You sound a bit like my father, who was also an electrical engineer. Except his words of wisdom were often closer to, "... and when you get yourself in trouble, don't call me."
Originally Posted by polyglot
The good thing is that smart people can learn new skills. While your warnings are quite valid, perhaps a little faith that sufficient learning will be done prior to building the project. Electrical work does require knowledge, but its not something that requires advanced degrees to learn. Trust me... I'm not the most intelligent guy but I learned to do lots of electrical work. Electronic work is a different story.
I respect your conscience though.
The switch needs to be in series with the lights, which must be in parallel with each other. As for figuring out how much current is drawn, add the wattages of the bulbs together, then divide by the voltage and you'll get current (basic Ohm's Law: Power = Current * Voltage, or Current = Power/Voltage.)
I can draw up a schematic later tonight on how you'd wire this up in case a picture is needed. Tried doing an ASCII-art drawing and it just didn't work.
Absolutely smart people can learn and degrees are not required. I'm just asking that people do the learning first and don't go ahead and build things that they already know have a good chance of being quite unsafe. While I know from the OP's history here that he's a reasonably smart guy and could easily learn how to do this safely, the questions in this thread tell me in no uncertain terms that this lighting box has a good chance of ending up a deathtrap if built right now.
Originally Posted by BrianShaw
Simple electric circuits shouldn't be hard for those of average intelligence. Just remember two things: it can kill you if you touch a live wire, and to always unplug before you work on it.
The fan goes in parallel, just like all the lamp holders -- black to black, white to white.
The switch goes in the "hot" wire -- black (brown in EU) is hot, like burned stuff, white (blue in EU) is cold (neutral, return) like water, ice and snow and green like grass (with yellow stripe, like my lawn) is ground.
Now, with lamp cord, the one with the stripe should be hot, but only if you have a polarized plug on the end. That may be the only reason to use a 3-wire cord: so you always switch the hot. It's OK to leave the ground unconnected if you have no metal to connect to. Bring the cord in, connect the black wire from the cord to one side of the switch and the black wire from all your light fixtures and the fan to the other side of the switch. All the whites connect together and to the line cord.
You'll do fine.
polygot, I think your warning is a bit over the top.
True, I've never built anything electrical from scratch; just fixing broken things by soldering or reconnecting wires. But to abandon this project right here and now because I asked for advice is a totally ridiculous suggestion.
I'm not going to burn down my house, I'm not going to kill myself, and I guarantee I'll make a perfectly safe device. Maybe you should be warning about the dangers of potassium dichromate, since I've never had lab training either.
Sorry, don't mean to sound harsh, and I do appreciate your concern, but think back to earlier times when people cobbled together all kinds of apparatuses, and a darn good percentage of them lived to tell about it.
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Of course you can disregard any warnings and you'll probably survive. I don't have anything to say about dichromate because I'm not a chemist; as far as I'm concerned you're welcome to drink it
As to people hacking on stuff - I've seen so much horrifically dangerous DIY wiring that I stand by my warning whether you believe it or not. A good percentage might survive but there are a hell of a lot that didn't, including people who were not involved in the DIY efforts.
I say this as someone who reckons people should do more experimentation and DIY stuff, and especially they should hack on things they own. However, mains power is fickle stuff that can get to places that you really did not expect it to unless you know exactly what's going on. I'm not saying you should never ever work with the stuff, just that some electrical & electronic education is in order first, i.e. an understanding of basic circuits and exactly how grounding works as a safety feature, as a minimum. You also need to think of the mechanical failure modes (what happens when dropped, bumped, snagged on something; whether any parts like cords are subject to wear) of what you're building, how that might create electrical hazards and how to mitigate those in the construction. Please at least make sure you have proper strain-relief on the supply cord and that all internal cords are covered by a rigid case and therefore not subject to snagging.
I will do my best to make it safe polyglot.
I'm planning to use cord "brackets" or whatever you call the collars that go around cables and allow you to secure them to the base. Ultimately, this thing is only gonna be plugged in for exposures and only when I'm present of course.
Re: Dowel legs - holmburgers
It's likely you'll have to make those - really easy, though. Find appropriate sized dowels and get wood screw threaded studs and tee nut inserts like the attached. Wood screw threads go in the dowel, 1/4"/20 threads go in the insert that you put in the light base.
Edit: Also helps when I read the rest of the thread and see that the general idea has already been tossed around.....
Actually, I think I've found an even simpler solution. You can get these plates and screw in these legs (available in many different lengths).
I finished wiring this all up last night and well, I didn't burn the house down! I just need to get the legs, put some curtains around the sides and start exposing.
I'll post some pictures once it's all said and done.
Thanks for everyone's help; I needed it, and I'm pretty pleased with the result so far.