Forget Treating Your Diabetes – Use Your Insulin Syringe As A Logic Probe


Hackaday reader [JumperOne] was in need of a logic probe that he could use to reliably test some tiny .5mm pitch IC pins. The probe that came with his oscilloscope was a bit too big and not near sharp enough to do the job, but he figured that a syringe might do the trick nicely.

He drilled a small hole near the business end of the syringe, through which he fed a piece of stripped twisted pair cabling. [JumperOne] then soldered a pair of pins to a small piece of coaxial cable, attaching the opposite end to the twisted pair already in the syringe. After carefully coiling the thin cable around the needle, he secured the coaxial cable and its pins in place with a bit of hot glue.

[JumperOne] says that his makeshift logic probe works very well and the sharp needle would easily pierce through any oxidation or solder mask that stands in its way. One extra benefit of using a syringe as a probe is that they come complete with caps which help protect both ends of the delicate tool.

35 thoughts on “Forget Treating Your Diabetes – Use Your Insulin Syringe As A Logic Probe

  1. i am surprised that medical devices like that are not controlled hardware requiring an id or prescription to get.

    it may be easier to use a sewing needle or pin (same one used to remove slivers from your hand) and an inkjet filler syringe.

    1. Why would they? The synringe itself has no medical properties. It’s no more dangerous than a sewing pin. Heck, you can buy a beer keg and tap without ID, it’s only the beer itself that gets you carded.

      1. Not to mention that making needles harder to get just causes addicts to use reuse dirty ones. If they already have drug to inject, trying to prevent access to needles does no one any good.

    2. While attending medical checkups over the years, I often asked if I could have a syringe with a needle to use for injecting light machine oil into small bearings in small motors or mechanisms. While several of the medical personnel thought it was a legitimate request, I never received one. So, I use the much larger needle on my Radio Shack “fine point” oiler, but it usually leaves a mess.

      1. Next time you go to the pharmacy, just tell the pharmacist that you’d like to purchase a few empty syringes. I’m sure he/she will ask you why, but they’d be interested to hear of this application and I’m sure it would make for a fascinating conversation. A buddy of mine used to do that when he’d refill inkjet cartridges… the syringe tip made the process much cleaner than the larger blunt tip that would come with the refill kits. He’d buy the syringes in batches of ten and I think he paid less than $5 for a batch. Several tip diameters to pick from too.

      2. I had a similar issue several months back where i needed a syringe to inject a lite fluid for some acrylic work. I live in a moderetly dodgy area and got some very unusal looks from the chemists when i asked them for a syringe and needle greater than 22 gauge.

        After getting turned away three times i found one chemist who begrudgingly sold me a “sterifit” pack that was specifically target at drug abuses, it even had the witty line of “a fresh fit for every hit”.

        So they are definatly availabe you just need to swallow a little pride and embrace your inner drug abuser.

      1. It’s not like they conduct an intake questionnaire when you go to get the free needles. If you ask, they give. Just go to your local needle exchange and ask if they have a fresh one for you.

      2. @Ren: You can though. If you are in the US, syringes do not need a prescription no matter what some random pharmacist may tell you. I had to argue with them only once about it when I was uninsured and going to college. I’m a type 1 diabetic and use a pump now, but when I was on injections, I’ve stopped at random pharmacies when on the road or because I forgot or ran out syringes that day. Most sell syringes in a box of 100, but will also sell the individual packages of 10 inside the box. It’s usually not more than a couple dollars for 10 syringes(1/4 to 1/2 CC anyways, never needed bigger ones).

    3. Just run on down to your local farm supply store. Some of you may have to drive a bit but probably not far. They have a wide variety of syringes available no prescription needed. Nothing as small as a ultra fine diabetes needle but some pretty small ones. If you need one thst small just ask around. There are a lot of diabetics out there.

  2. I don’t know what the process is where you live, but where I am they record your name when you get syringes from the pharmacy. I don’t know if you need a prescription (I had one, but I don’t know if it’s necessary). I didn’t technically have to sign for them, but the transaction was logged.

  3. There are some states of the US where you do need a prescription to buy needles (even though it doesn’t make sense). However, you can get them by mail from veterinary supply companies.

  4. If you go to the pharmacy in my city they will sell you syringes at outrageous prices, because there is a drug problem. Smart idea, so people won’t waste them and use them only once… *fp*

  5. That is a great idea.

    I have bought syringes for years. Usually the small insulin ones, but also larger ones for epoxy, etc. Never have I been asked what for (though for the large ones, I asked for recs on size for thick glue, etc).

    It’s so handy having them around for projects. Some I fill with oil, others glue, grease, flux, etc.

  6. I use brain needles myself…just the needles themselves; they are very thin and pointy. There are two ends to them…a short and a long. I file the point off the short end and can then just clamp a probe on. I tried wrapping wire and soldering, but wrapped wire tends to be unreliable and solder just won’t stick to them. As for resistance, it seems to be minimal…two clamped-on needles touching each other read as a little over 1 ohm, and that’s about the same as two of the clamps touching each other. I wouldn’t know about the difficulty in getting them; I got a free mini-fridge from a lab that was closing down and it came with lots of them, plus lots of other medical equipment ideal for doing experiments on small, defenseless creatures.

    Oh, and there are two other handy little uses I found…if you have to open up a hole in a PCB that has been previously soldered and you don’t have room to use traditional methods, you can touch the iron to melt the solder, then stick the needle in and wiggle it around quickly until the solder hardens. This leaves a nice hole with no worries of de-soldering nearby SMD parts, and without fear of lifting traces on cheaply made boards. Other items can be used for this, but as I said, solder just won’t stick to them! The other use? Holding SMD resistors and caps in place while soldering. Again, solder won’t stick to them, no matter how hard I try, no matter what mix I use. The flux residue does, but the solder does not.

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