Simple Fan Controller Helps Apple II To Beat The Heat

Apple II computer on a workbench

In its day, the Apple II computer didn’t typically require active cooling. However, the increasing scarcity of replacement hardware convinced [Joshua Coleman] to come up with a more robust active cooling solution for his Apple II+, increasing the likelihood that it will keep on crunching numbers for decades to come.

Joshua mentions that he recorded temperatures inside his Apple II+ peaking at 110 Fahrenheit (over 43 Celsius). This isn’t totally unexpected for a fully-loaded Apple II system, and components were built to handle this – the original datasheet for the 6500 microprocessor family reveals that the CPU can handle temperatures as high as 158 Fahrenheit (70 Celsius). Unfortunately, we’re not dealing with brand new components anymore. Decades-old microprocessors don’t necessarily have the same thermal tolerance as they once did. All components will eventually wear out, and heat can certainly accelerate the aging process.

In the interests of maintaining his system, Joshua cobbled together an Arduino-based cooling system for his Apple II+. A temperature/humidity sensor continuously monitors the heat situation inside the case – when things get too toasty, a 12V fan powers up to draw fresh air over the logic board and expansion cards. A simple cooling curve reduces wear on the fan motor and relay.

This is hardly the first active cooling system for the Apple II line – in the 1980s, Kensington produced a popular (if not stupendously ugly) ‘System Saver’ accessory, an external bolt-on fan that kept things running cool. These were often deployed in schools and by power users looking for added reliability when maxing out the Apple II expansion slots, a configuration that could increase temperatures due to the extra power requirements and reduced airflow.

There’s a lot of room to expand on this project. Anyone looking to take this even further can find the project details and Arduino code on Joshua’s blog.

This isn’t the first time that Joshua’s Apple II hacks have appeared on this site. We recently covered his project to print breaking news on a dot matrix printer. Video of that hack is below.


11 thoughts on “Simple Fan Controller Helps Apple II To Beat The Heat

    1. When I built my first A][ clone we wanted to attach XT keyboards, so one of the collegues created a Z80 mini computer running at around 2MHz clock. Its sole purpose was to translate from XT to the parallel Apple interface.

      Those were the days of 74LS, EPROMs and floppy disks.
      …like tears in rain…

  1. The Arduino has more processing power than the Apple does. I can emulate several apple IIs on even my first generation Raspberry Pi.

    The Pi takes up far less space, doesn’t require a power hungry CRT, takes far less power, and can be accessed remotely. There is very little reason to keep this e-waste.

    1. It doesn’t matter if there’s a “reason”. This “e-waste” is the reason why we have come so far.
      For me and many other poeple, that is more than enough to keep these amazing computers from a long gone era alive.

  2. Honestly, fans are relatively cheap to replace, I think I’d maybe just have it running continuously when the computer is on, and rig the microcontroller to notify on failure (perhaps by monitoring the fan’s voltage drop). Trying to cool only when needed seems like it doesn’t add a ton.

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