize higher efficiency switching regulators rather then standard linear regulators.

Lefty

So then I would just be best to go with something like this http://www.sparkfun.com/commerce/product_info.php?products_id=114 and then just test battery life as to get a ball park of long the 2s and 3s would last?

Could I perhaps use those to power each board the put a arduino mini to monitor bat volatge for that power supply?

So then I would just be best to go with something like this http://www.sparkfun.com/commerce/product_info.php?products_id=114 and then just test battery life as to get a ball park of long the 2s and 3s would last?

Again you don't have complete required current specification yet, so it's impossible to calculate battery duration. Also the link you show uses a regulator rated as 1.5 amps max, actually less as there is no heat sink on that regulator. One of your modules you stated uses a wall wart rated at 2.5 amps, so that does not look like a solution.

Because you don't have the actual current consumption required by the modules you can only go by the maximum rated current of the wall wart modules you listed to try and size the required external regulators.

Bottom line, incomplete data can only lead to incomplete solutions or recommendations, sorry.

Lefty

Sorry for the misunderstanding I will go back and investigate further. I just did not think it would be as difficult since each board I will be powering will be getting there power from the lipo's through the existing plug that is designed for a wall wart, so I figured if I just supplied 5v to them they would be fine as they have the step down converters on the board. But i guess that logic was way off. THanks again and I will post back once I figure out the proper info.

I just did not think it would be as difficult since each board I will be powering will be getting there power from the lipo's through the existing plug that is designed for a wall wart, so I figured if I just supplied 5v to them they would be fine as they have the step down converters on the board.

Well possibly I misunderstood or misread your needs. A drawing might be useful, but power requirements is product of both voltage and current. You stated the voltage requirements pretty clear, but the current requirements were a little unclear to me, other then the ratings of the wall warts you provided which added up to much higher then an Arduino can provide or of the external regulator you linked to.

Lefty