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#16
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Turn on computer using power strip
In message , Paul
writes: J. P. Gilliver (John) wrote: In message , Paul writes: [] the schematic. There's a 4.7K resistor to +5VSB and there would be 1 milliamp sunk to ground on the motherboard end of PS_ON# pin 14. [] Or slightly over 1 mA, of course. Isn't it funny that resistors (and capacitors, and many inductors) are still made to the E12 series, which dates from when they were sorted into bins as they came out of the machine that made them, whereas they're usually precision-made to 2% or even 1% these days! It's a pullup resistor. Just an order of magnitude of current flow is required in a discussion of such. You could use a 4.7K 5% or a 5.1K 5% and nobody would know the difference. Oh, I knew that. I was just meaning that it amuses me that resistor manufacturers still make (and therefore people specify) resistors in a range of arcane values, the reason for which disappeared decades ago - but they still do, and _don't_ make rounder values, except at higher cost. In this example, you'll have to look a _little_ harder to find, say, a 5k one than a 4k7. I'm feeling nostalgic now, for my TI Bible... It probably had the equations spelled out for working out what pullup to use :-) [It would involve a discussion about wired-OR logic using open collector drive, N outputs wired to M inputs, and what pullup resistor is required.] In this case N=1 and M = approximately 1. Yep, I remember those - all the TTL series and fanouts between them (I think they could always drive at least 1 whatever mix), LS, L (remember L?), S, AS, F, ALS, C, 11000, ... at one time I used to know many of the numbers by heart too, and still can quite a lot of them. https://cdn.eeweb.com/articles/artic...web-dsl-01.jpg And switching a 1mA current flow with a relay, may not provide enough current to keep the relay contacts clean. Relays have a maximum current, but they also have a [] (I started out in a switchgear company, where their smallest unit - something like LMS10, or TJM10 - had a normal carrying current of 2kA, and a breaking capacity of 10kA. That was down at 11 kV and distribution; the ones for grid were somewhat bigger. Ah, happy days ..) -- J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf Never be led astray onto the path of virtue. |
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#17
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Turn on computer using power strip
In message , Ant
writes: Someone told me it was a bad idea to everything on from a power strip. Is this true? [] Like all such advice, it's an oversimplification. Paul and Rudy have given reasons why - and how! Basically, turning everything _on_ at once - which is maybe what you mean - can mean quite a large inrush current, especially if several of the items predate regulations limiting inrush currents (or ignore them, especially if made in certain countries). And the switch in the power strip may not be rated for that size current at once. Turning _off_ all at once - provided you've shut your computer down properly of course; shutting it down just by turning it off is not a good idea, but that's true regardless of whether it's via a power strip or not! - shouldn't be harmful; if the equipment is all running normally, then the total current it's drawing - assuming you're not overloading your power strip! - shouldn't exceed the breaking capacity of the strip's switch, assuming again it's made properly. There might conceivably be things that should be turned _off_ in a certain sequence, but for the average home computer setup, I can't think that is common, as long as you've shut down tidily anything that needs a tidy shutdown. (And if I add much more, my answer'll get like a Paul one!) -- J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf Why doesn't DOS ever say "EXCELLENT command or filename!" |
#18
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Turn on computer using power strip
On Sun, 22 Jul 2018 01:23:18 -0400, Paul
wrote: J. P. Gilliver (John) wrote: In message , Paul writes: [] The front button does not have "direct effect". It's a [partially] software mediated button. The switch on the back of the PSU, is a direct effect switch that cuts the mains. If it's there; not all power supplies _have_ the back panel rocker switch. (Or have regulations changed and they have to nowadays?) [] the schematic. There's a 4.7K resistor to +5VSB and there would be 1 milliamp sunk to ground on the motherboard end of PS_ON# pin 14. [] Or slightly over 1 mA, of course. Isn't it funny that resistors (and capacitors, and many inductors) are still made to the E12 series, which dates from when they were sorted into bins as they came out of the machine that made them, whereas they're usually precision-made to 2% or even 1% these days! It's a pullup resistor. Just an order of magnitude of current flow is required in a discussion of such. You could use a 4.7K 5% or a 5.1K 5% and nobody would know the difference. I'm feeling nostalgic now, for my TI Bible... It probably had the equations spelled out for working out what pullup to use :-) [It would involve a discussion about wired-OR logic using open collector drive, N outputs wired to M inputs, and what pullup resistor is required.] In this case N=1 and M = approximately 1. https://cdn.eeweb.com/articles/artic...web-dsl-01.jpg And switching a 1mA current flow with a relay, may not provide enough current to keep the relay contacts clean. Relays have a maximum current, but they also have a minimum current flow they can handle if you expect the contacts to remain clean and trouble-free. Even with a precious metal coating there will still be a minimum current flow spec. I might go looking for a reed relay to do it perhaps. Rather than the contactor off an air conditioner. Contact bounce ? Not a problem driving the front panel Power button. Might need to think about the consequences of driving pin 14 with such. This is why semiconductor drive is "nicer". And in this case, you could use an optoisolator to close the contacts if you wanted. Paul When you are just jumping the power on switch, just about anything will do. They use the cheapest switch they can find and they must have a lot of debounce capability. I was using a small DIP relay and never had a problem. This was in my car, starting up under some of the worst conditions you can imagine. (Heat, humidity, dirty power from a cheap inverter along with the kinetic problems of bouncing around in the back of a car). The best machine for this seemed to be a 133-166 mz socket 7 machine running DOS 6.3 |
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