DIY Ethernet RJ-45 UTP Cable Tester UltraCheap (Wall Mountable)




Hi Guys EnergyTR is Again With you.

 We are going to make DIY RJ45 Cable tester for incredible cheap.As you know cable testers are really expensive insturments and for people who always works with network it is an essential part.
I will try to help you to build one of them with basic electronic ways.

 We will use basic components and methods.The components is going to be easly find in electronic stores.

 Ok Here we go Have Fun.

 Special Thanks For Mrs.Patricia Zugg
 And All Cisco Networking Academy Class & My Classmates
 Greetings From Alaska To TURKEY


Step 1: What We'll Need ? Scheme

As i said this DIY project is from very basic components which you can easly find from all electronic store etc.

---How is it work ?----
Basicaly 2 connectors are directly connected to battery and leds but they are not connected to each other so we will use UTP cable as a bridge of RJ45 connectors.So if any of Leds are not working that means our UTP cable is not working properly on that Leds so we can troubleshoot on our cable.

  I will give the list in 2 parts first  is equipments and 2nd is components.

PunchDown tool
Soldering Iron
Cable Cutter

LED's x8
UTP Cat5 Cable (20cm)
9v Battery
9v Battery Clip
Wall Mount Box
Cat5 RJ45 Female Jack x2
Resistor 220ohm
Female RJ45 Mount Plate

So now we good to go Lets Begin...

Step 2: Lets Punch Some Cable !!!

Ok here we go;

* First step is cutting the UTP cable from middle.Like 10 cm is going to be Ok.

* When you cut the Cable from the middle take one of em and cut the covers like 2-3 cm from each side.

* Now you will see the cables will be together you need to seperate them

* You do not need to cut the heads of the cables punch down tool will do that job for us.
* Go ahead and take the cover of the RJ45 Female connector

* As you can see there is colors which indicates the proper location of the cables

* Omg same colors with cables which we cut before :)

* Now locate them in proper location you may want to use screwdriver to keep them harder because they always try to go off

* In that part you will punch some cable This part is the most important and the may be only risky part of our project.The biggest fault in the punch down tool usage is cutter site.Punch down tools mouth has 2 sides 1 of them should be Cutter im sure your tool will indicate clearly too.What we are going to do is we will locate our punch down upon the cable but be sure


in order not to cut connection between cable and connector.When you all done be sure there is no cable/s hanging sideways of the connector.If there is some cut them manually

*We are done with first connector.

   REMINDER : You will need the same thing 2 times so to other connector you may continue the ways again.

Step 3: Make Some Soldering

Now we will do our small soldering mission

 * First of all we need to cut the tips of the cables of our connector which we finished.

*When you cut the tips be sure all in the same lenght because what we want to do is we will connect them each other.

*As i said connect 8 cables to each other and check they all touching anycable.

*Now  take your soldering iron and solder the resistor to 8 cables which we connected.

*When your job is done take your 9v Battery clip and solder the positive(+) side to end of the resistor.Dont worry about the negative(-) side because we will use it later.

Step 4: Holes to Plate

In that step we will drill some holes to our plate

 I cant give any exact number of drill head it will depend on your size of LED what i did is just i take the LED and tried to match the drill heads from backwards with my eyes.But becareful because you dont want to make bigger holes then LED.They will come lose and if you dont glue them they will fell down into box.

Step 5: Place the LEDs to Plate

   Now we will place our LEDs to holes which we drilled at 4th step.I used green and red LEDs and i placed them as 1 green 1 red but its your call.Only important part of that step is just be sure negative(-) legs of the LEDs should be the same way inside or outside.They all needs to be paralel to each other.(Check images you will understand what i am sayin')

Step 6: Soldering the LEDs and All Connections Together

Semi Step 1

***When you finished to placing the LEDs what you want to do is stretching the negative (-) legs of the LEDs to each other but in order.Like in the pictures just patch them to lower another LED.And After you finished you must have only 1 enterance for negative legs.Solder all of em together.

Semi Step 2

****Take your RJ45 connection which without resistor and battery clip.And take the whole cover from on it.

*Take the tips of the cables

*Place the connector to the hole on the Plate

*And In order solder them to positive leg of the LED which you want to pick.But be sure you did in order. For example "  Top left LED indicates BlueWhite on UTP cable" with that way you can test your RJ45 cables which cable is not working or working properly.

Semi Step 3

****Take your first RJ45 connector which with resistor and battery clip . As you remember we left negative leg of battery clip free.So now we will solder it to shared negative leg of the LEDs thats why we connected them each other.Now you can easly solder negatives together.

*Place the RJ45 To other hole on the plate.

Step 7: Final Touch and Testing

There we are last step

*Now plug the battery to battery clip.

*Take a RJ45 Lan cable which you are using on your internet or anything else but which you dont need to test and plug to connectors.2 sides of the Cable should be pluged in Tester in order to test (im sorry i need to say that much basic ) so if your all leds are shining then you did a good job your soldering and other things are fine now you can go to other step

*If its not be sure all soldering are done well

*My suggestion is use hot glue to prevent touching legs each other.

*Now you can place your Plate to your wallmounth box.

*Only thing is screw the top and bottom and You are done.


Take cable which you want to test and plug both sides thats all you need to do.If some LEDs are not working check which cable color are they indicating and solve the problem of your cable.

Waiting For your Comments...

3 People Made This Project!


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51 Discussions


7 years ago on Introduction

Thanks for this project posting. I took a look at your project and all of the comments from others as well and thought I would take a crack at building it. During the build, I took some liberties to implement a few of the comments as well and the result was a hybrid from your design.

I added some complexity, but hopefully some utility and capacity as well.

My final product was a tester that can test individual lines, can also test when only one end of the cable can be brought to the tester (or tester to it), and can identify if the cable under test is a standard or a cross over cable.

Ending project cost is about $30 so not as inexpensive, but does what the commercial tester I found for $50 does. Like yours, it doesn't do signal quality, for that commercial testers charge about $100. I found it better built (solid) and at least a lot more fun than the cheap (my opinion junk) $15-$20 testers on the market.

check it out at

Thanks again to energytr for the inspiration.

1 reply

Reply 2 years ago

Are you still alive? I can see these posts are 5 years old =D But your instructable is no longer available and I'm looking forward to build something exactly like it. Do you mind bring it up again? Thanks anyway.


2 years ago

yeah it's alright, looks a bit cleaner than mine ;)


6 years ago on Introduction

thx for sharing and I recommend you a website for

]glow in dark tape


6 years ago on Introduction

I really love this post and thank u for sharing your idea .by the way, I give you glow in dark tape


7 years ago on Introduction

This will work finefor a cross over cable, it is just that once you note a non-conduting path, you have to realize that the LED coresponds to the correct line (LED 1 = pin 1, LED 2 = pin 2 etc.) on only one end of the cable (the end that is plugged into the socket wired to the LED's. The other end of the cable will not be on the same pin because the wires "cross over" to another pin in the other socket. Not hard to figure out. (1 - use a crossover wiring matrix to know the "other" end corresponding wire. or (2- Test the wire once and note the LED that isn't lit, then switch the ends of the cable and note what LED now doesn't light and that will be the other ends corrsponding pin.

Remember the limits of this type of testing. It is for continuity only (tests for open / broken wires in the cabe). It cannot test for shorts (signals that can cross wires because they incorrectly conduct between each other) or for issues of impedence, cross-talk, or other poor signal quality that can effect network performance.

1 reply

Reply 7 years ago on Introduction

But then again, your cheap $10 - $20 purchased testers have the same limits, they are continuity testers. You have to spend closer to $50 or more to get a tester that looks for network performance issues on a cable under test.


7 years ago on Introduction

keep in mind this wont work for a X-Over cable cause of how you initially wired the project up...just a thought in hopes of inspiring a way to incorperate an option to test X-Over cables for connectivity.

2 replies

Reply 7 years ago on Introduction

This is obvious that it you wont get a decision whether the cable straight thru or x-over, But it definelty tests out X-Over Cables as well, in basics despite the fact X-Over cable are Crossed between Tx and RX on both sides still all cables are in use therefore you will be able to understand if led is lighting up or not, And by looking pyhsically, you'll decide if its Correctly Crossed ;) Im sorry that i couldn't Make it perfect but its cheap as it is and im still using this stuff in my Cisco Lab. Thanks for comment =)


Reply 7 years ago on Introduction

hahaha, woah now i never said that it has to be expensive to be worth making...and something being cheap isnt a bad thing either.


7 years ago on Introduction

So the 9 volt drives all the LEDS without a probelm, even though the schematic says 12?


8 years ago on Step 7

Really great job my friend! 1 question does it really light up all the leds? I only see 1 or 2 on.


8 years ago on Introduction

Deja vu! Long ago (almost 10 yr ago), I did a very similar tester, even the box is also blue, I never published it until recently. The biggest difference is that mine got a microcontroller that adds some convenient features but make it harder to build than yours. If you wish to have a look, the link to it is: 


9 years ago on Introduction

If you have the parts laying around this is a great project.  I get the thrill of making my own gear, but only if the cost is acceptable.  Going to a local home center the faceplate and sockets alone will run about $10 US.  Testers can be found online for less than $5 US.

I'm not knocking the instructable (its nicely made), but just letting those who may be interested in testers that there are cheaper options.

1 reply

Reply 9 years ago on Introduction

I have a 8 wire that tests each wire one at a time and indicates mismatched wire patterns. 1-8

I also have a 4 pair tester that indicates at a pair level 1,2     3,6     4,5     7,8

Then there is the Fluke, this will show me the entire wire map and where the break in the wire is at in the cable. (with in a foot)

Nicely done though for some one that just needs to make sure the patch cord is good.


9 years ago on Introduction

 If you wanted to put in an on/off switch, so you would have to take the battery out after every use, what side would it be on red or black?

1 reply

Reply 9 years ago on Introduction

You wont need any kind of on/off switch. Thats Because the is no current between + and - sides of the battery unless you plug your RJ-45 Cable to test. This box basically works the idea of completing the circuit with ethernet cable or the cable you would like to test.I mean your on/off switch is your cable..