Gooseneck Light and Magnifier
Gooseneck Light and Magnifier
In this Comment/How-to I describe making a light and magnifier mounted at the end of a flexible metal pipe, commonly called a "Gooseneck".
I had always wanted one of those "helping hands" which incorporated a light, magnifier, pcb holder and crocodile clips into one many-armed unit. So I searched for the net for one. The commercial offerings did not quite meet my needs so I built my own.
I already had a small vise, which I fastened to one side of a piece of plywood. This would serve to hold PCBs while soldering. Later, when I purchased a drill stand for my 12 Volt motor tool I mounted that, too, to the same board.
It was hard to see the drill bit while trying to align it with the mark on the board being drilled. I needed light. Some magnification would come in handy, too. An added bonus would be protection, should the drill bit break and pieces fly around at high speed.
This is a unit which provides light, a lens, and protection from flying bits of metal. It also serves as a "power hub".
Catch a goose, and cut off its head and body. WAIT! There has to be an easier way.
One source for this component is the USB flexible lamps intended to be plugged into your laptop to light up its keyboard, and help you "look and peck" in the dark. EBay usually has a good selection at competitive prices.
The local computer shop had presented me with this usb powered light, I guess, in order to bribe me to keep patronising them. I wasn't entirely happy with it, since a hard knock on it while plugged in could potentially break the usb socket off my laptop main board. The usb plug was flimsy and making intermittent contact, so when it finally stopped working I scrapped it without trying to repair it.
The one useful piece from it was the gooseneck. Bright, plated steel, around 300mm (One foot) long, 5mm dia, it was gracefully supple. But how heavy a load will it support? A quick measurement using a digital scale told me that it took around 50g of force before it started bending. Anything supported by it will have to be kept well below this weight in order to prevent the gooseneck from drooping from the strain.
I found a thick piece of plywood in the trash about 170x110 mm (roughly 7"x4") and decided to build my gadget on it. The simplest method would be to drill a 5mm hole and glue the gooseneck in with epoxy, but I wanted to be able to take it apart for modifications. I decided on a screwed connection: glue a nut into the plywood and a threaded sleeve onto the end of the gooseneck, and they may be taken apart and fastened securely at will.
The parts are from an F connector. I took these off a cable tv rf splitter. The end of the connector was filed off and the innards removed, and the gooseneck fastened with two component epoxy putty. I'm a great fan of this stuff, and I use it for almost everything - especially on wood.
The first picture shows the connector, the second is it broken apart and the third is an arrangement on a corner of the plywood base. It is a sort of dry run, moving it about for the most pleasant visual effect before drilling into the wood and making it permanent.
The Gooseneck Tip
- RCA plug: This is part of the interchangeable head
- Soldered together
- Glued together
- RCA Socket
Since the end of the gooseneck is to carry a light, or a magnifier, or both, or something else that i haven't thought of yet (but sure will) I decided to make the tips interchangeable. The juice to make the light shine is carried to it via wires running up the inside of the gooseneck. If it terminates in a socket, different heads could be plugged in. I decided on a RCA connector because I had a bunch of them from damaged cables.
It is difficult to make a soldered connection to steel, so I decided to solder a brass tube to the connector, and epoxy that tube to the end of the gooseneck. So first I soldered a brass tube to an RCA socket, along with the wires, holding it in my small vise to avoid burning my fingers. I used a piece of wood to insulate the socket from the iron jaw of the vise, or otherwise my soldering iron wouldn't be able to heat it up sufficiently to melt solder. This assembly could then be fastened securely to the end of the gooseneck with two component epoxy putty.
Drilling the Base
The edges of the plywood were prone to flaking off, so I sealed them with a liberal application of epoxy putty. I filled in scratches in the top, too, because there was some left over which would otherwise have gone to waste. It makes for an interesting pattern as it highlights the grain of that top layer of plywood.
The hole for mounting the gooseneck was bored with a wood chisel bit, half way through the top and then again from the side, to meet in a sort of L shaped hole. I excavated a rectangular cavity to fit a slide switch in - it might come in useful.
Other holes were bored using a piece of coat hanger wire, linking the corners, so that I could have plugs or sockets there - to feed another lamp, perhaps. Or a low voltage soldering iron. Or a fan to blow the smoke away from my face. This makes the unit a "power hub".
I enlarged the hole for the gooseneck sufficiently to hold the nut, then coated the inside of the hole with epoxy putty and forced it in, being careful to keep it level with the top. Extra stuff was carefully cleaned away. It is easier to shape it while it is uncured, and soft. Then it was left to set for a few hours. I did this on an evening, then put it away until the next morning.
The Gooseneck Assembled
The picture shows the various bits described so far, laid up prior to gluing in place. Once the head of the gooseneck is epoxied in place, it is going to be very difficult to make any changes to it.
One change I would like to make at this point would be to make the base, too, a connector so that screwing it into the base would simultaneously make the electrical connection. I think it can be added afterwards without dismantling anything, since the base of the gooseneck is a threaded part. The connector could be screwed to it, and will not materially affect anything else.
All Wired Up
I've wired up the switch and a few connectors in this photo. The wires are in place. The extra length has to be trimmed, ends joined, and made pretty. The switch is center off. One side connects the supply directly to the gooseneck, for full brightness, and the other position through a resistor, for reduced brightness.
I have also included a couple of the "interchangeable heads" in the photo. So I shall start to describe them next.
Weighing My Lenses
The gooseneck can support a maximum of about 50 grams without bending under the strain. I started weighing (!) my options for the magnifier part of the head.
My largest glass lens was over a hundred grams. Definitely can't be used. A smaller one was around fifty grams. Again, this is too heavy.
But there is hope: There was a pack of credit card sized plastic fresnel magnifiers I had purchased on a whim. I usually carry one around in my pocket. Six of them weighed about eighteen grams, one being just three grams. So these were selected.
Selecting the Lights
There were a few options for the lights. LEDs were definitely to be used, and filament lamps or fluorescent lights weren't even considered.
So, what number and type?
I had a soldering iron and a motor tool, both working at twelve volts. I fitted a motor to the drill stand and it, too, would operate at 12V. So it made sense to operate the lights, too, at twelve volts. I could just connect one 12V power supply and use it to power everything.
In the picture, the larger LEDs are actually multi chip modules with integrated resistors, rated for 10W, 12V. Using them is easy. Just connect to 12 volts, and they give out light, absorbing about ten watts.
But here is the not-so-easy part: they get HOT! And need a properly sized heat sink. They were too bright to be used so close to the work anyway. The heat sink would take up the weight to well above fifty grams.
So to discretes: the small LEDs in the picture are rated for one watt each, and may conveniently be soldered to the heatsinks, which may be mounted on the head. They need current limiting.
LED and Resistor Calculations
The supply voltage was already fixed at 12V because I had other things running at that voltage. Discrete 1W white LEDs were selected, mainly because I had a bunch of them I bought on "sale".
It is disconcerting to find your bargain pack of LEDs being advertised at half the price a few months later.
So, use them up as fast as possible, before they become worthless :-).
One white LED (which is actually a blue LED with a phosphor filter over it) drops about three and a half volts. A one watt LED can therefore handle about 1W / 3.5V amps or roughly about three hundred mA (286 mA, to be exact).
Actually, this is the current level above which the manufacturer guarantees his device will blow up. To be safe, it would be wise to run the device below about 250 mA.
It has to be kept cool, or otherwise it would stop working. This requires that they be mounted to a piece of metal large enough to dissipate the heat by convection to the surrounding air.
Three LEDs in series would drop about 10.5 volts. 12 - 10.5 = 1.5 . I need a resistor which would pass 250 mA when it has 1.5 volts across it. 1.5 / .25 = 6 ohms. That resistor would be dissipating 1.5 x .25 = .375 W. A half watt resistor would be suitable. This is an approximate calculation, and should be verified by actual measurement before committing to the circuit. I suggest starting with a resistor much larger than calculated, measuring the voltages, and revising your calculations based on the measured value.
In my case, measuring the voltage drop of the three LEDs with a 100 ohm resistor in series, gave me a value just above nine volts. Trying various resistors, I determined that a ten ohm resistor will result in a current of about 230 mA, and that at that current, the three LEDs dropped about 9.5 V. The three LED voltages were all slightly different, between 3V and 3.3V.
A quick lash up and test confirmed that this would give out sufficient light for my purpose, without being dazzling bright. So a ten ohm resistor was selected, and soldered in.
Constructing the Head
- 1W LED
- 10 ohm 1/4W resistor
- Aluminum heatsink / reflector
- A close up view of the fresnel lens
I selected a piece of aluminium plate, cut off a length about as long as a credit card and bent it to an L shape. Together with three LEDs, it weighed less than nine grams. The three LEDs were then glued to the plate with epoxy (Araldite) to dissipate the heat. The 10 ohm resistor was wired in.
A spring holds the credit card sized fresnel magnifier in place. This is made of soft plastic, and scratches easily. So it makes sense to leave it off the head for the more dusty operations. The lens is formed by circular shaped grooves and if any dirt settles in there it is very difficult to clean it without damaging it in the process.
The RCA plug was glued to a piece of tube from a ball point pen body, and this tube was in turn glued to the heatsink. I used two component epoxy. Connections were made to the ends of the LEDs and the resistor.
These pictures show my "failed attempts". I'm sharing my mistakes so that you don't have to make them.
The first is a head I made by soldering together the LEDs from a 12V LED strip. This was dismantled from a shelf, and some of the lamps were unlit so I had the bright idea of desoldering them, and fitting them all close together to make a high powered lamp.
It worked, but it was too much work. There is no way to replace one if it goes faulty. High power LEDs are available and are more economical when used for the same amount of light. This assembly has sixteen strings of three series connected LEDs and resistor - a total of 48 LEDs and 16 resistors. Definitely a labour of love.
Considering that three LEDs with one resistor can be wired up to give about the same amount of light, I would not recommend that you attempt to duplicate this one.
Smaller LEDs are useful for distributed lighting, and that is the way they should be used.
The second was my bright idea to have just one 1W LED with an aluminum reflector. I wired in a series resistor to make it work at 12V, but neglected to calculate the power rating. It worked, but the resistor failed in a cloud of black smoke.
Let's see: One LED drops 3.5V, so the resistor has to drop 12 - 3.5 = 8.5V. For a current of 250 mA, it has to be 8.5 / .25 = 34 ohms - I used the nearest preferred value of 33 ohms.
It dissipates a power of 8.5V x 0.25A =2.125W - ie, more than two watts. i was overloading that little resistor!
So the lesson is, ALWAYS calculate power rating of components when wiring up circuits handling appreciable amounts of power. Like LED lighting circuits. Otherwise, the surprises you get might be unpleasant.
Tools and Materials
- 180 - 400 - 800 - 1500 grit sharpening stones
If you have scrolled through to this part of the Comment/How-to, you are probably interested and thinking of building one for yourself. What do you need?
Junk. Lots of Junk. Lots and lots of it. Broken things that sane people throw away ;-). Look through your collection once in a while, trying to arrange it and make some sense and order out of the chaos and maybe inspiration would strike you in a blinding flash. (In my case, however, the collection gets even more jumbled after an effort at "cleaning up".)
In general, electronic components from junked electronics aren't very useful. Except for resistors, connectors and hardware.
Ebay is good for things that AREN'T broken. I've seen broken things advertised too, and returned a few that were advertised as good but turned out to be broken on arrival.
I used a portable drill and a set of drill bits. It is reversible, has variable speed and a keyless chuck. A useful accessory was a spindle that takes disks and pads intended to be used with angle grinders. I store my drill bits in holes drilled part way through pieces of wood. When it is time to put them away, I can see at a glance whether any have gotten misplaced or lost.
I bought a set of carving chisels and a set of grinding stones to sharpen them. I used them to carve out the slot for the switch, and to enlarge holes made by drilling. Keep them sharp, always, or your cuts will look as if a dog chewed on them. A dog in a particularly nasty temper.
Long holes through the plywood were made by drill bits made by flattening and sharpening a length of coat hanger wire. This sort of thing is highly dangerous, so I shall not go into detail.
A stainless steel scraper was useful for spreading glue, wood filler, epoxy etc to get a smooth finish. I keep its edge square and smooth and honed to a mirror finish. The plastic handle makes it comfortable to hold and use.
Here is a list of materials that I used:
1. Piece of plywood, from the trash
2. Gooseneck, from a defunct USB lamp
3. F connectors, from my stash of junk
4. RCA connectors, from my stash of junk
5. Wire in two colours, from my stash of junk
6. Two component epoxy putty, white, from the local hardware store
7. 60/40 rosin cored solder, from the local electronics shop
8. LEDs from ebay
9. Resistors from my stash of junk
10. Credit card magnifier, from ebay
12. Assorted bits of metal and plastic, from my stash of junk
13. Three position slide switch, from my pile of junk - pulled off a chinese lamp.
14. 12V 1.5A power supply - originally belonged to a scanner
Here is a list of Tools:
1. Electric drill and drill bits
2. Carving chisels
3. Putty knife
4. Soldering iron
5. Wire cutter and stripper
6. Combination pliers
7. Motor tool, with grinding wheel
9. Digital scale (weighing machine)
10. Junior saw and hacksaw
I used my mobile phone to take all the pictures for this Comment/How-to. But I used it in the way I would use a proper camera - for most of the shots, it was on a tripod.
Having the camera - I mean, my phone - securely supported allows me to arrange the scene leisurely, to put across the idea I am trying to convey, and ensure that slight movement of my hands haven't thrown my picture out of alignment. I have set it up to take the picture a few seconds after I hit the button, so that vibrations can die away.
I try to have the light diffused, but directional. The idea is to have well defined shadows, but enough light to be able to see the detail in the shadows. Sometimes i will put a white plastic cover over the scene to hide the clutter just out of view. This also has the bonus of diffusing the light.
As in the picture above, there is a lot going on just outside the area the camera is aimed at. But I try to ensure none of that gets in the picture to confuse the viewer.
Like all good things, this Comment/How-to, too, has come to an end. Thanks for reading through to the end.
I started on this project after looking for "helping hands" on the net. They all come with bases. Bases take up too much space on my workspace. I don't have a dedicated workspace, and have to put my things away and clean up the mess I inevitably make.
With this one, the base is the workspace. I usually work with very small circuit boards, around a few inches at most, Things I use have to fit into the smallest space for storage. This paucity of space is reflected in the design.
Since it was for the Comment/How-to, I took special care to make this tool look pretty. Usually most of my contraptions I make for my own use are ugly and functional, and they get dismantled or gutted for parts soon after.
Putting some effort into making it look pretty has made it more pleasant to use, and this one might stick around for a little longer.
I hope to share more things I make, and soon.
Acknowledgments, Credits, and Bibliography