Is this safe? 19V at 2amps over tinfoil paper? - Page 1
Forum section: electronics / beginners

author: eevfan007
author_rank: Contributor
timestamp: October 11, 2014, 03:55:05 pm
content: Hi!I'm building a virtual precense device:It's based on a roomba vacuum cleaner. And at the top is a cheap laptop.I want to charge the laptop when the droid docks. So I created this "connection":The charger for my laptop says 19V @ 2amps. So my question is, is it "ok" to have that charge go through this tin foil "connector" ?It would be ideal , since it would press fit onto my wall, when the droid goes in for a dock.Im a beginner in electronics, so I don't really know how to determine if this is safe.Thanks

author: Simon
author_rank: Unknown
timestamp: October 11, 2014, 04:00:30 pm
content: The voltage is fairly safe, my concern would be can you pass 2A through that foil, you need to measure the resistance and work out how much heat it could make. Can't you use a proper connector ?

author: SeanB
author_rank: Super Contributor
timestamp: October 11, 2014, 05:42:14 pm
content: I would be very careful trying to pass 2A through kitchen foil and cardboard toilet rolls, you will get a lot of arcing and poor connection. Better would be to get a connector that has large brass plates that have a light spring naturally, and have a matching plate to butt against. Provided you either gold plate them or clean weekly that will be a lot better.

author: Kjelt
author_rank: Super Contributor
timestamp: October 11, 2014, 06:42:14 pm
content: That foil is way to thin. Use a proper copper plate.No matter what connector you use you would like to detect that there is a decent connection before switching on and off the current.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 11, 2014, 07:41:10 pm
content: The foil would probably take 2A with a decent contact area.However, foil is rather brittle and won't take many "matings" with those toilet-paper tube "springs" behind them.The foil will start to crack and that will cause the contact area to arc and burn, and will deteriorate the whole scheme after a few cycles.It is possible that it is even a fire-hazard with flammable "springs" made of cardboard.IMHO, not recommended. Practically guaranteed to suffer an early failure, hopefully not catastrophic.

author: kolbep
author_rank: Frequent Contributor
timestamp: October 11, 2014, 08:37:00 pm
content: Inductive coupled charging may be better?

author: lgbeno
author_rank: Frequent Contributor
timestamp: October 11, 2014, 10:41:54 pm
content: Search digikey for EMI copper fingers and use this to replace the tin foil thing. Use some kind of sheet of metal on the wall to mate. I think this will help to resistance problem and the mating cycle problem

author: johansen
author_rank: Super Contributor
timestamp: October 11, 2014, 10:55:57 pm
content: 0000 steel wool.no, just kidding. don't do that.use copper sheet metal.or bronze wool (household magnetrons have a bronze wool washer in them)or a wad of copper wire wound up into a ball or something.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 11, 2014, 11:01:19 pm
content: You can find sheet copper or brass "flashing" materials for roofing at better hardware shops.You can find Beryllium Copper RFI/EMI Contacts gasket strips on Ebay.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 12, 2014, 02:40:21 am
content: Quote from: Richard Crowley on October 11, 2014, 11:01:19 pm^^^Tin plated steel (found in the same places) is probably also fine.Make sure the contacts are hidden away enough that something metal casually brushing by doesn't cause them to short out. The charger itself should be reasonably short-tolerant, but extra stress isn't nice on it.Could switch the supply by contact, so it only turns on once the dude is docked. Then it stays safe as long as nothing hits the switch.Tim