Saturday 28 June 2014

Building a Wooden Ghettoblaster: Painting faux rust on the speakers (part 4)

This is the final post on how I built my wooden ghettoblaster.

While my previous my three previous building the front face, the enclosure and wiring it all), this post will describe the final touches I brought to this project: painting faux rust and quieting the fan of the cheap Chinese power supply.

On right you can already see a picture of it completed. It is a bluetooth 2x150W RMS wooden boombox. The sound is really great.

Applying the faux rust paint

Painting faux rust on the speakers
For this to work, you need three colours: black, brown and orange and need to make random patterns. The thicker the painting you have the better effect you will get. Because I had only spray paint cans of these colours, I put a little sawdust in it (I had plenty ;-)

For those wondering the the type of paint brush I used... I used 4 or 5 cotton buds (qtips) taped together (see picture).

You will find below a really good video on YouTube explaining how to do it.

Quieting the power supply

LM35 temperature sensor on the
PSU heatsink
I had a couple of Arduinos Pro Mini 168 lying around and never really used them because they have so little memory. Combined with a LM35 temperature sensor (and some other parts) I built a fan speed controller to adapt the speed of the ventilation to the needs of power supply (the original diagram and source code was found here). 

This means the fan will spin faster only when the inside temperature of the power supply is high making more noise only when really needed (which is usually when you play loud music anyway).

The washer I used to attach the
LM35 to the heatsink of the PSU
The tricky part is to attach the temperature sensor inside the casing of the power supply. To do this I used the rectangular washer of an old VGA connector (picture on the left), then drilled a 2.5mm hole in the heatsink. You need to make sure you leave no metallic shrapnel inside the PSU or you might make a short.

To make the thread I used a tap (see below). I used a 3mm one because it matches the size of typical computer case screws and I have plenty lying around.

Note: to make sure you get a decent temperature reading, it is always better to put thermal paste between the heatsink and sensor.

The LM35 secured on the heatsink (on the right)
The fan speed controller is velcroed on the left

 My wooden ghettoblaster is completed 

Et voilà, my wooden ghettoblaster is completed (at last!)
As a short conclusion, I really enjoyed building this boombox from scrap parts I had laying around but at the end of the day, it took me so much time I would probably not do it again...

Please do not hesitate to post your comments/remarks below.

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