Djo Labs

Simple electronics for Fun !

New Website

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Hi everyone ! With a little bit of delay, my new website is finally online !
You will find here a very small selection of electronic stuff I made for Fun. Most of the time It's useless, but hey...It's fun !!!

As you can see, I choose to write my Website entierely in English (I'm French !) because I want it to be readable by the most people as possible, all over the planet !!

I have a lot of nice little projects to come but I don't have the time to put all online, so stay tuned !

Don't forget that there are two pages in this section ! (Go to page 2)

24V LED Strip on 230Vac

Here is a simple way to connect some 24V LED Strip on 230Vac to make a little decorative lamp.

Don't do it if you're not familiar to mains voltage, It's dangerous !

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Here is the schematics, as you cans see, no rocket science here !
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But if you build it, put it in a safe transparent box (I used some plexiglass for safety and style !)
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Hardware Secure USB flash drive

Recently, I was bored on a slow weekend, so I made something just for fun ! It's called an Hardware "Secure" USB flash drive.

Well, in fact, It's not very secure, but you need to know the right switch combinaison in order to acces the disk drive. Nobody will be able to see your secret files !

The trick is to use a bunch of switches to power the USB 5V only if the combinaison is correct. No software, no drivers, universally compatible !

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And It looks just nice in a small metal box !
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Grid monitor

Recently, the high temperatures caused a big power outage in my region, leaving a geek in the dark ;-), so I decided to build something that could help me to predict a risk of grid overload !

Our mains grid is running at an average frequency of 50 Hz, but if the grid becomes overloaded (too many air conditionners running on a hot day), the frequency can slightly drop because the geneators slows down. If the frequency drops below 49.8 Hz, the grid can offload certain regions to avoid a general failure.
You can have more informations on

This circuit measures the average mains frequency (between 49.8 Hz and 50.1 Hz) using an Arduino nano, and displays it on seven LEDs, easy to read.
So the row of LEDs shows the instant load of the national grid.

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Here is the circuit diagram, it uses a transformerless power supply, bear in mind that the mains voltage is everywhere on the circuit (including the LEDs), so be VERY carefull and NEVER EVER plug the circuit to mains while programming the arduino (via USB)...
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The code is on my other computer but it will be here soon...

Simple TV Ambilight

Several years ago, Phillips introduced the "Ambilight" wich consist to light the wall behind your TV with a color corresponding to the picture displayed to the screen. This makes a mood lighting behind the TV that looks nice and limit eye strain.

Some other people developped the same thing for fun. They usually sample the RGB signals directy on the video cable to drive LEDs (with some processing).

In this circuit, I choose not to sample the video cable but, instead, to sample the amount of light (from the three colors components) coming from the screen.

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Here is the circuit diagram, as you can see, It's very simple...
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The light color sensor is made of three light dependant resistors (LDR) painted in Red, Green, Blue (using white board color pens).
This opamp circuit converts the average color (seen by the sensor) to three PWM (R,G,B) signals wich then drive a RGB light strip with a maximum of efficiency.

The trick is to place the Ambilight board in front of your screen and adjust the three potentiometers to make the led strip behave like the picture on the screen. That's all !

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Now, you have a cool little ambilight setup at a very low cost !

Simple Christmas Lights

Christmas approches !! This is the time to begin to think of your christmas decorations !

This circuit is an example to build christmas lights yourself...

This circuit is not very efficient, but simple and fairly reliable (if you use the protection part of the circuit).

The cost is not too high considering that you can easily customize the colors and number of LEDs !
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For this circuit I choose to make my own little PCBs, all by hand (ghetto style !)

Since the circuit is on 230Vac, make sure the isolation between tracks is at least 4-5mm (the best is olso to apply a soldermask, if you can )
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I put the protection/rectifying board in a nice little box.
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As we are dealing with mains voltage, don't forget to put heatshrink tube on EVERY EXPOSED PART !!! It's for your safety !
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There is the result (using Blue, Warm white and amber LEDs)
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You can now Build you own christmas lights (hurry up, santa is close !)

>>>Older posts : Go to page 2<<<

Contact Info


Want more info - go to my "about me" page