Electronics > Projects, Designs, and Technical Stuff

Passive airflow ?

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Jan Audio:
Hi, i am almost going to print my electronic synthesizer casing.
Does it help to add a few holes or a roster to keep the electro cool ?

If i search google for without fan, i only get stuff with fans.
So the air input has to be low, the output high placed, and air input close to the hottest parts.
Does it help without fan ?

Hoe do you keep your electronics cool in a passive way ?

iMo:
What is the power dissipation of your electronics?

Siwastaja:
Note that the passive convection cooling requires a large temperature differential to work. This means, you need to design the electronics to run (including proper lifetime analysis) at higher temperatures than with forced (fan) cooling.

In practice, it's hard to design the heating components to run much below 100 degC with passive cooling, while with fan cooling, it's fairly easy to design them to run at, say, 50 degC (assuming you specify maximum ambient temperature at around 30 degC). This is, of course, assuming that significant cooling efforts are needed at all.

The step #1 is to calculate the actual heating and approximate the cooling through the surface area of your case to see if you need the holes or not. If it runs cool anyway, why bother?

Often testing and measuring is much easier than doing even a crude calculation.

For example, if your components happen to run at, say, 60 degC with closed case, there is no point in adding holes because it runs cool enough anyway, and with such low temperature differential, air wouldn't circulate through the added holes anyway, so they would only bring dust in. But if you measure your components running at 120 degC, nearly destruction, adding a few tactical holes could easily bring it down.

Run the device long enough so that all air inside the case has time to heat up. This may mean hours, or over 10 hours in a large device.

jhpadjustable:
Aren't you concerned about tuning drift due to temperature coefficients?

Siwastaja:

--- Quote from: jhpadjustable on December 26, 2019, 08:20:31 am ---Aren't you concerned about tuning drift due to temperature coefficients?

--- End quote ---

Modern design practice in most electronic circuitry is all about designing stable circuits. Temperature regulation to avoid drifts will likely be more expensive than just designing it to be more stable to begin with.

Of course, in extreme cases, temperature coeffs can't be brought down enough, and more expensive temperature control is needed; typical examples include oven-controlled crystal oscillators or voltage references, but these apply in high-accuracy (often <10ppm) expensive lab instruments.

For an audio synth, frequency stability of a few hundred ppm is definitely good enough even for demanding users, and any crystal oscillator is capable of doing it over the full temperature range.

The question for the OP still stands, what are the losses? I would further say that a synth shouldn't produce very much heat, so if heating is a concern, I'd strongly suggest improving the design to reduce power draw, instead of increasing cooling.

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