USB Tester




About: Robots and video games...

This simple device allows you to check the correct working of the USB ports of any computer, using a green led and message from your operative system.
It will allow you to test the proper assembly of any port without risking any expensive device.
If you normally work fixing computers this is a must in your tool kit.

Ps: I'm from Argentina so let me know any grammar mistake

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Step 1: The Circuit

The circuit is very simple using only some discrete components.
The operation is simple, you connect it to the USB port, if it's okay, the green LED is lit in all its intensity and you will have a message from your operative system telling you than a USB device has been detected. If the polarity is reversed the red LED is lit in all its intensity. Any other combination causes lit one of the two LED but very dim.

You will need:
The PCB (see step 2)
The USB connector (see step 3)
Two 22K resistors
One 1k resistor
One 100 ohm resistor
One 1.5 k resistor
One 3v3 zener diode
One 1N4148 diode
Two leds (green and red)

The diagram was extracted from this forum (in Spanish):

Step 2: The Board

The PCB is very small and simple.
I made it using the method of ironing.
PDF file annexed contains the design ready for printing.

Step 3: The Connector

This project seeks to be economical so you're not going to buy a connector. We will recycle a cable that does not work.
First we remove the plastic guard with a knife.
Then remove the remains of cable and solder it new terminals.
Finally I soldered two terminals to the metallic body to keep it firmly attached to the PCB:

Step 4: Soldering Components

The components are easy to weld.
Try not to overheat the diodes and not allow shorts in the PCB.
Use the second image as an assembly guide.

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    83 Discussions


    3 years ago

    Clever hack!


    3 years ago

    Great project! Very useful. This is just what I needed. Thanks!

    Hey Bruno, thanks for sharing, this is exactly what I was looking for. I'm planning to use a bicolor led, the one which turns green or red depending which way the current flows. anyways, I'm from argentina too, and I have a small grammar correction for you, "Try not to overheat the diodes and not allow shorts in the PCB." should say : "Try to not overheat the diodes and don't (or do not) allow any shorts in the PCB" brunoip, you are legendary , here in Argentina. also se dice easy to solder, weld is for big uniones.


    Reply 4 years ago on Step 2

    Thank you Brunoip. I made mine on a breadboard. Seems to work work fine although I only had 15k resistors on hand not the 22k you had specified. Need you to design one for testing a USB 3.0 port now. :-)


    6 years ago on Step 4

    Can anyone please tell me the working principle of this USB tester


    6 years ago on Introduction

    sir laptop got like this hhh

    panic modem1s73r

    Reply 6 years ago on Introduction

    Q: "When does the red LED light up?"

    A: when USB polarity is reversed. this little mistake can easily be done on auxiliary or remote ports on desktops. those are ones that connect to motherboard through cable, for example:

    plugging in camera or phone etc is an expensive way to test for this.


    9 years ago on Introduction

    What wattage resistors are you using, or does it make a difference?

    I'm new to building electronic devices, and thought this would be a good one to try. When I went to get the supplies from my local store the first question they asked was what wattage. I bought 1/4 watt ressistors assuming that the voltage of a usb port is around 3.3 volts.

    Thank you for the project and any help you can give.

    2 replies

    Reply 8 years ago on Introduction

    I believe they are 1/8W as they are the same size as a 1N4148 diode.


    Wattage(sounds like cabbage, haha) doesn't really make a difference. In this case, seeing as you're using an USB port, with 1/8 you're more than fine. BTW USB uses 5 volts DC, usually @ 200-450 mAh.


    8 years ago on Introduction

    your schematic is cool
    here is a perfect solution for you