Hacked Gadgets Forum

April 6, 2010

PC Fan Failure Alarm

at 6:44 am. Filed under Computer Hacks, DIY Hacks, Electronic Hacks


If you need to monitor a fan on a piece of equipment this PC Fan Failure Alarm from PCB Heaven should fit the bill. The RPM monitor line is used to determine what the RPM of the fan is and if it falls below an adjustable threshold the alarm is tripped. Heat buildup due to a faulty fan can do some serious damage in a short time, this simple circuit could save you some headaches. The schematic is provided here so you can build your own.


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10 Responses to “PC Fan Failure Alarm”

  1. Pouncer Says:

    Could have used this a few month back. Very nice!

  2. Pete Says:


  3. Pouncer Says:

    How is that link relevant?

  4. Pete Says:

    Pouncer: it is relevant because it is describing the EXACT same thing that the original project describes but built in to some mobos. Alternatively you could have read the summary in the link but I can post it here for you.

    During normal operation or in Safe mode, your computer may play “Fur Elise” or “It’s a Small, Small World” seemingly at random. This is an indication sent to the PC speaker from the computer’s BIOS that the CPU fan is failing or has failed, or that the power supply voltages have drifted out of tolerance. This is a design feature of a detection circuit and system BIOSes developed by Award/Unicore from 1997 on.

  5. Alan Parekh Says:

    That is funny, instead of playing a song wouldn’t a computer voice that said fan failure be much better…

    Well I guess maybe the tune is supposed to make you happy so that the failure of your system won’t feel so bad.

  6. Pouncer Says:

    I must have misread it, because all I saw was about the power supply voltages drifting out of tolerance. My mistake.
    That wouldn’t work for my situation since I have a fan on my GPU, and that’s where I would have needed this before.

    I think it should play “Taps” when the failure occurs.

  7. vic Says:

    Pete: err OK but many other things need fans and could benefit from this circuit, and most motherboards have only a few fan connectors, leaving the others directly connected to the power supply.
    Also I didn’t see at what point his circuit plays Für Elise …

  8. Pete Says:


    Well, if you really want to get down to it, yes, the original circuit did not play Fur Elise but, the principal functions are the same. Also, I have never needed to know when a fan was spinning. Me and the electronics the fan is cooling don’t care if the fan is on or off; just that the temperature is in a safe range. You could have a fan whizzing around all day and still be over temp. Laptops for instance, notoriously clog up their air intake ports with dust and the fan is still running but they overheat.

    Having said all that, I was only posting the link because it is a pretty obscure (and interesting) thing that they play classical music. I did not say anything negative about the project in question.

  9. DIY – Detector de RPM de ventoinha de PC Says:

    […] aqueles que gostam de controlar as ventoinhas de um determinado equipamento podem usar este detector de RPM de ventoinha da PCB Heaven. Aquilo que este circuito faz é monitorizar o número de rotações por minuto (RPM) […]

  10. Custom Men of War Game Console - Hacked Gadgets - DIY Tech Blog Says:

    […] probably remember PCB Heaven for the PC Failure Alarm from earlier this year. Giorgos Lazaridis of PCB Heaven has just completed his next project, it is […]

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