RJ-45 Key Chain and Rack




This Instructable will show you how to make a cool colorful key chain and a rack for storing those key chains out of RJ-45 jacks and plugs.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Materials

there are two parts to this instructable.
the first part is the key chain, in order to make the key chain you will need the following:

1. RJ-45 plug crimper
2. cutting or sleeving tool
3. scissors

1. 2 pair or more network cable
2. RJ-45 plugs (male)
3. colored rubber protector for RJ-45 plug
4. key ring

the second part is the rack for the key chain. it is optional. in order to make the rack you will need the following:

1. depending on the type of wall and the type of mount.

materials : 
1. wall mounted box for RJ-45 jacks
2. RJ-45 jacks (female)

Step 2: Key Chain Step 1 : Disassembling and Cutting the Cable

the standard network cable consist of multiple parts, the only two parts we will be using are the insulation and the wires (4 wires to be exact).

disassemble the cable, identify the parts and keep the parts mentioned above.

the minimum length of cable we can use is 10cm because that gives a little tail popping out of the rubber protection. you may use more if you want a longer tail.

choose the color of wires you want and cut them to the desired length.

Step 3: Key Chain Step 2 : Final Preparations and Assembly

take the 4 wires and fold them down the middle to form a U shape.

order the colored wires however you like.

using a pair of scissors cut the tip of the wires in a straight line.

gently insert the wires into the RJ-45 plug. be careful not to mess up the order.

while holding the wires in and making sure they reach the very end of the plug crimp the plug using the crimping tool.

check the wires are in place and not coming out.

cut about 3cm of insulation and insert the folded wires into it, then push it as far as it will go into the plug.

put the rubber protection over the wires and plug.

insert the key ring into the loop created by the folded wires.

Step 4: Rack Step 1 : Assembly

well, this part is pretty straight forward.

most wall mounts will include the RJ-45 jacks built-in, if not just put them in yourself - its just a couple of clicks.

make sure the jack is sturdy enough. the jack will get connected and disconnected many times, this is not regular use, regularly you would connect a cable once or twice in a relatively long period of time.

mount the box(es) on the wall.

Step 5: Final Thoughts

i recommend tagging the ports so you know which key goes where
you can also use flags to tag the keys
if you have different colored rubber protectors you could color-code the keys and divide them into groups by type or location of the lock they open.


3 People Made This Project!


  • Book Character Costume Challenge

    Book Character Costume Challenge
  • Made with Math Contest

    Made with Math Contest
  • Cardboard Speed Challenge

    Cardboard Speed Challenge

57 Discussions


2 years ago

linus from LTT has this but with an actual working Switch!


7 years ago on Step 5

This is an excellent idea! I don't have a great place to mount the jacks, so I think I'm going to mount an old router or switch in my free-standing coat closet and plug my keys into it instead. I'll upload an image when I get it finished. Very cool.


7 years ago on Introduction

I love this idea. It give life to keys and dead networking equipment :)


8 years ago on Introduction

Here's my version.... was a junky 12 port patchpanel surplus from a refit at a small site. Each socket is wired as an ethernet crossover, just cos.

I thought of using a unique crossover pattern to light up an LED if the wrong plug is put in a hole, but never took it further.

We also had an ancient managed 10 Mbit switch which would have done SNMP traps every time a link went up or down. However it was too power thirsty to actually use for such a frivolous purpose.

8 replies

Reply 7 years ago on Introduction

well I haven't done that yet, but I would use something like 1-8, 2-8, 3-8 etc up to 7-8, then 1-7, 2-7, 3-7,...6-7 etc Missing out 8-7 because its the same as 7-8.

So you could have 7+6+5+4+3+2+1 combinations or 28 in total.

Might need to get creative, if you want a red and green LED so that a wrong plug lights a red and the right plug lights a green LED.


Reply 7 years ago on Introduction

actually you can get 56 combinations from your configuration because 7-8 is not the same as 8-7, this is why:
an LED is a diode, it allows current flow in one direction only. which means you can use each combination with inverted polarities to give you double the combinations. for example, if 7 i connected to GND and 8 is connected to +V, an LED with the anode connected to 8 and cathode connected to 7 will light up but an LED with the anode connected to 7 and the cathode connected to 8 will not light up, thus giving you double the combinations.

if you want to use 2 LEDs, you can get 14 combinations:
lets say you connect the LEDs to pin 1 and 4, pin 1 will be connected to GND and pin 4 to +v, all other pins will be connected to -V, for this to work you will need 2 LEDs connected in parallel with different polarities (green has cathode connected to 1 and red has anode connected to 1).
what this means is that when connected to the correct port, the green LED will light up because its anode is connected to +v and catode is connected to GND, the red LED will not light up because its catode is connected to +v and anode is connected to GND (which creates current flow in the wrong direction). whan connected to the wrong port, the +v pin is not aligned the LEDs pin causing the LEDs pin to connect to -V. the red LED will light up because its anode is connected to GND and catode is connected to -V (current flow is from GND to -V, as opposed to +v and GND where the current flows from +v to GND), the green LED will not light up because of the same reason as before.
for this to work you will need a common GND pin for all combinations, this will give you 7 combinations and if you invert the polarities on the LEDs and on the circuit (+v and -V) you get 14 combinations.

i haven't figured out how to use dual-colored LEDs yet.
you could also use a microcontroller like an arduino to trigger an alarm or display a number or text on an LCD for each plug or even report to Twitter.


Reply 7 years ago on Introduction

Good thinking - except for the twitter part. I see no reason to tell the world that you just took your car and house key out. Kinda says "I'm out of my house for a bit - come rob me."

On reflection, 7-8 IS the same as 8-7 because its only wire in the plug. You're talking about putting the LED in the plug, which was not part of my design. I intended on putting the LED above the socket, so its permanently wired into the wall panels.


Reply 7 years ago on Introduction

you're right on all parts.

it doesn't have to update your twitter account and it doesn't have to say anything revealing, it can report to it's own account just for your remote monitoring. kinda like the twitter-reporting-roomba - who cares when roomba finishes cleaning your bedroom?! you do.
and it was just an example of the marvelous things you can do with a simple microcontroller.

you're thinking of using the plug as a jumper, in that case, 7-8 is the same as 8-7.
what you can do to have the best of both worlds is to connect a simple diode between the pins. that way you get a polarized jumper that will only light an LED with the right orientation - giving you twice the combinations with socket mounted LEDs.

another thing you can do is not use a common pin on the LEDs (like your initial design implies) and use 2 jumpers inside the plug, giving you more combinations, if you implement the first idea of a polarized jumper (you can use one diode on one jumper, no need for two) you get, once again, twice the combinations.

i only see one problem with using the plug as a jumper - you can only connect one (or two) wire(s) inside the plug, meaning there are only one or two wires in the loop that hold the key. i think that will be a little flimsy, unless you use some CAT7 wires or something.

i think i'll revisit this instructable and try making this work. (just received 1000 green LED in the mail this week, time to put them to good use :) )
hope i'll find the time...


Reply 7 years ago on Introduction

i will be super if i get a instruction wihich colore in which area i have to put..:D


Reply 7 years ago on Introduction

the colors don't mater, you just need to close each circuit using different pins.


7 years ago on Introduction

I should do this. The wife might not like it so much.

I do think that I like the idea of using a burnt out router to plug in with.

Hi Harari!

Absolutely LOVED this instructable!!!! So much that I decided to feature it on my website. You can see the page here:
If, for any reason, you do not wish to appear on my website, just let me know and I'll remove my post right away.


1 reply

8 years ago on Introduction

ThinkGeek already has something like this for the keychain part.

Different color coded versions.

Other sources too, such as


If desired you could replace the chain with a metal loop.

Rollover Adapter.jpg
1 reply

Reply 8 years ago on Introduction

I've never seen these articles or anything resembling this anywhere.

I'm proud to say this is 100% my idea.


8 years ago on Introduction

This is a great idea. I'll have to try it out.

A suggestion for the wall hanging part is to use the ports from old/dead hubs, switches or routers. You could remove the port groups from the circuit board and put them in a custom case. Most hubs/switches have clusters of 4 or 6 ports that could be arranged in various ways to provide spots for countless keys.

Thanks for the inspiration.


8 years ago on Step 3

I do a lot of cable termination, and have fell in love with the EZ-RJ45 plugs from MilesTek. lets you feed the wires through the plug and crimp and trim in one go!
I've got some leftovers from a recent project, I'll definitely need a key fob like this!


8 years ago on Step 5

This is a fun idea. 
Why not make these useful loopback plugs?

You could store them plugged into the switch, and your syslog would tell you when they've been removed and returned!

OK, that's a bit crazy, but why not wire them in a meaningful configuration while you're building.

Ethernet Loopback
Pin <-> Pin

T-1/E-1 Loopback