Main > Everything Else
Quick question for EE guy, 5volt, USB, soldering, etc (solved)
spystyle:
Hey Monmothma,
Care to identify the polarity of this one ? It's a 12v IDE to USB adapter, I want to solder a molex to it :)
Thanks!
Craig
crashwg:
The one closest to the jack (and the one on the same pad) are ground, the one below is +.
spystyle:
Thanks :)
I would have deduced that from looking at the other one, but I thought maybe this plug was different so it would be reversed polarity - I guess not.
I need to go to EE skooL :)
Have fun!
Craig
spystyle:
Dear EE guys, I need your brain power again :)
Can "HJR-3FF-S-Z" (HJR-3FF) relay be used to make hacked power strips ?
Here is the datasheet :
http://www.datasheet.co.kr/datasheet-html/H/J/R/HJR-3FF_TIANBOGANGLIANELECTRONICS.pdf.html
They are really affordable, like $1.10 each :
http://www.ebay.com/itm/3-x-Mini-Relay-SPDT-5-Pins-12VDC-10A-120V-Contact-USA-Seller-Free-Shipping-/221040166504?pt=LH_DefaultDomain_0&hash=item3377054668
I currently use "275-218"
http://www.radioshack.com/product/index.jsp?productId=2049722
And that's nearly 10 bucks each.
Here is how I solder the pins :
"White" is AC white wire
"Black" is AC black wire
and "PC" is 12 volts from a computer
When the computer is turned on, the 12 volts activate the relay, and white is connected to white, and black is connected to black.
Can I get a clue from an EE ?
Thanks :)
Craig
Mysterioii:
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.
BTW reading back through this thread I saw what I believe is some well-meaning misinformation from 2 years ago... When talking about why coaxial power plugs generally have the power contact on the inside...
--- Quote ---On it's own it's no safer than the reverse, but since the negative is usually "common", protecting the positive side in all equipment prevents shorts when two different units touch. Just like AC wiring in your home, you designate one wire as hot and the other "ground" even though they're both 120v potential.
--- End quote ---
Hot and ground/neutral/return are not equivalent and are not at the same potential. You protect the hot pin in case for example you're making another path to ground like say you're plugging the thing in while standing barefoot in a puddle. If you're like a little kid and you're holding the plug wrong, you'll just touch ground and everything's fine. Same reason appliances have chassis ground. You ever encounter a stove, oven or microwave with the chassis ground hooked up backwards? Touch it while you touch the kitchen sink and you'll know it. When properly grounded that won't happen.
In your house wiring hot and neutral are NOT both at 120v potential. Apparently this is a common misconception? Get a multimeter, stick one probe in the center ground terminal, then probe the hot and neutral ones. The hot one will read about 120VAC and neutral will (quite sensibly) read zero. Unless someone wired the outlet backwards. I really hope people aren't wiring up there plugs backwards thinking they're interchangeable. For driving an old appliance with a simple AC motor yeah it might seem like they're functionally interchangeable but there's a big difference.
You will hear the argument that "current flows both ways in an AC circuit", and that's true, but only one side (the hot side) is driving the current. Imagine a garden hose with a pump on one end and the other end just dangling off into the grand canyon, just big reservoir for air just like earth ground is a huge reservoir for electrons. Air can be flowing back and forth in the hose at any point in time... the current is going both ways. Now cut the hose... The sucking and blowing (huh huh) is only taking place on one side, the pump side. That's hot. The other side of the hose... nothin'. That's neutral. One of them is safe to hold up to your eye socket, the other one wouldn't be a good idea. 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.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version