PowerMac switched power outlet?

Discussion in 'Macintosh Computers' started by DavidCar, Jun 21, 2005.

  1. DavidCar macrumors 6502a

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    Jan 19, 2004
    #1
    Does anyone know of a way I could create a switched power outlet for a PowerMac. I don't have one yet, I'm still thinking about it, but I'm considering a kind of "living room Mac" in an enclosure which would need an external fan that would be sure to be on whenever the Mac was on.
     
  2. 7on macrumors 601

    7on

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  3. DavidCar thread starter macrumors 6502a

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    #3
    In the installation I am considering, someone would be able to turn on the computer from the HD Cinema display without ever seeing the computer, or other things like power strips. In that situation, I need to be sure the cabinet fan also comes on, which won't be noticible from the place where the display is located.
     
  4. stevep macrumors 6502a

    stevep

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    #4
    Not sure if the power supply in a PM is the same as in a non-Apple machine, but I guess there is a spare power supply cable for a hard drive - if so you could use this to drive a low-voltage cooling fan (12 volts). Or if you know what you're doing, use it to power a relay that switches on a mains powered cooling fan - you'd have to make up your own relay with diode protection. Or have you thought about a usb-powered fan?
    7on's suggestion is the simplest. Or you could just switch on the monitor, and then walk over to the 'cabinet' thing you talk about and switch the fan on......how far is it exactly??
     
  5. DavidCar thread starter macrumors 6502a

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    #5
    The general idea is to have a Cinema display hidden behind a picture on a wall with the computer on the other side of the wall. An EyeTV 500 would be accessible from a TV Guest account, so I couldn't count on someone always remembering to turn on the fan. It defeats the elegance of the concept. I also wouldn't want to do anything to void the warranty. USB Power sounds interesting. I'd be reluctant to home brew a USB powered relay, but it is an interesting thought, but I might compare the airflow generated by a USB fan with that required by a PowerMac to see if that sounds reasonable.
     
  6. reh macrumors 6502a

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    #6
    First thing I'd do is use temperature monitoring software to see what kind of temps the PowerMac runs at while in an open environment. This will be your "benchmark" for when you have it in your enclosure to be sure your cooling solution is working adequatly.

    I like the USB power fan idea but you could also use regular case fans. They come in an assortment of sizes (like 50mm up to 120mm) and would be powered by one of your standard power connectors inside the Mac. Couple these fans with some ducting and I think you'd have a pretty spiffy setup.
     
  7. DavidCar thread starter macrumors 6502a

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    #7
    I just got a reply email from the developers of the Systat dashboard widget that they plan to put a temperature monitor in a future version. I know this info is available somewhere else, but I forget where. I don't have a PowerMac yet to work with.

    I have not checked into what "standard power connectors" inside the Mac are available, but I found I've already got an old 5 volt relay I could work with which would match the power available on a USB Port. Otherwise I would have to bring power from the internal connector to the outside of the computer. This may be easier than I expect, easier than the relay.

    The fan would need to fit behind a 4" x 10" grate at the top/front of the cabinet in a way that air would be forced from there through a similar grate behind the power mac with 2" clearance, then beneath the cabinet to a grate at the bottom/front of the cabinet. That would allow room for two 120mm fans. I understand a dual power mac has to work hard (and presumably hot) to decode full size HDTV.

    I'd have to double check all the details, but either with internal standard power, or a USB relay, it appears I could make it work.

    Anyone know where I can find documentation on internal standard power connectors?
     
  8. reh macrumors 6502a

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    #8
    I believe it's called a molex connector, but I'm not sure. It's the same thing that hard drives and cd drives use for power.
     
  9. stevep macrumors 6502a

    stevep

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    #9
    You don't need a relay if you're going to use a standard usb cooling fan (such as this one http://www.directusbstore.co.uk/cnb...catalogue-product_info-null&prodCategoryID=28)

    Neither do you need a relay if you're connecting a standard pc-type cooling fan to one of the power connectors in the mac - hundreds available eg http://overclockers.co.uk/.

    You only need to make up a relay circuit if you want to use one of the internal power connectors to power a mains-voltage fan - the 12v (or even 5v) supply would switch the relay, thus switching the mains supply on. But you have to be careful to protect the power supply from the Mac from the back-emf generated by the relay, hence the diode protection.
     
  10. DavidCar thread starter macrumors 6502a

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    #10
    I hadn't thought about the reason for diode protection. Do I need to put the diode in series or parallel with the relay coil?

    The coil resistance is 50 ohms, so with 5 volts from USB power, that would be .1 amps and .5 watts, which would be within the USB specs, as far as I can tell.

    It would be better if I could find some solution where the USB would power an LED, and the LED would trigger some commercial (not home brew) 120 VAC switch to the fan. I would want to match the airflow of the 9 powermac fans, so that rules out a USB fan.
     
  11. stevep macrumors 6502a

    stevep

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    #11
    This is what I had in mind. The 9v supply should actually read 5v and you may need to lower the value of the 330 ohm resistor to around 180 ohm (I forgot to amend these on the original, sorry). The protective diode is wired in parallel to the input side of the relay, the idea being that any back emf generated when it switches on and off will be dissipated through the relay coil and not through the usb supply. The red led is just an indicator, and you may want to omit it, change it to green or whatever.
    The usual disclaimers apply of course - I haven't tested it and I have no idea if you're comfortable working with mains voltages, but common sense is available to us all for free, we only have to use it! Good luck - maybe you'll let us know how you get on??
    stevep
     
  12. DavidCar thread starter macrumors 6502a

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    Jan 19, 2004
    #12
    Thanks for the diode information. It would be good if I could find a 12v fan or fans and a 12v power supply so I would not be working with 125v. I could probably just solder the relay into the 12v power cord with the diode and a cut USB cable, then wrap it all up with black tape.

    This won't be happening right away, but it would be good if I made a decision before the EyeTV 500 rebate ends next week. I need to think through and then triple check the details before I start ripping my wall apart. But if it all comes together I'll post a note in this thread.
     
  13. ReanimationLP macrumors 68030

    ReanimationLP

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    #13
    I thought the Cinema displays DID turn on the Mac? :confused:
     
  14. punkbass25 macrumors member

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    May 16, 2005
    #14
    i've seen power strips that have a main plug, and then 5 aux plugs, the strip always powers the main plug, and then when you turn on whatever that is (tv, computer, stereo...etc.) it detects the power draw and turns on the other 5 outlets as well

    i saw it in some article about lowering energy cost for your home.
     
  15. punkbass25 macrumors member

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    #15
  16. DavidCar thread starter macrumors 6502a

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    #16
    Thanks for the link. I did a search after I was notified of your first posting, but couldn't find anything.

    Yes, that would be a good solution, and I could even use a 125v fan. I like that because it is simple and gives me several options.

    thanks,
    DC
     
  17. punkbass25 macrumors member

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    #17
    no problem hope this project works out for you!
     
  18. DavidCar thread starter macrumors 6502a

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    Jan 19, 2004
    #18
    If anyone else is following this subject, I checked to see what other pages were linking to the above link, and found the following link, which is to a power outlet switched by a USB connection. Not as much surge protection though.

    http://www.thinkgeek.com/gadgets/electronic/6ee4/
     

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