rosso@sco.COM (Ross Oliver) (12/09/88)
I have recently been looking at uninterruptable power supplies (UPS) for my microcomputer. It runs UNIX, and is up 24 hours a day. All the UPS's I have seen are of the same basic design: they take 120-volt line current, and transform it down to somewhere around 12 volts to charge batteries. While the power is on, the 120 volts is also fed to your computer. When the power goes out, the UPS cuts over to battery power. The 12 volt battery voltage is boosted back up to 120 volts to be fed into the computer, where it is transformed back down to 5-12 volts to run the computer's electronics. As I understand it, some very complex circuitry is required to convert 12 volts DC to 120 volts AC with a clean enough sine wave for the computer's power supply to function properly. This is one of the reasons that UPS's are so expensive. It seems to me that it would be much easier and more efficient to move the batteries between the computer's power supply and the computer itself. This would eliminate the wasteful transformer and costly translation circuitry. It would also reduce or eliminate the switching time (the time between when utility power is lost and battery power kicks in). Does anyone know of a commercial UPS that works in this way? Has anyone experimented with this possibility? Are there any micros that have this capability built-in? Ross Oliver uunet!sco!rosso
cjl@ecsvax.uncecs.edu (Charles Lord) (12/11/88)
As for computers that do what you suggest off-the-shelf, most laptops work just that way. I used to use an old Datavue 25, non-backlit LCD and all, just because with AC and batt was a "built-in" UPS. Those usually have a 12V to 5V DC/DC conv with a wall xfmr. There is at least one batt based PS for the XT/AT/386 boxes that has an intermediate battery stage. The problem with this type of system is that the computer needs relatively accurate and highly stable supply voltages, and would require regulating pre-battery and post-battery. The typical micro's PS is a switcher that rectifies 120VAC to 120VDC (nominal), then switches at a few kilohertz through xfmrs to the regulated voltages. There is never a 12v +/-3v intermediate stage. What you CAN do is what a friend did years ago with his Apple ][: He wired a bank of 10 each 12V gel-cells (a 120v battery) at that 120VDC stage in the Aztec power supply. Worked like a charm back in the days when UPS meant megabucks. -- * Charles Lord ..!decvax!mcnc!ecsvax!cjl Usenet (old) * * Cary, NC cjl@ecsvax.UUCP Usenet (new) * * #include <std.disclamers> cjl@ecsvax.BITNET Bitnet * * #include <cutsey.quote> cjl@ecsvax.uncecs.edu Internet *
MJB@cup.portal.com (Martin J Brown-Jr) (12/12/88)
I believe that what you have described is not a UPS, but a BPS (Backup Power
Supply). True UPS's always are supplying battery power to the computer and
therefore there is no switching time. There is alot of advertising these days
for UPS's with switching times, these are mutually exclusive.
- MJB -wte@ncrcae.Columbia.NCR.COM (Bill Eason) (12/12/88)
There was a review in December or January's (88/89) Byte magazine about a product called "Boomerang", I believe. It was a small battery and circuit board which are mounted inside the PC between the power supply and the ??? (disk drive?). It has a RAM-resident driver program which detects power loss and stores memory, etc to the hard disk. Upon powerup, a simple command will reload the driver and all that was in memory and put you back right where you were when the power went off. This command can be put in an AUTOEXEC.BAT file so that you always return to where you were the last time you used the PC. They recommend a second piggyback battery for ATs and those with extended memory. Price was 200-300, if I recall. Note that this isn't intended to let you run off of battery power, but it will prevent data loss through accidental (or intentional) power loss. I have no connection to this except as an interested reader. -- Bill Eason (803) 791-6419 ...!ucbvax!sdcsvax!ncr-sd!ncrcae!sauron!wte NCR Corporation ...!rutgers!mcnc!ece-csc!ncrcae!sauron!wte E & M Columbia 3325 Platt Springs Rd. West Columbia, SC 29169
root@conexch.UUCP (Larry Dighera) (12/16/88)
In article <4003@ncrcae.Columbia.NCR.COM> wte@ncrcae.Columbia.NCR.COM (Bill Eason) writes:
=>There was a review in December or January's (88/89) Byte magazine about a
=>product called "Boomerang", I believe. It was a small battery and circuit
=>board which are mounted inside the PC between the power supply and the
=>??? (disk drive?). It has a RAM-resident driver program which detects
=>power loss and stores memory, etc to the hard disk.
Has anyone written UNIX device driver for this product yet?
Larry Dighera
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