An experience with passive/fan-less cooling

Passive or fanless cooling is a popular way of reducing size, noise and power consumption in consumer electronics. Instead of relying on forcing cooling air through the machine (via a small fan) you instead rely on convection, heat sinks and suitable ventilation holes in the case of the machine.

Removing the power supply from the inside of the machine reduces the heat generated internally and lower airflow reduces dust build up. However careful consideration is required in terms of layout and airflow routing as well as safety measures. Picture the scene, Leicester city in the Champions league quarter final, an on demand TV box (I will not name the brand) displaying the action and then.. blank screen. Cue cursing and frantic jiggling of cables followed by a power cycle and return of picture (missing a goal however).

So what happened? placing a hand on the box revealed it to be extremely warm, much hotter than I would have considered acceptable. A quick check of the internet revealed that the box is of a fanless design, with a safety over temperature cut out that effectively puts the machine into standby if it becomes too hot. Also the box only sits a few milimeters off the bench and there are no ventilation holes in the top of the box, only the sides and bottom which doesnt look condusive to a healthy flow of air. I must note that the box was sitting on a wooden table not on carpet. Standing the box on its side to achieve a clear vertical airflow route got it through to the end of the match and kept it relatively cooler but moving forward how could the situation be improved.

Not wishing to cut holes in the top of the box the option of blowing air into the bottom of the box was chosen. The presence of a usb port on the rear of the box steered me towards a cheap (£5) usb powered tablet cooler, raised up on a temporary platform of Lego, end result is a cool box and no more drop outs. The platform added about 2 inches clearance between the bottom of the fan and the bench and dramatically increased the air flowrate.

So I have a working solution but should I have had to do this? The detrimental effect of elevated temperature on the life of electronic components is widely documented, however this is probably less important to the designers of the machine in todays society when consumer electronics parts are effectively considered as throw away items. But that's a different story......