I’m making the Frequency central routemaster eurorack power strip. I’m all done with it except attaching the power cables from the 12VAC 1A wall wart to the strip. (this one for reference)
My plan was to get a DC barrel jack in the right size (this one perhaps) and then mounting it on my case to plug the cable from the wall into there and of course connect the jack to the board inside.
My question is, how can I tell which is power and which is ground? (Don’t do this at home kids, unless the comments say its safe) I plugged the wall wart into the outlet and got an LED and just tried seeing which way made it light (or blow) up. If I stuck the short lead in the middle and the long lead touched the outside it flashed and I assume burnt out. But the other way it did nothing so thats my scientific findings.
Any ideas? I know this is such a basic stupid question but I’m really at a loss here and have been trying to find the right way to google it for like a week now so nows the time to look a fool and learn instead of blowing up my power strip lmao.
Thanks everyone sorry if its incomprehensible jibberish.
I’m sure somebody else can put this more eloquently but,
AC doesn’t have polarity like dc. You could put the wires either way into the FC. But if you ever go back and add another FC unit to the same wall wart you can run into trouble if you hook them wrong
LEDs aren’t meant to be directly powered by AC. The frequency central separates the 12v ac signal into +/-12 DC
So from the jack I install, I don’t need to worry which goes to power and which goes to ground? Sorry this is my first non kit build so I’m still figuring this stuff out. Thanks for helping
It DOES matter — at least for some devices — on that side of the wall wart. One wire is hot, the other is neutral, and a polarized plug enforces which connects to what in the device.
But it’s a transformer, remember. No conductive connection between the input and the output of the wall wart. And on the output side, it doesn’t matter.
Is that wall wart actualy AC-AC or AC-DC , Sellers don’t know what they have half the time and the front of the device that would tell you is covered in the picture.
If it IS truly AC, then fine, connec either wire to GND on the route master and the other one to AC1.
The trick with the LED was a good approach to find out whether a power source is a DC or an AC source.
When connected to a DC source the LED will only light up if the polarity is correct and otherwise it won’t. So alternating the leads to the source will tell you whether the source is a DC source or not.
When connecting to an AC source the LED will light up irrespective of which lead of the LED you connect to which lead of the power source.
There are a few snags though. A LED can not survive if the voltage you apply to it is too high because then the current it draws makes it heat up too much and burn. Remember, a LED may almost never feel warm or hot (unless it is of a type used for lighting). Furthermore a LED does not like the reverse voltage (when the leads are connected ‘the wrong way around’) to be too high. That maximum reverse voltage often times is only a few volts!
To restrict the current you have to connect a resistor in series with the LED. To protect the LED from too high a reverse voltage you can connect a diode in opposite direction in parallel to the LED. For modern LEDs and low voltage power sources a 10k Ohm resistor should give a bright light at a small current. For older LEDS you will need a resistor of say 330 Ohm.
The anti parellell diode restricts the voltage across the LED to 0.6 V so the ‘reverse’ voltage on the LED will not exceed the limits of the LED (which might be only a few volts).
If in stead of an anti parallell diode you use another LED, you can see in one glance whether you have an AC or DC voltage source. An AC source will light up both LEDS, a DC source will light up only one. If you use a GREEN LED in forward direction and a RED LED in reverse light, you can immediately see which lead is positive and which is negative.
Many years ago I bought a set of test leads which are based on these ideas. The resistor used in the device is a varistor (a resistor whose value increases when you apply a higher voltage to it) which makes it possible to use the test leads across a large range of voltages (3 - 400 V).
This is what I did for my power supply panel. I did notice the jack getting loose after awhile planning on replacing it with another connector. Notice how I heat shrunk the AC section and Switch to a make sure nothing can short out in the 12v AC section. Since it is a transformer It is not electrically connected mains precautions are always good to take. Power Supply Panel Hack a day
So… I don’t really want to buy heatshrink if I don’t have to. I will if I have to. But could I just hot glue the connector after I soldered the wires? Or electrical tape? I have both of those but not heatshrink somehow haha
sorry if its incomprehensible jibberish.
