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- From: fhl@milton.u.washington.edu (Dean Pentcheff)
- Subject: Battery-powering a PC expansion chassis [SUMMARY]
- Message-ID: <1992Sep12.230409.28337@u.washington.edu>
- Followup-To: sci.comp-aided
- Summary: Yes, it can be done.
- Sender: Dean Pentcheff
- Reply-To: dean2@tbone.biol.scarolina.edu (Dean Pentcheff)
- Organization: Department of Biology, University of South Carolina, Columbia
- Date: Sat, 12 Sep 1992 23:04:09 GMT
- Lines: 175
-
- Some time ago I asked if anyone had suggestions regarding battery
- powering the expansion chassis for a laptop/notebook. We're trying to
- set up a field-portable data acquisition system based on a portable
- PC. It turns out that no one makes laptops with ISA-bus (AT-type)
- slots for an A/D card (with the exception of Toshiba's very
- top-of-the-line models). So... it occurred to me that we might be able
- to use an "expansion chassis" with a generic laptop/notebook, if such
- an expansion chassis could be battery powered.
-
- Ask and ye shall receive. Following is a summary of the replies I
- received, slightly edited for brevity. They are in a format that will
- work with "mail -f", if you want to view individual messages.
-
- Thanks to all who answered!
-
- -Dean
- --
- Dean Pentcheff (Internet: dean2@tbone.biol.scarolina.edu) (803) 777-8998
- Department of Biology, University of South Carolina, Columbia SC 29205
-
- ==========================================================================
-
- From jar@banach.ece.wisc.edu Wed Aug 12 14:03:54 1992
- Date: Wed, 12 Aug 1992 13:02:26 -0500
- From: "James A. Rose" <jar@banach.ece.wisc.edu>
- Subject: Re: Battery powering a PC expansion chassis?
-
- ....
- There are off the shelf "generic" A/D boards which can be driven by the
- serial channel on a PC. They take and send out ASCII sequences to initiate
- sampling and receive data. In some ways, they are a lot like hooking up
- a modem.
-
- How portable (i.e., weight, size, etc.), how long do you have to keep
- running, and how much are you willing to spend? If you don't want to do
- any wiring you could use an UPS (though not as efficient power wise as
- the solution you suggest). There are also IBM PC style power supplies
- with built in batteries and charging circuitry.
-
- The alternative you are suggesting requires some sort of voltage
- regulation and a charging circuit. You could simply use rechargeable
- 'D' type cells which you can buy at your local WalMart. 1.5 volts per
- cell -> at least 12 batteries (to give you 18 volts to be regulated
- down to 12 volts and 5 volts). For longer active time you could use
- a car battery (and add a lot more weight). If you can afford them,
- DC to DC converters are more efficient than regulation (75 to 85 %
- efficient). Also, they can be more stable over wide input voltage
- ranges and do not require as high an input voltage (e.g., +5V in
- gives +12V out). I would be glad to offer further suggestions if you
- have more details.
-
- +------------------------+-------------------------------------------+
- | Jim Rose | Class of '92 |
- | Post Doctorate | Looking for job opportunities in |
- | jar@boole.ece.wisc.edu | Computer Architecture & Engineering. |
- +------------------------+-------------------------------------------+
-
- From rkh@wpi.wpi.edu Wed Aug 12 19:36:41 1992
- From: rkh@wpi.wpi.edu (R Kurt Heinzmann)
- Date: Wed, 12 Aug 1992 19:35:09 -0400
- Subject: Re: Battery powering a PC expansion chassis?
-
- ....
- >2) What sort of batteries might be appropriate for this?
- NiCds or sealed lead acid. I prefer NiCds.
-
- >3) What magical little bits of circuitry would be needed?
- a) Simple, inefficient, cheap way:
- A 6-cell NiCd and a 5V linear regulator plus an 11 or 12-cell NiCd
- plus a 12V linear regulator
-
- b) Simple, efficient, moderate cost ($100 more) way:
- A DC-DC converter that puts out both 5V and 12V plus a battery with
- a voltage in the range required by the converter (probably a 12-cell
- would be best, but you may be able to use a much lower voltage battery).
-
- >4) Is this a totally impractical idea?
- Nope. You should make sure the battery capacity is sufficient to run
- the expansion box longer than the laptop, though. I would buy the DC-DC
- converter, measure the current it draws from a bench supply set at, say,
- 12V or 14.4V while powering the expansion box with the A/D card running,
- and then buy a battery with the appropriate capacity.
-
- Kurt
-
- From tm17@prism.gatech.edu Thu Aug 13 09:46:54 1992
- Date: Thu, 13 Aug 92 09:45:30 -0400
- From: tm17@prism.gatech.edu (MAIER,THOMAS D)
- Subject: Re: Battery powering a PC expansion chassis?
-
- Depending on what the nature of the data is that you want
- to collect (high speed, low speed, what precision, what
- sensors if any) you should consider looking into a battery
- powered data logger. These devices are just a small 8
- bit micro with signal conditioning and A/D with long storage
- memory. Some are handheld and some are benchtop. You
- just start your data acquisition and then when you are done
- you take the box to your computer and upload the data.
-
- Omega sells a couple differant ones.
-
- Omega Technical assistance
- 1-800-872-9436
-
- There are other companies, but I don't have the info right now.
-
- [editorial comment: yes, we're already using one of these. Campbell
- Scientific sells a couple of excellent models. -Dean]
- --
- MAIER,THOMAS D
- Georgia Institute of Technology, Atlanta Georgia, 30332
- uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!tm17
- Internet: tm17@prism.gatech.edu
-
- From lance@helios.ucsc.edu Thu Aug 13 11:48:18 1992
- Date: Thu, 13 Aug 92 08:47:12 PDT
- From: lance@helios.ucsc.edu (Lance Bresee)
- Subject: Re: Battery powering a PC expansion chassis?
-
- yes, I have done this.
- you need data from the manual on the motherboard.
- I would suggest 6 volt lead cells...
- ...why 6 Volt? Because, an XT requires 5 V at 4 amps
- and 12 volt at 1 or 2 amps. The DC-DC converter
- to take the 12 volt battery down to 5 volts must
- run at MUCH higher power than the DC-DC converter
- to take the 6 volt up to 12 Volt.
-
- BUT <-------
- The XT was pretty forgiving of 5 volt level.
- The 12 volts is mostly for drives, and need not
- be as well regualted. So there may be a GOOD case
- for useing 12 volt batteries..with easily available
- photovoltiac charger systems, and regulating down
- to 5 V. Some of the new portables use much less
- power, and if the 5 volt drain is less than 2 amps,
- I would use a 5 volt regulator and a 12 volt battery
- with a pv charger.
- lance
-
- [editorial comment: this pertains to powering a computer motherboard,
- but the general ideas seem applicable. -Dean]
-
- From nagle@netcom.com Fri Aug 14 14:05:08 1992
- Date: Fri, 14 Aug 92 11:02:39 PDT
- From: nagle@netcom.com (John Nagle)
- Subject: Re: Battery powering a PC expansion chassis?
-
- It's easy, but battery life may not be all that great. First,
- try to find cards that only use +5 volts, not +12 and -12, which are
- used mostly for RS-232 signals. If you can find 5v-only cards, you
- only need a 5v supply. Most cards that don't have RS-232 ports don't
- need anything but +5, but this can vary. The manual for the card should
- say how much power it draws at each voltage, so you can tell from there.
-
- A 5v supply can be constructed from any battery bigger than
- 7v or so and a 7805 regulator, which is a 3-pin device (in, out, and
- ground). Radio Shack should have everything you need.
-
- Figuring out where to attach to the expansion chassis is your problem.
- But it shouldn't be all that hard. Find out where the power supply connects
- to the slots, find the +5 and ground leads, get a connector that matches
- the connector on the power supply (any PC repair shop), and hook it up.
- A voltmeter will be helpful.
-
- There are 7812 regulators, for 12V, too. With regulators of this
- type, you lose about 2V in the regulator, so you need at least 14V to get
- 12V after the regulator. Two 9V batteries in series will work fine as
- a source of 18V to be regulated down to 12V. You waste 1/3 of the battery
- life this way, but it's simple.
-
- A more sophisticated solution would be to use a Maxim voltage-conversion
- IC to get 12V from 5V.
-
- John Nagle
-