Wiring Pen




Introduction: Wiring Pen

About: I'm Chandra Sekhar, and I live in India. I am interested in electronics, and building small one-off circuits around tiny chips (the electronic kind).

Attach a spool of wire and a hypodermic needle to a ball point pen barrel to make an aid to make point-to-point wiring easier to do. The board shown is a microprocessor system board with a 8085, 2764 and 6464 - that is, the CPU, EPROM and RAM - and some additional glue circuitry.

Step 1: The Parts

A hypodermic needle. Get the disposable type with a plastic collar, as this will need to be cut down to make it fit in the nozzle of the ball point pen.

A (used) ball point pen. I acquired one with a metal nozzle as it would probably last longer.

The spool of enamelled wire was from a relay, 12 V changeover contacts - the rest of the relay was dismantled with care not to damage the spool of wire. Other sources are transformers and rf chokes.

Some two component epoxy to cement the needle to the nozzle.

A screw long enough to hold the spool of wire (not shown)

Step 2: Putting It All Together

First, some copper wire was placed inside the needle to prevent its bore from closing up, and its sharp point was ground square on some fine emery paper.

Its plastic collar was cut to make it fit inside the nozzle of the ball pen, and it was fixed in position using some two component epoxy glue.

The screw was heated and poked into the side of the pen, and on cooling it was unscrewed. The spool of wire was placed on to it, and it screwed back on. The wire was led through the body of the pen and out through the needle tip.

The thin tip of the wiring pen enables it to be used to snake the wire through tight spots, and to make connections to tightly packed integrated circuit socket pins.

To make a connection, the (enamelled) wire is wrapped once or twice round the ic or socket or component pin. Heating the joint, and applying some solder will complete the joint - if you are lucky enough to find some 'self fluxing' enamelled wire. This sort of wire is coated with the sort of enamel that changes to flux when heated to soldering temperature.

I prefer to use normal, tough enamelled wire, as the chances for accidental short circuits is reduced while using this type of wire. The joint has to be heated and then the enamel can easily be scraped off using a sharp edge of a small jewelers screwdriver. Then solder is applied and the solder will attach to the freshly exposed copper.

I used to make all my prototypes this way, until the coming of the flash microcontrollers with on chip program and data memory, which does not need this scale of wiring in order to work.



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51 Discussions

That's ridiculous. What do you do if you're diabetic?

If they are illegal where you live, you could probably get away with using an inflation needle, like you would use to pump up a soccer/volleyball/basketball with.

Not in Canada at least. We can go to any hardware, drugstore, or even the dentist for just one or two. I can also find them at pet stores sometimes, and the flooring department at most warehouse stores. You use the large 50CC ones for flooring, to apply glue to area's that are bubbled. Either way, they will have those metal tips you're looking for.

That depends where (and who) you are. some places put legal controls on the possession and transfer of hypodermic needles. this has changed with the spread of HIV Blunt hollow needles are legal most places, they are used in things like inkjet refill kits. It may be possible to roll a needle for this instructible from stainless steel shim (eg the sliding cover of a 1.44MB diskette) as the needle is just used as a guide for the wire.

the last time i checked you can't buy hypodermic needles off the shelf anywhere legal. and besides how would you get a hold on one legally

I got a free one from a pharmacy to apply acetone to an acrylic box joint, and I think the pharmacist actually believed me when I said it was for a science project. Beforehand I got turned down by a walk-in care place--they did not believe me.

You can also buy non-super-sharp ones in bulk from mcmaster or places that sell solder-paste dispensing syringes.

I'm sure all the Type I Diabetics are plenty of proof that they're NOT illegal. Just because something is not convenient or easy to find doesn't mean it's illegal.

you can find needles at farming supply stores, pet supply stores, pharmacies, vets, etc. They are not illegal in most places in the U.S., though if you are caught with some drugs and a needle it will probably be called paraphernalia

I would guess that any reasonably-stocked pharmacy should have these (behind the counter), not every diabetic has an insulin-pump, so manual injection is vitally important. Professional piercers also use a variety of sizes of hypodermic needle, anywhere from 20ga all the way up to 2ga (or at least I've never seen anything larger than a 2)

that's because there isn't exactly an enourmous market for over-the-shelf hypodermics, but i haven't been to a pharmacy - i am sure if you looked around you could find somewhere to buy them in person. just do a little bit of google searching, you can easily find perfectly legal medical supplies without any need for you to fax them your phd or something stupid.

If you can't get a hollow needle, try it with a propelling pencil with a metal tip. Or you might try using the tip of a ball point pen after emptying the ink out, and use a needle to pop the ball.

This stuff is pretty amazing and reasonably priced. They have it in basically all sizes.


Point-to-point wiring at the prototype stage or one-off project is far easier than techniques like stripboard. I have been doing an 8-digit 7-segment LED counter with a 24 pin Maxim driver and 28 pin Atmel (Arduino) chips. I soon gave up stripboard (too much scope for errors) and dug out my old wire-wrapping gear.

I'm glad I kept it as the component parts are available now, but inflation has taken it's toll - original wrapping/unwrapping tool £80 for example. The wire is also available as Kynar covered 0.5-mm diameter. It's biggest advantage over enamelled wire is its clean stripping and silver-plated copper core. It's much finer than stuff like CAT5e and the Kynar sheath is very tough. The stripping tool is simply a piece of thin steel with a "V" notch.

I also stocked up years ago with needles and syringes. Like many other things that used to be easily available, including most chemicals, the bad boys have queered the pitch for legitimate users - nitrous oxide will be next. ID to buy contact adhesive?? Loctite used to do blunt needles for some of their superglues and you can get stainless steel tube right down to 1/16 inch OD.

if anyone could come up with a way to combine this ible with
i would be very grateful...