faunt@dustbin.cisco.com (Doug Faunt N6TQS 415-688-8269) (07/10/90)
I would like to be able to run a standard PC/AT clone on 12V, efficiently. Where can I get information on buying or building a reasonably low cost power supply for this? thanx, and 73, doug -- faunt@cisco.com 415-688-8269
dbell@cup.portal.com (David J Bell) (07/13/90)
Doug, you should have very little trouble, as far as I can see... The drive motors operate off 12V (the car is a little hot for that, but it really *shouldn't* be a problem), and the electronics requires both +5 and -5 volts. The plus 5 you can get with one or two regulators; you should probably allow for as much as 5 Amps - maybe run the drives off one LM117 and the mother board off another... The only sticky one is the negative 5V. There are standard circuits in the applications notes for low power inverters. The -5 only needs 100 milliamps or so. I suppose you would also need -12 for RS-232, too; maybe you don't need that in the car? Dave dbell@cup.portal.com
ardai@teda.UUCP (Mike Ardai) (07/17/90)
In article <31677@cup.portal.com> dbell@cup.portal.com (David J Bell) writes: >[...] the electronics requires both +5 and -5 volts. Before going crazy hacking a -5 volt source, make sure that something in the machine really uses it. It was originally used as the substrate bias voltage for the 4116 (16K) DRAMs that were on the original motherboard. The only card that I have seen lately that uses the -5 volt supply is the MicroMint imagewise PC frame grabber. Same with the 12 volt supplies, but they are used for serial ports. I would regulate the 12 volt supply, and as for anything that goes into a car, use a noise filter and big zener clam or crowbar, since you can get some really nasty spike. /mike >Dave dbell@cup.portal.com -- \|/ Michael L. Ardai Teradyne EDA East --- ------------------------------------------------------------------------- /|\ ...!sun!teda!ardai (preferred) or ardai@bu-pub.bu.edu
cb@cci632.UUCP (Just another hired gun (n2hkd)) (07/18/90)
In article <31677@cup.portal.com> dbell@cup.portal.com (David J Bell) writes: >Doug, you should have very little trouble, as far as I can see... > >The drive motors operate off 12V (the car is a little hot for that, but >it really *shouldn't* be a problem), and the electronics requires both >+5 and -5 volts. The plus 5 you can get with one or two regulators; you >should probably allow for as much as 5 Amps - maybe run the drives off >one LM117 and the mother board off another... The only sticky one is >the negative 5V. There are standard circuits in the applications notes >for low power inverters. The -5 only needs 100 milliamps or so. I suppose >you would also need -12 for RS-232, too; maybe you don't need that >in the car? > >Dave dbell@cup.portal.com I wanted to add a few things.... 1) the rs232 drivers can be replaced with MAX232 chips which only require 5 volts (instead of the 1488/1489 combo). 2) Many of the 12" monchrome monitors run off of 12/15 VOlts 3) You should still regulate the drive voltage 12V or you might have soem problems. 4) the -5 at 100 mills can be synthesized using cheap DC to DC converters (off the shelf). 5) I would suggest an auto shut down if the working voltage execedes the IC specs (ie4.75V ) because of data integrety problems. Maybe other than the monitor supply a drop in car to PC power supply could be built using the existing PS casing, Good news for Packet Radio, portable One... . -- email: cb@cci632 or !rochester!kodak!n2hkd!curtis Curtis Braun, N2HKD, Computronics, PO Box 1002 Fairport NY, 14450