The FX Light Dimmer

Do you want to make some FX for something? Then make a light dimmer! It's simple, really ; all you need is some basic parts from your local hardware store. You can normally use a single switch for 2 lights, depending on the wattage rating of the switch. Please note: I am not responsible for any damages you do to your lights, your body, or the main power grid. We are dealing with 120 volts here, so take care. If anything does go wrong, you should only trip a breaker. Build this at your own risk!

Step 1 Materials

All of these materials I got from my local hardware store, Home Depot, in the electrical section. Total cost is about $18.

You need:
1 single-pole light dimmer switch - Find the cheapest one. Mine is a part number S-600-WH from Lutron.

1 two plug electrical outlet

2 old-work gang boxes

Faceplates - One for the dimmer, one for the outlet.

1 cheap extension cord - It doesn't matter if it has a ground wire, as we are only using it for lights.

Extra wire - Or you can use part of the extension cord.

3 Wire nuts

Tools:
Screwdrivers
Wire cutters/strippers

Comments

[jongscx]

On the surface, this works... but make sure that what you plug into it doesn't go over the rating on your components... otherwise, fire ensues...

[VadimS]

The week point is the scr in the dimmer. It's mounted to the aluminum (as a crude heat-sink) and it's not flammable. Worst case it overheats and smokes for a second.
Thay are designed that way so if someone replaces the 25w bulbs with a bunch of 200w or something it will fail non catastrophically.

On another note. It's against electrical code to have a 3-prong outlet attached to a 2 prong (non earthed) cord. I would strongly recommend a 3-prong cord, and metal boxes (metal boxes are cheaper anyway).

It's not like anyone checks but if your house burns down for any reason stuff like that can screw you (even if it had nothing to do with it).

This will fork on some motors without harm. Look for ones with brushes like drills etc.
But most larger motors have there speed determined by the ac frequency and all a dimmer will do is reduce there max power (but not normal power consumption) these motors either run at a specific rpm (1750 etc.) or just sit there and twitch if overloaded.

[csmail]

Is it okay to use steel electrical boxes instead of the plastic gang boxes that you've shown? (and by "okay", i mean "safe")

-charlotte

[carpespasm]

I'd only suggest it if you're using grounded power cables (three prong) and attached the ground wire to the metal cases. You usually do that by attaching the green screw on the outlet and green wire on the dimmer to the ground wire and screwing the dimmer and outlet into the box.

[qwertyboy]

probably, just as long as you make sure no wires are touching it

[drbill]

Well, being that this is not rocket science, to know the temp with this unit with any accuracy is not possible. However, if you take a bit of solder and touch it to the iron and it melts slow it's COOL. If it melts fast it's Hot. Try to think of it as a tiny foundry. I am a Ham Radio Operator. I build lots of cool stuff that works. Some of it has been "SMD". Very tiny heat sensitive parts that like to cook when heated too much. So, being that it is not possible to place heat sinks on these things, I do the next best thing. I lower the heat on the tip of the iron. Exact measurements? Not without buying a very expensive soldering station with a readout for temp. 73's KB1LZL

[qwertyboy]

oh, thanks. i might try it.

[drbill]

Oh. And your dimmer unit works with small motors too. Though I think it not a good idea to rely on this for long term use with motors. The dimmer will provide whatever your line voltage is down to about 95 volts. 73's KB1LZL

[drbill]

also good for solder iron temp control

[qwertyboy]

i've heard of doing that. how do you know the temp. though?

[strehlow]

I second what sdallesasse said. I'd add that providing strain-relief at the entry points to the boxes is very important. That will prevent tugging on the wires from pulling them off the terminals. For this it could be as simple as knotting the cord a couple times inside the box so it won't pull through. The best is using a commercial cord strain-relief grommet. They are very cheap.
I also typically use crimp-on spade connectors when putting stranded wire on screw terminals. If they are not used, pay close attention to make sure the strands are twisted tightly and none poke out after the screw is tightened.
An alternative (and simpler) design is to simply buy an extension cord and insert the switch box into the line, preserving the female end of the cord. Often pre-made extension cords are cheaper than buying the same length of wire and plugs separately.

I built a similar (though cruder looking) device many years ago to control a task lamp for my mixing console while doing live sound work. I've since used it often as a temperature control for my soldering iron.

[frollard]

Great project! I've built a few of these for lamps around the house... Worth noting is checking the packaging of your dimmer if it can be used for resistive loads (lights only, like yours) or inductive loads (motors, fluroescent lights etc). It will say on the packaging - keep this in mind when shopping for your application. General rule is that inductive dimmers will cost more. Also, this is just for ease of installation, when wrapping the wire around the screw terminal on the plug; (not sure if this is standard or just easier), to wrap the wire clockwise. That way, when tightening the screw (clockwise) it pulls the wire ONTO the screw, instead of pushing it OFF the screw.

[qwertyboy]

Thanks for your comment! That is a good fact to know, but i just grabbed the cheapest one i could find.

[jongscx]

So do inductive dimmers work via a PWM method like ESCs?

[frollard]

I believe they function on the same concept of pwm-ing the AC waveform once per cycle - but pwm on an inductive load doesn't like quickly changing currents (induced current = change in voltage vs time, when time is nearly zero (since the pwm is square wave), current goes exponentially up). It has some other protection built in for the huge back-reactance from the load.

specifically, I dont know exactly how they differ :D

[Derin]

and there is inductive kickback as well

[jongscx]

So they increase/decrease the wavelength while keeping the amplitude? or do they keep the wavelength the same but .... urg... I think my brain just deflated....

[frollard]

best description I've ever seen of how a dimmer work

http://home.howstuffworks.com/dimmer-switch.htm

[frollard]

basically, pwm based on the frequency of the AC waveform, only varying the duty cycle.

[sdallesasse]

You are switching the neutral! You need to correct this ASAP! Otherwise someone could get a nasty shock! Also you should have a cord with a grounding conductor (a green wire) in it. This is because you have a receptacle that is intended to accept a cord with a ground prong on the plug. That is for the safety of anyone who may be using a device that is plugged into the receptacle.

[qwertyboy]

ohh... i just noticed that. thank you. i just changed it.