Introduction: How to Make a Pull Switch.
A while ago I got a pool table in my shed, and I wanted to be able to see all the balls, so I put lights above it. I wanted a pull switch on the lights, but when I looked at buying one, they were worth about 50 AUD. More money than I wanted to pay for a switch really. So I built one. It worked well, but was a bit clunky and big. Recently, I put new lights over the table, and decided that it was a good time to improve on my switch. At the same time, I installed lights over my workbench, and I wanted a pull switch there too. So I'm going to show you all three switches.
Step 1: What You Will Need (general Parts)
Whatever you do, you will need a switch. I used Jaycar's bedlamp switch, this is just a push on push off SPST switch with a big white button on the front.
You will also need some kind of box, some cable, probably terminal blocks and some tools; lengths of aluminium perhaps, a sheet of perspex or some other rigid and preferably non-conductive material. You'll need some tools too, a saw, a box knife, some files, permanent markers, drills, screwdrivers etc. Just the usual basically.
Step 2: The First Switch
The first switch was very crude. It was a lever with a cord attached to one end, with a plate of perspex attached over two switches mounted in a box, one switched the each of the lights I had installed. The fulcrum of the lever was made out of a chunk of steel welded to a length of angle iron. I forgot to take a photo of it in place, but I have one of it after I took it off, the lever that is. You have to imagine a black box with two switches protruding from it. Basically, this switch worked, but it was noisy, clunky, and stuck up above the rafters, which I didn't like.
Hence switch 2.
Step 3: The Second Switch (read: First Switch MkII)
This is a vast improvement on the first switch. It's much quieter and smoother, and it doesn't go above the rafters, so I can stack stuff there again. On top of that, the lights are much better. All I really changed was the fulcrum, which is now a pair of aluminium brackets, one on either side of the aluminium channel stock. Also the switch position, It was an inch higher, meaning that the arm stuck up higher. It's much better with the switch mounted in the wood.
Step 4: The Third Switch (my Favourite) - the Plan
Instead of levers, the plan for this switch was to have a plate that was pulled down onto the switch by a cord, without any fulcrums or anything of that nature.
Basically, I wanted a plate with a switch mounted on it and to the enclosure, this will not move. Above this is another plate, with its centre aligned with the switch.
This plate is connected by four rods to a plate underneath the switch, which in turn is tied to a cord. The topmost and bottommost plates are attached so that they are completely rigid.
This means that you can pull on the bottom plate, and both plates will descend, the top plate pressing the switch.
Ideally, the plates won't tip sideways, but there's no guarantee. A spring at each corner will help minimise the likelihood of the plate tipping to one side.
Step 5: The Third Switch - Marking Out Etc.
The picture shows what I used for measurements, but you may need/want smaller or larger plates, or you might have two switches or whatever. The main point is that you want symmetry, and you want accuracy.
In case you don't know, to cut perspex, draw your line, then using a box knife or other sharp blade and a straight-edge, cut two or three times from end to end along this line. Then put the cut line over the edge of a table, or on a pencil or something, and snap the piece off.
Step 6: The Third Switch - Assembly
Put an M3 bolt through each hole in the top plate, and put a nut on the underside, as tight as you can. Now put a spring over each one. Put the switch into the middle hole of the middle plate and thread it over the bolts of the top plate, on top of the springs of course. Now screw threaded spacers on the underside of the middle plate; adjust the tightness of these so that the switch can be pressed properly, but only just, also make sure the plate is level. Now thread the cord through the bottom plate and screw the plate onto the spacers. Make sure there is a knot on the top side of the bottom plate.
The mechanism itself is now assembled. You now need to put it in a box. Mark out the holes on the box and drill them out. Using the outermost holes on the middle plate, and some spacers of an appropriate length, mount the mechanism to the box.
Now you need to wire it up. How you do this is up to you, as you may be wiring it for a specific purpose, voltage, etc. etc. etc.
However, I will say, if you are wiring it for mains, BE CAREFUL. Put the switch in the active line, and make sure there is no chance of anything on the outside of the box going live.
Step 7: The Third Switch - Installation
Pick a spot and put it there. That's about it for this step I'm afraid.