simple electronics question (to some, i hope)

[robbudo]

I am in the process of preparing for halloween and bought a 120VAC sound activated 3 channel color organ kit. I put 99% of it together just fine but I have 2 questions before plugging it in.

First, I am not sure which way to orient the plug that goes to the wall (to 120VAC). One lead goes directly to a fuse, and the other essentially goes to the rest of the board (transformer, capacitor, etc). I don't know if it matters if i connect the ground prong from the plug to one connection and the hot prong to the other. I figured i would double check before i decided it didn't matter.

Second, there are 3 AC outlets on the board (to which i will connect 3 strands of red LED christmas lights), and i DO know this is important because the directions say it is, although I can't make out the picture that tells me how to orient the plugs. Again, there are two choices, the positive terminal (from the short/narrow prong on the AC outlet) goes either directly to the SCRs (silicon controlled rectifier) OR coupled with the leads from the other plugs and then going to a neon lamp, a couple of resistors, and then the fuse mentioned in my first question.

I hope my explanation was sufficient and that one of you has a few minutes to help out a newbie.

rob

 

[flatulent]

For the mains connection, the fused wire should go to the "hot" socket pin and not the "neutral" pin. For the LEDs if you put them in the wrong way they will not emit light, so just reverse the connection. If you have a voltmeter and a power supply, determine which pin is the positive and then with the supply which wire from the LEDs needs the positive.

 

[robbudo]

Thanks flatulent. The first answer is straightforward and what i thought, thanks for confirming it.

I'm still a little fuzzy on the answer to the second question. As for the Three AC sockets that get plugged into the board, you're saying that plugging them in the wrong way (and powering up the board) won't damage anything, so i can just go by trial and error.
However, I do have a voltmeter. So, i could plug in the circuit board to 120VAC, and then i'm not sure what to do to check to see which pin is positive.

thanks, rob

 

[tigrek]

LEDs
the short leg should be negative. Looking from the top flat side is also negative
or
h**p://acept.la.asu.edu/courses/phs110/expmts/exp13a.html will show it

 

[robbudo]

sorry for being unclear;
they arn't 3 little LED lights, i will be plugging in 3 strands of christmas lights.

 

[flatulent]

It looks like your tree lights are designed to run on AC and therefore have built in rectifiers. These therefore probably are not polarity sensitive and will work with either plug rotation.

 

[robbudo]

I'm worried because the instructions say "2. install AC outlets as shown in the included illustration", but the illustration is as clear as fog at midnight.

 

[johnyaya]

Lets see if this will help:
There are 3 wires used for 120Vac power; hot (black or brown), neutral (white or blue), and ground (green or green with a yellow stripe). If you are using the non-grounded plug (one spade is larger than the other) then the small spade is hot and the large spade is neutral. You should usually fuse and control (your SCRs) the hot side. Neutral is very similar to ground and in most cases are connected together in the breaker panel. Almost all circuits designed for AC power will funtion regardless of polarity. Many do-it-yourselfers (and some electricians too) mis-wire AC outlets, swapping the hot and neutral leads. Your LED Christmas lights wont care which side is hot, but one should always wire the outlets according to the standard.

 

[robbudo]

Hi folks, thanks for the help and all is working well.