Inline Cylindrical Fuse Holder (Connectors)

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Introduction: Inline Cylindrical Fuse Holder (Connectors)

About: As a soon to be senior in high school, I keep myself busy with hands on projects.

This instructable is for the cylindrical glass fuse holders created on TinkerCAD. This project was started in June and entered into the TinkerCAD design competition. There are two types of fuse holders, one for the common 5x20mm and another for the 6x30mm. This instructable is divided into 2 parts. Steps 1-8 explain how you can use the fuse holder. If you interested Steps 9-15 details the creation of the fuse holder.

This design is used for connecting cylindrical glass fuses to electrical circuits/devices.

This is the link to the design files: https://www.tinkercad.com/things/2BvURwIvokj

Step 1: The Fuse Usage: Requirements

As a disclaimer, these fuse holders are not certified by any organizations to meet safety standards. Therefore, use these designs at your own risk. Remember, there are certified high quality fuse holders available online or at electronics stores for a few bucks.

I recommend PETG or ABS, as they can resist higher temperatures. Only use PLA if you are sure the temperatures will not cause the PLA to warp/melt and potentially cause short circuits and other hazardous situations.

Also, small nails or pins will be required to construct the contact points on the fuse.

Finally, you will need a decent printer, that can print threaded objects. For example, my Creality Ender 5 worked for me.

Step 2: Choosing the Fuse Holder

First, choose which fuse design you want. There are two sizes: 5x20mm and 6x30mm. These designs will not work for other sizes without serious editing as parts are not scalable.

Next, choose which style you want. There are two styles, simple or mountable. The simple style holds the fuse while the mountable fuse allows the fuse to be easily attached to a flat surface while still allowing easy access of the fuse.

The stl files have been attached below, although I recommend getting the file from TinkerCAD so you will be able to edit it with TinkerCAD easily. (Here is the link to the TinkerCAD design page: https://www.tinkercad.com/things/2BvURwIvokj).

Step 3: Choose Your Fuse Contacts

To make a electrical connection with the fuse you will need two small nails to contact both sides of the fuse. The nail head diameter must be smaller than 6mm for the 30x6mm fuse holder, or 5mm for the 20x5mm fuse holder, and should be larger than 1mm. Also, make sure that the nail conducts electricity, as some are pretreated with a non-conductive coating that must be sanded off.

I cut the two nails to be about 1cm long, although longer wouldn't hurt.

Tip: you could possibly use another item or method to contact the fuse, such as aluminum foil or a bent wire.

Note: Copper nails would be optimal, aluminum would work (but it is hard to solder to aluminum), common steel nails are fine. In the end, they all work great in terms of conductivity.

Step 4: Adjust the Design

To make the nail fit, we need to edit the design files. To do this adjust the center hole size to fit the shaft of the nail. Aim for a snug fit and adjust accordingly to you printer's tolerances. You can always glue the nail in place if the hole is not 100% accurate.

For the fuse holder cap, ungroup, adjust the hole size, align to center, and regroup.

Do the same for the body of the holder.

Basically, adjust the hole size for the nail, recenter, then regroup.

You do not necessarily need to edit the design. Instead, a drill could be used to get the proper size. The default hole size is for 1.75mm shafts.

Step 5: Print It

Next, export the object and print the model using your filament profile. No supports are necessary if oriented correctly.

I printed at 0.2mm at 50m/sec.

If prints come out stringy, try printing only one object at a time. Also, enable combing.

Step 6: Processing

After printing, check the fit. Sometimes the threads are a little tight and must be screwed on and off to loosen it up. It should be hand tightenable afterwards. Check the fuse for fit.

Step 7: Assembly

To assemble, insert the nails through the holes in the fuse holder. The shaft should be sticking out. Glue in place if necessary.

Solder/crimp wire to the fuse holder's contacts to connect the fuse to circuit. Also, to prevent oxidization, tin the nail heads with solder.

Insert fuse and screw on cap. These fuses are glass so do not over-tighten. The view hole on the side can be used to ensure proper contact. THE CAP DOES NOT NEED TO BE SCREW ON ALL THE WAY.

If the fuse holder is mountable, screw in or glue in the mounting plate to a flat surface. Then you can snap in the fuse. If the fuse holder does not snap in place you may need to sand some things down.

Hint: If the fuse holder is installed along a wire rotate the cap counter clockwise a few times before screwing on clockwise to reduce stress on wire.

That's all. The fuse holder is finished.

Step 8: Modifications

To make the fuse more secure, you could add a spring. This ensures a better contact which should allow for higher current draw and also increases vibration resistance. This modification is pretty simple as it only requires a pen spring.

Cut the spring to about 4mm to 7mm or a 1/4 inch. Then use a needle nose pliers to bend the ends inward (to ensure good contact with the nail and fuse). Insert spring and fuse. Then screw the cap on. As the compressed spring takes up space, the cap will be screwed in less.

Note: This may not work as well for the 6x30mm fuse holder as the spring may be to thin.

Step 9: How I Made the Fuse Holder

Next, we move on to the creation of the fuse holder.

This design was created for a project I was working on. In the middle of June, I realized I should probably connect a fuse to a AC power inverter for one of my projects. Since I already had the properly rated fuse, I needed a way to mount it. So I needed to find a fuse holder file to print. It turns out that there was no pre-made fuse holders for glass fuses on various websites (TinkerCAD,Thingiverse), so I had to make one.

Step 10: What I Wanted

Next I laid out the goals for the build.

I wanted it to be:

  • Fully Enclosed for safety
  • Printable without supports
  • Fuse should be easy to change
  • Minimal required supplies
  • Mountable

Step 11: Creating the Design

With these goals in mind I set out to create the design. As I had no reference product to mimic, I had to create one from scratch. This is a good way for me to use a lot of plastic. The first design I tried failed but my second design showed promise. I settled for a screw-to-tighten design, which was interesting as I have never tried to create 3D printable threads ("Screw Threads" under "All Shape Generators" made it possible).

Step 12: Testing the Design

Next, I ran the design through some tests. I had some trouble getting the threads to the right tolerances and tried a few iterations. Also, I had to design the mountable fuse holder that would snap in the mounting bracket. After that, I installed the two nails and put in the fuse.

Step 13: Using the Fuse Holder

Since I was going to use the fuse holder for a project, I had to install it. After soldering the fuse holder to the correct wires and ensuring proper connection, I tested the AC inverter, which worked. Now the AC inverter has a fail-safe in case something malfunctions.

Step 14: Making One for 5x20mm Fuses

Since the cylindrical glass fuse I used was 6x30mm, I decided to make one for the more common 5x20mm fuse. I had a few 5x20mm fuses laying around and a design that worked with the 5x20mm would be nice.

Since the fuse holder cannot simply scale down I redesigned the mounting bracket and re-tuned the thread tolerances to make it work. This took a few tries, and I broke a fuse during testing, but I finally got the design to work.

Step 15: Entering the Contest

After I got the several variations to work, I cleaned up the file and rearranged the objects so it would be easier to use. After that, I published it on TinkerCAD (Here is the link: https://www.tinkercad.com/things/2BvURwIvokj). Then I wrote the instructable. Even though it was the first time writing an instructable, making one was straightforward. Hopefully, this project will be helpful and useful to others.

Some may be wondering why this was entered into the "Connectors" category. There are several reasons.

First, this project does not fit that well into other categories. Although there are moving parts, they are only present in small parts of the design. Even though I used it to "upgrade" a circuit, I had added other sizes to the design and also gave detailed instructions on how to use it.

The "Connectors" category worked best as the fuse holder cap screws on and the mounting bracket design snaps in place. Finally, the fuse holder allows one to connect a fuse to a circuit.

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    8 Comments

    0
    CrazyBlackStone
    CrazyBlackStone

    Tip 1 year ago

    Hi, I like the idea of this very much. It is very creative and useful; however, I'd like to express some safety concerns.
    If I understood the design correctly (sorry if I didn't, it's late at night), you use the heads of the nails for making contact with the fuses and then solder the wires to the ends of the nails. The commonly used types of nails are usually made of steel, which is very prone to oxidation. Once the oxide layer builds up, the resistance can become very high and start to be a problem. Also, steel is not known for being the most conductive material.

    I'd recommend that you use copper nails instead of steel and sand down the surface of the copper nail with a fine grit sandpaper. Then apply a tinning bath to the nail to stop any new oxidation from occurring. Or alternatively aluminum nails would work too if you can find them.

    Just my suggestions. Best of luck to you from a fellow contestant to the design contest. :)

    0
    File13
    File13

    Reply 12 months ago

    Thanks for bringing this to my attention.
    Yes, the nails make contact with the fuse. Also, steel easily oxidizes, if exposed to oxygen and water. But, if there is minimal water present, oxidation will be minimal. As the contact points on the nail head and the fuse are forced together, this should also decrease the oxidization on the nails. As long as the fuse holder is not in very wet environments, it shouldn't effect the performance of the fuse.
    Steel also has a much higher resistance than copper. But stainless steel, which is commonly used as the contacts in commercially available fuse holders, has a greater resistance than steel. We can then extrapolate that the resistance of the steel nails should be okay (as long as oxidization is not present).
    I like the tinning idea as this would remove any oxidization problems.
    Thanks for the suggestions and good luck!

    0
    CrazyBlackStone
    CrazyBlackStone

    Reply 12 months ago

    Hi, after doing a little bit of digging, I agree with you.
    Bolt-down chassis mount commercial fuse holders do often use nickle/zinc plated steel for the contacts and those are often rated for quite a high current (100A), and plus those puny little glass fuses can't take more than 20A anyways. Smaller PCB mount fuse holders all use brass or tinned copper because they need to get the resistance low in a small amount of space.
    I did the resistance calculations and it seems that the resistance for a 2d size nail cut to 12mm length is only around 0.11306milliohm, so it'd be more than well within the resistance limit for this application.

    I think you did an amazing job on this project and I hope that you win first place in connectors :)

    0
    File13
    File13

    Reply 12 months ago

    Thanks, always nice to have someone do the math.
    Also, excellent job on your project. It is very advanced and well documented. You must have had to do a lot of testing :D

    0
    luklev
    luklev

    Tip 1 year ago

    This is quite an interesting idea.
    The only concern I have is whether the contact of the nail with the fuse is stable enough, in terms of mechanical vibrations, and also whether the transient resistance is small enough (current concerns). The connectors in the fuse holders usually hold the fuse around the terminals and, in addition, are pressed by some flexible mechanism from the sides.


    I would stuff the nail inside the holder through a small spring (eg from a pen) and thus partially solve the mentioned problems.

    But overall, I really like it and it's nicely documented - you have my vote!
    0
    File13
    File13

    Reply 1 year ago

    Yes, a good connection was something I was worried about. For low current, it seems to work fine as I think the cap applies some compression to the fuse. If the current is higher then it should probably have a better connection, which a simple spring could easily fix.
    Thanks for the tip!

    0
    seamster
    seamster

    1 year ago

    This is very nicely put together - well done! : )

    0
    File13
    File13

    Reply 1 year ago

    Thanks! it was fun and kept me busy.