Discussion- Multipurpose Onboard Computers: Computer System Units - power - cooling

Note: This thread is a branch from the ongoing "Discussion- Multipurpose Onboard Computers"

CHALLENGES:

• POWER SUPPLIES: 12 Volt supply, with transients, starting etc.
• POWER CONSUMPTION: Computer System Unit: 15 watts or less
• COOLING: 'Cabin' Environment up to 100F, Salt Air
• SHOCK AND VIBRATION: System Board, Power supply, hard drive

IDEAS AND DIRECTIONS:

• System Board: Mini-ITX (7cm x 7cm) 1.2 GHz, 1GB RAM, 12 watts, fanless VIA EN12000EG
• Hard Drive: 1.8" notebook-type drive, 40 to 60 GB, 100G shock rating. Shock mount it.
• Very small 12V switching power supply provides ATX power voltages
• Transient-protected 12 power input, small 12V gelcell backup / protection.
• Mount in sealed, gasketed 'briefcase-like' aluminum box with thermal coupling from heatsink to box. Waterproof seal for cables (How??)

 

I'm not sure if this is what you want these threads to contain, but anyway, here goes:

Just a thought about the waterproofness, but couldn't one have both internal and external (sort of a both-sides connector) installed in the box?

I mean, instead of having a cable run through the casing, one could hardwire the internals to waterproof connectors (not cables) in the casing, and then connect the external cables to these plugs on the outside. Heck, you can even get waterproof headphone sockets like that.

Also, I'm thinking, that one might want to try (real) gold-covered connectors. Not because they look good (which they don't, imo), but because of the corrosion, or lack thereof.

Also, I'm thinking that one might be able to externally shock mount the harddrive. This way you could thermal couple it to the casing in a more efficient way. However, that might be overkill and/or be more trouble than it's worth.

Further, you write that it should be mounted in a "'briefcase-like' box". Personally, I'd choose several boxes over a single one any day. First of all, you'd get more area (relative to volume) per unit. Secondly, a warm harddrive won't heat the cpu. Thirdly, you can do a quick exchange of any of the boxes, without exposing the rest. Fourthly, in a small boat, it might be easier to make room for small boxes in awkward places (or it might not, as it were).

I found some very nice boxes here - although not "briefcase-like":

http://store.qkits.com/category.cfm/ALUMBOX

– still, if your battery pack, power supply and harddisk are external, why would you need to be able to open it easier than four screws?

This site has some nice cases too:

http://www.teko.co.uk/enclosures/enclosures.html

(about a third down the page, they have the extruded gasketed ones).

 

Good ideas!

Good! I grabbed those sites and I'll look in some detail.

-Cables: yes, the sealed connectors would be a nice solution. The right large multipin connector could have power in, display out, and 6 USB's, and audio, and SATA to an external CDROM or HardDisk. There are also big connectors with a mixture of large and small pins, even coax, but they are very expensive. Gold pins definitely.

-HardDrive: a 1.8" 60 GB notebook drive uses only 1 watt, so I think it could air-cool to the inside the box air with no problem. But maybe external. Hmm.

-The enclosure. You're right, no long-term need for an easy-to-open box. But I'd like that for the prototype. The cast-aluminum boxes with gasket would be fine, and inexpensive. The extruded type cases I've seen are not totally sealed.. ??

Thanks for the ideas! If we all keep looking, we'll find answers.

 

Some of the extruded ones on the teko site are rubber gasketed – these are:

http://www.teko.co.uk/enclosures/minitekal.htm

http://www.teko.co.uk/enclosures/tekam.htm

Isn't that 1-watt on average? My 5400rpm 120GB harddrive certainly gets warmer than that when used intensively, playing music, ripping music, watching movies from it etc.

Btw, how about those aluminium sigg lunchboxes (for prototyping – they're relatively cheap)? I don't know if they're thick enough/have enough mass, though.

http://www.mysigg.com/index.asp?PageAction=VIEWCATS&Category=31


Connectors-wise, I really like the circular Hirose-plugs (a pain to solder, though), XLR's (bigger, but sturdier and easier to solder) etc. Both are very nice sturdy connectors which have proven themselves in all sorts of applications.

Hirose also make other types of connectors (firewire, usb etc). Binder USA too, methinks.

I think I'd resist the urge to miniaturise the connectors – everything else miniaturised is great, but not the connectors.
I like "full-size" ones - simply because of the more area and sturdiness you get from that – that is especially important in a system that will get vibration, bumbs and so on (and the reason all professional audio recorders use full size XLR microphone inputs, and the best of them use S/PDIF (coaxial digital) line input/output connectors).

 

Enclosures

DB, OK got those enclosures. Years ago, there was a Heathkit 2 meter Ham radio that everyone called the LunchBox because it was that size and shape and had a handle on the top like kids lunchboxes..

I will pull out the Hard Drive info I collected and post about it. I think the 1 watt is correct for the 1.8 inch miniature notebook drives that run on 5 volts only. What size is the one you mention?

I'll do some more looking at connectors. I'll talk to my Son at nrgsystems.com about what they use on the mountains..

I'll be putting up more information in the different threads here, today (China time, Evening in US, middle of the night in Denmark.

 

Great

The HD I'm talking about is 2.5 inch (it's in a Macbook Pro) – the iPod (the non-nand one) uses a 1.8 inch hd. Even then it still sounds like very little (1 watt, that is).

 

Powering Onboard Computers

This is the solution I'm going to use when it gets here:
http://www.mini-box.com/M3-ATX-DC-DC-ATX-Automotive-Computer-car-PC-Power-Supply

This runs from 6 volts to 24 volts input (keeps running even on cranking battery) , is tiny (plugs right into my Mini-ATX system board, and 90%+ efficient.

Quick specs: Plug-In Smart car PC PSU
- 125 Watts (150watt peak) PSU
- 20pin ATX, 6-24V wide input range
- Programmable timing settings
- Intelligent shutdown controller
- ON/OFF motherboard control
- Survives vehicle engine cranks
- Battery deep discharge prevention
- High efficiency, 125 watts output
- "Anti-Thump" Amplifier remote control
- < 0.5mA standby current
- VIA, P4 and AMD CPU support
- manufactured by mini-box.com

Sounds like a good onboard computer solution. I have an earlier version I'll be running this week and I'll post about it.

 

What in the world is an "- "Anti-Thump" Amplifier remote control"? Some sort of reverse loudness-button? Low frequency cut-off?

Anyway, certainly keep us posted - I think it's great you're giving it a go

Ooh! Just read the link - turns out it supports Intel Core Duo as well!

 

Thump!

These mini-PC power supplies are often used by Car Computer guys, who seem to be required to have at least a 500 watt SubWoofer system hooked up to the computer's audio output. Powering up the PC while the amplifier is on sends a quick transient that sounds like a huge click or thump through the amplifier. This signal mutes the amplifier until the PC is settled.

If some of us use Voice or Sound output onboard, this might even get used...

 

I see - it all makes sense in that context

 

HARDWARE! Not just paper anymore...

YaHoo! I got the prototype off the dock... I have the VIA EN12000EG system board with 1 GB RAM and the PicoPSU-120 12 volt power supply running on 12 volts.

I am temporarily using a older 10GB HardDrive and CDROM drive, and older LCD Display, mouse and keyboard. Couple photos below, showing the bench setup.

I installed a Tiny XP operating system that is running using only 40 MB of RAM! The Windows folder is less than 400MB on hard drive.

Here are some power results. NOTE: This includes the older 3.5" hard drive, which is about 1/2 the total power, I think. I'm getting a 1.8" Notebook drive soon, I hope, as a Chinese friends is searching thru the electronics market here.

Current
(AMPS)-------(Function)------
2.5 Initial boot, hard drive spinup
1.4 Fully booted, idle
1.6 Loading a large application from disk
0.98 Sleep mode: HardDisk off, comes back in 5 seconds if key hit
0.14 System powered off, Power Supply on.

That's 17 watts running, with an old hard drive that gets hotter than the system heatsink! So this is definitely in the area I wanted to get to!

The heatsink is running 38C 100F with no fan in sleep mode. 110F running OziExplorer.

The 12 watts total in sleep mode would be good for sail cruising, where the system will come back alive in 5 seconds.

The MONITOR power is another whole issue. I'll be working that, but a conventional LCD display that runs from 12 volts is 20 to 50 watts, depending on backlighting etc. The one I'm using can be powered off and then comes back in less than the 5 seconds the system takes to come out of sleep, so it would still be 12 watts in the sleep mode.

I'll be testing Hibernate mode, which saves the system, shuts down completely, then reloads to the exact place you left off, applications running, etc.

I'll be testing OziExplorer moving map with simulated GPS and simulated depth soon, to see how it behaves under sleep mode.

Here's the system board, disk drives and battery in background. That little thing with the 2 yellow squares is the complete 12 volt to ATX power supply!



A longer view showing metering and temporary homebrew "control panel"

 

Efficient power saving? Booting VS Hibernation times

I never tried the XP Hibernation thing before.. It saves the complete state of the PC, applications loaded etc.

The system I'm prototyping has timings like these (seconds):

60 cold boot (Not bad for XP!)
60 warm boot
40 Hibernate / shut off (complete power off)
26 Wake up from hibernation with applications (OziExplorer) running, map displayed

15 load FoxFire browser
05 load OziExplorer
03 load new large map in OziExplorer IN OZF3 FORMAT (recommended)

For sail cruising on a very tight power budget, hibernation when not needed and the ability to have a running NAV screen in 26 seconds sounds good. A way to power off the LCD display at the same time would be good too.