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Improving Heat Dissipation

We’re finding that more of our controllers are now being used in warmer situations, both in hotter countries, and in small enclosures with restricted ventilation. So we thought we’d write this guide on improving heat dissipation.

There are two main ways to get heat away from electronics, conduction and forced air cooling.

First lets look at conduction. The aim is to get the heat from the controller heatsink away into something else as quickly as possible, to do this we need that something else to have the following properties…

  • Have a smooth flat surface with no air gaps [use thermally conductive paste].
  • Be rigid enough not to bend or flex when the controller is mounted to it. Remember that there may be vibration that causes the mounting plate to flex.
  • Have good thermal conductivity – aluminium is 4x better than steel.
  • Be as large as is reasonably practical for your installation. The more mass it has then the larger is the “bucket” to pour excess heat into, the more area it has then the faster that excess heat can disperse.

Heat dissipation by conduction

 

 

 

 

 

 

 

 

 

We recommend mounting the controller vertically if possible, this allows natural air convection to assist with dispersing the heat from the mounting plate.

Now let’s look at forced air cooling. The aim here is to get the excess heat into the air and then away from the controller as fast as possible, to do this we need to pay attention to the following…

  • Fan airflow rate. Although PC cooling fans look superficially similar, there are big differences in the airflow that they can actually shift. Have a search through Farnell or RS to find one with a good CFM rating – around 80 gives good results on our test bench.
  • Mount the fan on spacers so as not to “stall” the airflow.
  • Give the heated air somewhere to go, have vents in the top of the compartment, consider a 2nd fan to drive the heated air out of the compartment.
  • Allow cooler air back in, have vents in the bottom of the compartment.
  • Top tip: power the fan from the controller parking brake socket, then the fan will only come on when the controller is working.

Forced air cooling

We have recently done some tests with the outside of the heat sink spray-painted matt black. This chart shows that the controller ran 5 – 10 degrees cooler than with the bare aluminium finish.

Difference between black and shiny heatsinks

If you still get overheating after that, then it may be time to consider either a bigger controller, or a finned or water cooled heat sink.