powering my B.O.E. from a PC

willthiswork89

i have been looking into adding a RFID security feature in my PC for a few reasons, it will sell quicker and i have sisters and a girlfriend who decide that my computer can be shutoff when they feel like it regardless of what i have left up running including school work and my BS2 Projects. Now the homework i can spare but i just cant have it for the BS2 haha! i that thinking about implementing my B.O.E or my Homework board(probably my homeworkboard) into my PC with an rfid reader and a relay or some sort of switch to disable the power button and restart button from being pushed when its armed.

The Problem:

I Figured ide make it easy for those not wanting to hear the story and make this little skip-section, seeing that if i sell this PC i do not wish for them to have a problem with dead batteries and i wanted to know if its possible to run off the PC power supply. I have come to a major problem being i dont want to fry the microcontroller and that when the pc shuts off so does the juice to the supply. How can i hookup to the power Supply But run off the battery when needed also?

allanlane5

It would probably be easier (and safer) to build a ply-wood box to put around your PC, to keep little fingers from pressing the power button. You could set it up so you put the keyboard in there too.

Tricky Nekro

This circuit you seak for can be very simple or very complicated depending on the control you want to have over the A.T.X. (I think thats the acronyms for PCs' power supply)... Ok, now look...
You can built a PWM based on 555 and enable it by stamp... But stamp must also check the outputs of the ATX so forget it........ You will probably destroy your PC...
The only thing you can do is to replace the power botton with a relay (I don't know for other motherboards but mine's just a push botton connected to it) For best results you must have a battery pack that recharges through the PC supply... Or else you can use a wallpack for powering up the stamp... And the PC power supply needs·to filter, stabilized by a diode bridge(some time it may switches, I don't know that just heared it somewhere) and regulated... Think you can make it... It's ok but you better change chassis...

And one more thing... the power of the computer isn't turned down by software???????

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Mike Green

You can buy a simple lock switch that's SPST (single pole, single throw) momentary contact. In other words, it has two terminals and they're connected together momentarily when you turn the switch. The switch has a spring so it goes the other way (to its open position) when you release it. You disconnect the reset switch and connect it to one lock switch. You disconnect the power switch and connect it to the other lock switch. This assumes that there's a power button on the front that actually switches a logic level (rather than the AC supply). Now only the person with the keys can either reset the PC or turn it on. You turn it off by using shutdown. If the original power on switch is not a momentary contact one, but has to remain closed to keep the PC on, you can get a similar non-momentary contact lock switch. Some lock switches require you to leave the key in the lock in the on position, some don't and allow you to remove it in either position. You'll have to drill holes in the PC to mount the lock switches and you need to make sure there's nothing in the way since the switches are fairly bulky.

If the PC has a power switch on the back that actually disconnects the power from the power supply (usually it's a red or black rocker switch that's built-in to the power cable connector assembly or is next to it), you may not be able to easily replace this. Best is to make a cover that's screwed on, usually out of a piece of plastic, that prevents busy fingers from flipping the switch easily. You have to be very careful how you fasten the cover so that the screws don't contact any wires or connectors inside the case. Sometimes there are existing screw holes that you can use by substituting a longer screw (again being careful about how far into the case the screws project).

Post Edited (Mike Green) : 8/13/2006 5:12:28 PM GMT

Franklin

I think you are throwing too much technology at a simple problem. Just relocate the power switch Iif this is an atx power supply) to another location, say the back of the computer. Other alternatives are to lock your room and get a new girlfriend that respects your things.

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- Stephen

sailman58

The gals are going to complain no matter what you do, so take the easy way out and put the computer in a locked room.

willthiswork89

but why take the easy way out! haha i suppose it could be run by a 9 volt i could build a compartment for it. i have a wireless mouse and keyboard and i thought about taking the power wire to the receiver into a relay, disabling the mouse from use but since ive been trying to sell the tower i thought well hmm i bet i could disable the buttons from being pushed in turning the pc off, and when its off if armed have it not be able to turn on but i never though about the these buttons work, i was thinking that the buttons worked by sending a pulse to the mother board and that reacts, not a push button. Thanks for the info ill tinker with it when i get my receiver and see what i can do!

Beau Schwabe

willthiswork89,

I've never bought a used PC, I've always lobotomized and upgraded what I have or bought something brand new. I'm just curious if ( In today’s "disposable" society ) the amount of energy
and effort you are putting into your "tower" is worth the re-sale value. What I'm trying to say is that you might be better off trying to upgrade what you already have and learn something along
the way or save up for something new in the future. (<-- Suppose the same analogy could be applied to the girlfriend)




As far as keeping this "ON-topic", the RFID reader idea is ok, but again... I'm not sure this will impact your resale value to energy/effort ratio the way you expect it is going to.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 8/13/2006 8:01:36 PM GMT

willthiswork89

Beau my computer was built by yours truely, i did learn alot along the way, regardless even if it doesnt sell i though it would be a cool addition to the PC on my own behalf.

Chris Savage

On an ATX System what is to stop them from selecting Start, Turn Off Computer...?

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Chris Savage
Parallax Tech Support
csavage@parallax.com

sailman58

Chris, I suspect that that call could be intercepted and redirected, but that would be Windows system programming and way off topic! Physical security is the only answer, because that is the only way to prevent unplugging the machine and rebooting that way. That, by the way is what we have to do at work when XP locks up. I guess the rocker switch is too expensive, so none of our PCs have tham.

Ron

willthiswork89

My power supply has a rocker on it, nothing prevents this but were talking about a 9 year old lol, they dont know about rockers and stuff, theres a button on the front that they know will make me mad. my girlfriend just gets on the pc and messes on it so i can disable the mouse... being a PC programmer with WINDOWS c++ knowledge i can easily bypass the ability to turn the PC off that way, i just have been trying to think of some cool things to do with the RFID including putting it in my car to disable the starter which would be awesome but i dont know.

Franklin

Now that would be a much better use of RFID. (the car thing)

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- Stephen