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I am working on a system similar to a 3D printer, which works with stepper motors, heated bed and an hot air fan. This system will work inside a chamber, with a temperature around 4 degrees and around 50% of relative humidity - These variables are concerning to me. I am wondering what measures should I take to avoid the condensation of droplets and effects related to ESD due to the humidity of the environment, which affects to the PCB integrity and can cause short-circuits.

Thank you very much for your answers, Antonio.

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    \$\begingroup\$ How will you maintain 4°C in a chamber with a hot bed and a hot air fan? \$\endgroup\$
    – Transistor
    Jun 7, 2016 at 12:33
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    \$\begingroup\$ 4 C or 4 F? You need to be careful with units. \$\endgroup\$ Jun 7, 2016 at 12:34

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A psychrometric chart will give you several useful figures for your calculations. (This answer assumes that you are working in Celsius / centigrade as any civilised engineer would!)

enter image description here

Figure 1. Extract from Psychrometric chart with operating conditions marked on it.

  • Find the 50% RH curve (circled top right).
  • Mark a point on it above 4°C. This is your operating point.
  • The upper red line is the "dew point". When you reach that condensation will appear.

I have marked up in red two possible ways of getting condensation on your part.

  1. Increase the relative humidity (vertical arrow). Obviously at 100% RH the air is saturated and water will start to fall out of it.
  2. Decrease the temperature (horizontal arrow). You will reach 100% RH at about -6°C.

In short, you have a good safety margin at your operating conditions.

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What you describe doesn't sound like much of a problem. Even if you mean 4 °C, there is very little moisture in the air, especially at 50% RH. Any electronics will dissipate some heat, so the board should be slightly warmer than the air. Even if it were the same temperature, I don't see why you expect condensation.

Basically 4 °C and 50% RH shouldn't be a problem.

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