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Thread: DC-DC Car Power for Mac Mini

  1. #41
    Constant Bitrate
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    the usb button wont work on modern macs, they stopped supporting that awhile ago, with the crt imacs. Anyone here have electronics skillz and is attempting the DIY UPS?

  2. #42
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    You dont actually need the ups. If you use a DC-DC power supply all you really want is something to plug in the usb that makes the computer think it has a UPS connected.

    Then you can make use of the features - consider this:

    You turn the car off and the message of "power off" is sent to the computer. Your machine is still on and powered by the DC-DC converter but will shut down in 10 minutes if the car isnt started and the "power on" message is sent to the computer.

    A simple program could be written to mange this.

    Edit: would also require a small amount of electronics.

  3. #43
    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    Hey mike, I want to buy one of these 19v power supplys from you even without the plugs, do you have any ready to sell? I'm actually looking to power a laptop install that I am about to do, &the 19v along with the 5v for usb sounds ideal.....was you planning on integrating a start up/ shut down curcuit in this power supply or would that be handled seperately?

  4. #44
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    Arrow

    Hi all; great forum..

    so I want to repost some info (from a private forum) about the mac Mini and the power supply, lets start with the fact that I am getting a lot of this info from the horses mouth.. and some of it is just emperical data, I will try and talk to the horse soon enough.

    lets start off with the Apple specs:
    Electrical and environmental requirements
    Meets ENERGY STAR requirements
    Line voltage: 100-240V AC
    Frequency: 50Hz to 60Hz, single phase
    Maximum continuous power: 85W
    Operating temperature: 50 to 95 F (10 to 35 C)
    Storage temperature: -40 to 116 F (-40 to 47 C)
    Relative humidity: 5% to 95% noncondensing
    Maximum altitude: 10,000 feet


    The power supply claims 18.5V @ 4.6A. This give a max power rating of 85W as noted above in the web specs. Now, given there is some margin in this supply, the likely max power you could pull would be somewhere in the 65W to 70W range. This would be from a 1.4GHz mini, with a 1GB power sucking DIMM, optical drive going full power (maybe burning?) and the HDD R/W'ing its brains out, in a hot room so the fan is going full bore, along with full power (up to their fuse break point) being sucked on both USB ports & Firewire port.

    OKay - now that we have that reality in our pocket, lets get on with the business of running this puppy from automotive power.

    One of the first things you will notice is the non-standard power connector - RadioShack and Fry's will not have this in their connector parts inventory. However, if you happen to have one of the newer Apple flat panels, you will notice it uses the same connector on the display's cable octopus - you could always snip this power connector off and repurpose it. Or not. My first order of business was to cut the mini power cord in half (well, maybe 1/3 & 2/3) and attach a set of Anderson PowerPole connectors on both ends. Now I have the ability to move the connector side to other power supplies as I see the need.

    Unfortunately, it got complicated - a key, sort of like the PowerBook power supply key, protects the power to the Mac mini. Without it, the unit will not power on. Here is the breakdown of the connector (as seen from the power supply):

    The connector is symmetric:
    Ground on the outer pins
    Power (18v) on the inner pins
    Middle pin is the signal line

    On my power supply, the signal line is attached to ground through a tiny little 6651? resistor. I have tried this signal resistor as a 6.8k?, a more reasonably available value, and the mini still powers on - so I guess the value need not be exact.

    As I stated above, I chose to wire up the power cable via a set of PowerPole connectors (SinglePole Connector Series): Red/Black on the mini side and Red/Black on the supply side. Easy. I chose to wire up & hide the signal line (6.8k?) in the Mac mini side of the power cable. This avoids the need to run an extra wire/connector from the power supply solely for this power signal key.

    Now for the automotive fun. (horse went to) PowerStream for their DC-DC power converters where I found the ED1010-18. This is an 18v 6.6A (120W advertised) supply that takes in 11 to 16 volts and outputs a clean 18v. The quick specs are: 300mV max ripple/noise, +/-0.5% line regulation, +/-5% load regulation, 88% efficient, 0-40 degree C operating temp. At a cost of only 1/5th that of the mini, this was a bargain! OKay, a tad sarcastic, but I wanted a decent automotive supply for this experiment.

    With the ED1010-18 in hand, a hot soldering iron, and a package of PowerPole connectors, it was time to get to work and put all of this crap together. I started by placing the PowerPole connectors on both ends of the ED1010-18 supply. I had previously added these connectors to the mini power cable, so I was now able to attach the mini to the ED1010-18 supply. To drive the supply from the battery, I built up a Marinco 12VPG cigarette lighter plug with PowerPole connectors. The Marinco part is a high quality plug that locks into place when inserted in the Marinco receptacle (which I have mounted in my truck - replacing the cheesy OEM receptacle).

    I did not add the cigarette lighter plug to the ED1010-18 because:
    1) I wanted to run some tests with the mini running off the 12v battery supply directly, just to see what happens.

    2) If I end up wiring this thing in permanently, it will not go through a lighter plug - it will be hardwired, so the PowerPole connectors are perfect for this eventuality.


    The system:
    Mac mini 1.42GHz, 1GB RAM, 80GB HDD, Superdrive
    Wired Apple Extended Pro keyboard (the older white USB version)
    Wired Apple mouse attached to the keyboard
    Xenarc 700TS 7" VGA display with touch screen USB cable attached to the mini. The display was powered via 120V inverter so was not part of the power draw data.

    Now for the tests: I wanted to know power off current, max current, and max fan RPM. To do this, I ran:
    iTunes playing music from a CD
    iTunes visualizer running in a window
    The HDD attempting to zip an archive of the /Apps & /Lib folders (about 6.5GB)
    (and some other private tool ..that forced the fan on)

    Here is the data: Tests run from both the ED1010-18 power converter as well as from the 12V battery (with engine off)

    12V System -
    Power off/plugged in: 0.018A draw
    3.1A max current draw (with above noted test parameters)


    18V System - 18.2V ED1010-18 Power Converter
    Power off/plugged in: 0.017A (taken from the 18V output side of the supply)
    Unplugged from the mini: 0.088A (taken from the 12V input side of the supply)
    Power off/plugged in: 0.119A (taken from the 12V input side of the supply)
    2.1A max current draw (taken from the 18V output side of the supply)
    3.6A max current draw (2.1A on the 18V side of the supply, not quite 88% efficient based on my gross, non-lab clean, cheap DMM, data gathering).


    There you have it. Hope this is helpful. The most interesting data: 3.1A draw from the 12V supply & mini, and 3.6A draw from the ED1010-18 & mini. Takes 1/2A to run the DC-DC power converter. Well, not quite true since the fan was running faster in the ED1010-18 test so the system was drawing more current.


    you should perhaps note that the fan did not seem to spin as fast/loudly when run from only 12v in extreme usage conditions


    someone making a power supply should be aware of the resistor value and that it can run at a lower voltage, but with possible fan issues..


    btw I would be interested in a beta PS even without the connectors..

  5. #45
    FLAC
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    Sorry for the late response. I've been out of town all week. Hopefully I can answer some of the questions/issues that have been raised.

    turbocad6, we expect to be able to give an eta for production units by the end of this week. And yes, the unit will have a startup/shutdown controller (SSC) like the existing P1280. In fact, most of the features will be identical except that the P1900 secondary output can be either +5V or +12V. The challenge will be connecting the SSC to the mini. We have yet to find the name of the manufacturer of the "ACPI"-like jumper on the mini motherboard (see other posts with pictures).

    vinthewrench, your findings are in line with what we have found (including the sense resistor). However, I would be a bit worried about running the mini on +12V. It's input DC-DC converter was clearly designed to take a higher voltage, and hence less current. You could well be stressing the power components beyond their spec limits (ie capacitor ripple current). This could cause premature failure. Even tho it "works" it is operating outside of its design range. I would recommend caution here....

    Since we cannot find the source of the power connectors used by the mini, our initial recommendation will be similar to your "power pole" connectization. This gives the greatest flexibility for inside the house, and inside the car operation. It does cause a bit of angst when you actually have to cut the power cable, but most of the hard core hobbyists will be willing to do it. The best solution would be a reliable manufacturing source of the original power connector, but so far we have not been able to find the source.

    I'll try to keep you posted on availability later in the week.
    MikeH

  6. #46
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    I guess I don't understand.

    Does the P1900 have a shutdown timer? I looked at the link for the 1280, and I saw that it will shut the box down if the battery voltage drops under 11V. However, what about a hard 30-minute turn-off? Is it possible? (i.e., screw open files, we just want it turn off hard.)

    Chris
    cej102937

  7. #47
    FLAC
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    Chris,

    Does the P1900 have a shutdown timer?
    Yes. The SSC will wait a pre-defined period of time (either 6 seconds or 15 minutes, jumper selectable) before it begins to shut down. After the shutdown sequence has ended, all power is removed from the Mac. However, if you select the "standby" mode (jumper selectable) the P1900 will continue to provide power to the Mac to keep the RAM alive. This is a low-power mode (ie fan off) so that any current draw over about 1 amp will cause the P1900 to fully shut down.

    The Installation Manual for the P1280 describes this is more detail.
    MikeH

  8. #48
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    Wonderful!

    I'll poke around at possible UPS installations, or auxiliary battery installs, but if your power supply has a 15-minute cutoff, I might go that route instead. I think I'm too lazy to put together an Aux battery.

    Christopher Jastram
    http://www.livingresource.net/
    cej102937

  9. #49
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    Talking mac mini pwr connector....

    Hello MikeH and all. I was crusin the web looking for just this exact connector and came across this great site. I've read all pages and then remembered that my buddy is an ADC member (Apple Developer Connection) and has access to information on where to aquire these pieces through Apple. I put in a request to him and hope to hear positive news soon. Will keep everyone posted.


    -Nolan

  10. #50
    FLAC
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    Nolan,
    my buddy is an ADC member (Apple Developer Connection) and has access to information on where to aquire these pieces through Apple
    That would be most helpful! Please let us know what you find.
    MikeH

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