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Quick question for EE guy, 5volt, USB, soldering, etc (solved)

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spystyle:

--- Quote from: Mysterioii on July 23, 2012, 02:45:24 pm ---It says it's rated for 10A at 120VAC so if you need less than that, yes.  Assuming you actually get what it's rated at and not random Chinese knockoff junk.
--- End quote ---

Hey thanks for chiming in :)

Can you tell me how I'd wire it ?







I'd guess like so :

4-1 = black
2-5 = PC (12v)
3 = N/A ?

And therefore only 1 wire from the power strip needs to be interrupted ?

I need to go to EE skool :)

Thanks,
Craig

P.S. Also your correction was very interesting

EDIT :

Pins 1 to 4 are "normally closed", and pins 1 to 3 are "normally open"

So for a power strip hack =

1-3 = black
2-5 = PC (12v)
4 = N/A

... and try to keep it under 5 amps :) Or buy a better relay.

MonMotha:

--- Quote from: Mysterioii on July 23, 2012, 02:45:24 pm ---You should be able to stick a bare wire in the neutral terminal and hold it in your mouth then stick another wire in the ground terminal and hold it in your hand and be just fine.

--- End quote ---

For the record, don't do this.  It's common even in residential environments to get several volts between neutral and ground due to voltage "drop" across the neutral from the current flowing on it.  The ground (ideally) has no current flowing on it, so it doesn't see the same drop.  In industrial and commercial buildings, the situation is even nastier.  There's only one bond point between neutral and ground (where the power enters the facility).  The neutral and ground are then bussed to each sub-panel separately.  You can easily end up with 20-40V difference between neutral and ground in these environments.  It'll certainly give you quite a wake up if you touch both of them, especially on your tongue :)

"Ground" should always be touch-safe.  That's the whole point of it.  It's the current sink of last resort and should always be at local earth potential.  Neutral is bonded to earth ground at your main panel, but things can start to diverge from there.  Hot of course is 120Vrms relative to neutral (and hence approximately 120Vrms to ground, since neutral and ground are "about the same").  The only real difference between hot and neutral is that one of them is hooked up to a big metal spike driven into the ground, but the implications of that difference are pretty far reaching, and the entire electrical safety code is designed around this.

As for the relay in question, there's no way I'd use that tiny little relay for this purpose.  One, I don't like the pinout structure - it requires having 120V too close to the isolated 5V for my comfort.  I also don't really trust that tiny thing with 10A.  Heck, I'm not sure I'd trust it with 5A.  Your wiring description is correct, though.  If you want some cheaper relays, check out places like Jameco.  They've got some surplus stuff that can be way cheaper than Rat Shack.

Mysterioii:
Haha yeah I admit I was being melodramatic...  my main point was that hot and neutral are not interchangeable even though I have come across several conversations over the years where people seem to believe that they are.  Making contact with the neutral conductor should be much safer than touching hot on a properly wired outlet but hopefully nobody would lick one based on my rant.

Re: the relay....  Yes sorry, I'm skeptical too, hence my "Assuming you actually get what it's rated at and not random Chinese knockoff junk" comment.  I should have been more clear with my skepticism.  I'll buy LEDs and stuff like that off of ebay but for something like a relay that's going to be carrying mains power I'd be more careful.  If you can find it at a digikey, mouser, newark etc. then I would trust it for sure.  However MonMotha you said:


--- Quote ---there's no way I'd use that tiny little relay for this purpose
--- End quote ---

If you look at the spec sheet, this relay is 2cm x 1.5cm x 1.5cm, that's pretty small but not exactly tiny.  The spec sheet makes a point that one of it's selling points is a small footprint.  Yes, it's meant to be through-hole soldered on a board and I prefer the socketed relays like the first ones he was using, it's much easier to swap one out if it goes bad.  I did a search on mouser.com for industrial relays with a 12Vdc coil voltage capable of handling 120 VAC at 10 amps or more and found several, both socketed and through-hole.  Here's a panasonic one that's almost the same form factor as the one he's looking at:

http://pewa.panasonic.com/assets/pcsd/catalog/js-catalog.pdf 

Again, would I be skeptical?  Maybe.  With mains voltage I'd probably pay a little extra and get them from a big distributor and not off of ebay.  But if I did get them from a known-reliable source then yes I'd have faith in the specs.

DaOld Man:

--- Quote from: spystyle on July 23, 2012, 04:43:15 pm ---
--- Quote from: Mysterioii on July 23, 2012, 02:45:24 pm ---It says it's rated for 10A at 120VAC so if you need less than that, yes.  Assuming you actually get what it's rated at and not random Chinese knockoff junk.
--- End quote ---

Hey thanks for chiming in :)

Can you tell me how I'd wire it ?







I'd guess like so :

4-1 = black
2-5 = PC (12v)
3 = N/A ?

And therefore only 1 wire from the power strip needs to be interrupted ?

I need to go to EE skool :)

Thanks,
Craig

P.S. Also your correction was very interesting

--- End quote ---

For your case, you want to connect the black wire from the 120 vac plug to the pin #1 and the black wire from the power strip to pin #3. White from plug and white from power strip connect together.
Pins 1 to 4 are normally closed, and pins 1 to 3 are normally open. The power strip will turn off when the relay is turned on if you use pins 1 to 4.
Also, in US anyway, breaking the neutral wire (usually white) on the power strip is not necessary. Just control (or break) the black wire with the relay, no need in doing more work than you really need to.

Edit: I would not use the small relays with the pins, simply because it is going to be tough soldering a #16 or #14 AWG stranded wire that is on the power strip to those small pins. That relay is designed to be mounted on a PC board, where the pins on the relay go through solder pad holes on the PC board.
It can be done but it is not desirable. Plus (due to heavy gauge wire sucking up the heat), you will have to use a hot soldering iron to get a good joint, and that relay may not like the high heat.
I would go with the "cube" relay from radio shack, it has terminals that you can solder a bigger wire to fairly easy, although you may have to drill out the holes in the contacts for the bigger wires of the power strip to fit.

spystyle:
Thank you all for chiming in :)

I appreciate it :)

Craig from Maine

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