battery charging, how do i go about this.

hey guys , im getting ready to start my next project. my idea is to have a wooden cube with the standard 6 sides , one will be the base and the other 6 will have acrylic windows and each window will have an image on it , the cube will be fitted with tilt sensors and as the user tilts the cube each window will light up ( ill use either shiftbrights or megabrights) and so on , because the cube needs to be portable, i need it to run on a battery that can be recharged thats all easy enough so far , but the catch is , i need the cube to be able to be recharged on the fly so the battery needs to be able to be recharged without it being taken out of the cube , i was thinking a positive and negative metal plate ont he bottom , and the cube could be sat on a sort of cradle, and when its not being played with it can be sat on the dock and charge itself again , as i write this im thinking of the magsafe charger from apple, something like that , does anyone have any ideas? any help would be great. im nto so sure about how to do this , if its possible without being dangerous. thanks

Well if it's a cube, I would have the corners as metal contacts. Have something like 9-12V going into a base which the corners slot into so it looks like a diamond, one point hanging down. If you connect the opposite points up, one to ground and one to the voltage+ then you could put any two corners into the stand and it'd charge.

The reasson why I say 9-12V is then you could have a full-wave recifier circuit (4 diode square) which would allow it to charge whichever way round the contacts were (you then need more than 5V due to voltage drop in the diodes). Then stick a 5v regulator and a lipo charger inside the cube.

I think that's the coolest way to do it. Ask if you are unsure about anything I have said.

Sounds like a cool project though :slight_smile:

Mowcius

hey , thanks for your reply , im not sure on a few things , are you familiar with shiftbrites? if not heres a link to a basic rundown of them. Headerless ShiftBrite 2.0 - Macetech Electronics Store . i understand from what you said that on each corner of the cube id have a metal corner that would act as a contact , and to charge the cube id sit it on the dock ,( which would be square and have 2 contacts ) , any 2 of the 4 contacts can touch the dock in any order and it will charge the cube. on the inside there would be a circuit , this is where i am stuck , im really not so good with cimagining how electronics work , but im capable of assembling them with detailed instruction :slight_smile: , the shift brites need 7v roughly to power the aount i need , which would be around 25 to 30 , any help would be greatly apreciated you seem to know what your on about , its awesome. thanks ,

am i on the right track with this as the lippo charger SparkFun USB LiPoly Charger - Single Cell - PRT-12711 - SparkFun Electronics ? or is that too weak but im assuming thats the sort of thing you mean

ok so i have done a bit of research into the things you mentioned , and i think i understand it better now, the dock has 9-12v running from the wall to the 2 contacts on the dock. the cube has 4 contacts , and can be placedin any way into the dock , the 9-12v runs from the dock into the cube into the full-wave recifier circuit which converts the ac current into dc current , then the dc current flows out through a 5v regulator , and into the lippo charger which chargers the battery, and then in turn the battery powers the arduino and the shiftbrites

ok so i have done a bit of research into the things you mentioned , and i think i understand it better now, the dock has 9-12v running from the wall to the 2 contacts on the dock. the cube has 6 contacts , and can be placedin any way into the dock , the 9-12v runs from the dock into the cube into the full-wave recifier circuit which converts the ac or dc current (dc can be backwards then) into dc current (the right way round) , then the dc current flows out through a 5v regulator , and into the lippo charger which chargers the battery, and then in turn the battery powers the arduino and the shiftbrites

You've got it!

My electric toothbrush uses a simple coil in the base connected to the power mains. When you put the handle of the toothbrush into the base, it magnetically couples to a coil in the handle and transfers power magnetically to recharge the battery. Simple, elegant, and very safe.

Not easy to DIY though

with this as the lippo charger SparkFun USB LiPoly Charger - Single Cell - PRT-12711 - SparkFun Electronics ? or is that too weak but im assuming thats the sort of thing you mean

Yeah that sort of thing, might be ok if you stick in a small-ish capacity battery and minimise power usage for the electronics...

Mowcius

awesome , im getting the idea of it , say i just had a positive and a negative metal plate on the cube i could ditch the full wave rectifier ? , and just have say 7v dc coming in via wall wart , and straight into the lippo charger, into the battery then from the battery straight to the arduino, where could i find the right battery and lippo charger , cos i would need more than the 3,6v i found , id need around 7 , the specs of the shiftbrite say "Current: 60mA maximum (all channels on" dont litium batteries out out like 1000-2000? or am i getting this wrong. thanks

awesome , im getting the idea of it , say i just had a positive and a negative metal plate on the cube i could ditch the full wave rectifier ?

Well if you were sure people were only going to put it on the contacts the right way round. You could just stick in a diode to stop it working the wrong way round but you might as well use 3 more and make it work either way round...

, and just have say 7v dc coming in via wall wart , and straight into the lippo charger, into the battery then from the battery straight to the arduino,

The diodes drop the voltage slightly so it would not be quite 7v by it got to the charger but that would be ok.

Where could i find the right battery and lippo charger , cos i would need more than the 3,6v i found , id need around 7

Most lipo chargers are at 3.6-3.7v as that is the voltage of a lithium ion cell. You will need a step-up converter after that to get it to 5v for the arduino (and shiftbrites)

the specs of the shiftbrite say "Current: 60mA maximum (all channels on" dont litium batteries out out like 1000-2000? or am i getting this wrong.

yes, sparkfun sell them from 20mAh to 6000mAh. Once you have stepped up the voltage then this will decrease slightly at the new voltage.

Mowcius

ooooh , i just stumbled across something , http://www.liquidware.com/shop/show/BP/Lithium+BackPack its a battery pack for the arduino, this could solve all my problems, what are your thoughts on this ? would it provide enough juice for me? and it also includes the charging circuit so i could just modify the usb mini connector , to a more dock like connector such as pins or somehting