Re: [linux-audio-dev] OT: Electronic advice for PC.

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Subject: Re: [linux-audio-dev] OT: Electronic advice for PC.
From: Patrick Shirkey (kotau_AT_firstlinux.net)
Date: Tue Apr 30 2002 - 20:49:01 EEST


--- Lamar Owen <lamar.owen_AT_wgcr.org> wrote:
>
>Is this a typical motherboard (ATX) or is this something oddball? My notebook
>requires 19.5V at the DC input -- but there are inside-the-case DC-DC
>inverters that transform to the required internal voltages.
>
>A standard MB takes +12V, -12V, 5V, and 3.3V, plus a signal back to the power
>supply called 'power good' (and then there's the turn-on lead). Standard
>desktop-style hard drives, floppies, and CD's take 12V and 5V. Notebook HD's
>take 5V only. Newer AGP stuff takes 1.5V.
>

It is supposed to be a typical ASUS mobo but its dimensions are 100x150mm so it is smaller than any other standard mobo that I could find here. I had to buy the whole computer to get it as there is only one company that is legally allowed to sell it in Korea and they only sell it as a complete unit (minus cpu).

Incidentally this is intended as a prototype which I can use to get more funding for the concept. A portable, Linux run, professional digital recording device. The target audience is film, television, and radio sound engineers. People who need better quality than a minidisc but don't want to spend excessive amounts on a notebook+usbcard+portable power supply but already have a pci soundcard that they could use to get the quality they need.

>Do you have an existing AC power supply? If so, you need to actually measure
>the current consumed (and the voltage at which that current draw occurs)
>before you can size a battery.
>

Yes and that is also custom made for the board. I don't have it in front of me at the moment but I can remember that it is a 125 watt AC. It is slightly larger than a notebook adapter and is switchable 110/220 volts. Basically it is just a standard power supply just very small. It is also only available with this computer.

> How do you plan to charge the battery?

That is really dependant on what type of batteries I use but ideally I would like to be able to plug into the wall and the batteries are charged without having to take them out of the case. The same way as a notebook battery is charged. I can work around this if it adds too much weight to the case by providing a seperate charger but that means more accesories to lug around on the road which is a negative selling point.

>
>> >2.) Required current. At the required voltage, how much current does the
>> > PC draw? This is necessary for the next criterion:
>
>> Does anyone know what this would be based on the above hardware?
>
>You have to measure this with a multimeter. In case you have never done
>current measurements before, the basic concept is to place the ammeter in
>series with the power supply. This can be difficult, depending upon the
>supply. But, if you can get to one leg of the supply by itself, clamp-on DC
>ammeters are available that will allow you to get an accurate reading without
>messing with the wiring.
>

> As another aside, I carry such an outfit with me all the time
>-- two Power Wheels 7AH 12V batteries plus a 120W inverter, all in a military
>surplus ammo case (7.62mm NATO, the small case). I'm an amateur radio
>operator (KF4MYT), and often need to run my Yaesu FT90 mobile radio outside
>the car. The ammo-pack power-pack does the trick without the inverter. It
>can also run my notebook with the inverter.
>

That's similar to how I want to package it only in plastic for weight saving.

>You may find that the current draw of a typical desktop MB is very high.
>

What is considered high when batteries are involved?

--
Patrick Shirkey - Boost Hardware Ltd
For the discerning hardware connoisseur
http://www.boosthardware.com
http://www.boosthardware.com/LAU/guide/

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