Hey guys, as has been mentioned on here a few times before, there are a few of us looking into Stargate DHD's... in my case, to turn the PC on (actually, I know of at least two other people trying to do it)... So far I've looked into logic circuits but someone on OCAU actually mentioned that I should use a PLC or PIC to control it, rather than $400 of relays etc The basic requirements were: - 9 Digit code - 39 Different buttons - 1 Submit/Accept/Send/Confirm Button - Light up of button when pressed Extended Requirements were: - Start disk spin when first button pressed, lock first chevron about 3 seconds afterwards. - Lock chevron 3 seconds after next one is pressed. - Wait 2-3 seconds after Submit button is pressed to engage the gate (and turn on blue LED) Obviously if it fails, I want it to reset the circuit, but that part generally isn't considered hard (just hard power reboot if all else fails)... Now I know where to source th parts for buttons, LEDs etc, but as for PLCs/PICs they're totally out of my league... anyone here either know where I could read up on them, or could tell me enough of what I need to know to get me started?
I would use a picaxe, if you haven't used a pic before, and multiplex the buttons. That way you could convert 39 inputs to 6. If you get a picaxe 18 or 28, they will both have enough inputs, so you can just read the binary data from the 6 pins.
You need 39 buttons, actually 40 buttons total. So, what i would do is wire them up in a 5 by 8 multiplexed array, and connect the 8 columns to something like a 74LS138, and scan through them. So you only need 8 port pins on your microcontroller for the buttons in total, 5 for the 5 rows and 3 for the inputs to the '138.
This is useless it could be bypassed by a screwdriver. So unless you are going to somehow lock your case then there is no reason to bother.
Alright I will be encouraging. Ok if you like Stargate enough then maybe you should go through with this mod. But why do you want to protect your computer with such a system is their someone untrustworthy in your household? I suppose there is a sort of novelty factor in having your computer protected by a code. Although I think this system would get quite annoying every time you want to turn your computer on you have to enter a nine digit code. If I have read the description correctly you will have to wait three seconds in between each digit and another three seconds after the submit button is pressed, thats thirty seconds before your computer will boot. Overall I think it would be better if you left out the extended requirements as it would be annoying having to wait for each chevron to lock and it also looks quite complicated.
you could use several flip flops wired one after the other, with all the set pins attached to the required combination, and all the other buttons attached to the reset pins. personally i would go with the PIC solution tho, but i thought id put in anoher method for you to consider
hi people. You could try and expand on this here: http://jap.hu/electronic/combination_lock.html looks quite hopeful! -Alex
It's more of a question of people not being able to shut the damn thing off at LANs while I'm playing. UPS and the cables are under the desk... but there will always be those that press the button while you're playing... Yeah, Goth actually mentioned that on the OCAU forums a while back, but the PIC has the added coolness factor. @Bigal: ta Explains what I need to know too
Maybe you should get a keylock switch like this http://www.e-switch.com/product.php?series_name=KO in series with your normal push button power switch and have your case in a Stargate theme.
Uh.... Why do you do case mods? Because it's cool, not because it's useful. Besides, you don't have to wait 3 sec between each chevron. The non-earth DHDs let you dial as fast as you want.
I'm sure that there would be an easy way to implement a "skip all this" button. I can't suggest anything that hasn't already been said except for the reminder that you're going to need to implement a "reset" swtich in with the gate-engage button. That way, when you press the big red button in the DHD, it will reset the switches so that the buttons are defaulted to their "ready to be pressed" state. There may be a way to use standard logic circuitry for the not-needed chevrons such that the coding for the microprocessor is simplified. I [Edit]don't[/Edit] recommend the Parallax Stamp. While it's certainly not the most powerful (or cheapest) option out there, the user base is pretty large so getting help or coding examples could be easier.
Do not go for a basic stamp, they cost a fortune, about £40 usually and they need a big circuit board. Go for a picaxe, you program them in simple basic, and they cost about £3.
I think it would be possible to not have to use multiplexed inputs as you could have the nine digits that make up the correct code attached to individual pins and the thirty buttons that aren't in the code connected to the same input. Then program the PIC or picaxe to fail the procedure and loop to the start if the pin that is connected to the 30 fail buttons goes high.
I just went to picaxe's website, and quite frankly, it does look like a better option than a stamp. I keep forgetting that US products have different international availability and cost, as well as vice versa. I should have looked into this more before recommending a stamp. I'm going to learn a bit more about the picaxe and then possibly order a few units to toy with. Unless I get several, the overseas shipping is going to be too cost prohibitive to make the picaxe better than the options more readily available.
Have you tried here: http://www.world-educational-services.com/HomePage.html Good prices on all picaxe stuff and free shipping within the US.
He's not in the US You could use a PICAXE if you want, they're available from Oatley Electronics, amongst other places, or you could just use an ordinary PIC16F628 or PIC16F84.
How is the lock gunna be powered? The PSU outputs shut off when the pc turns off (except the green wire?)
This could be powered from the 5v standby line (purple). The 5 volt line should supply enough current to power the curcuit.
He was responding to me. I recommended a stamp and then he argued that a stmap is too costly and unnecessary for themoocow's needs. Then I agreed with him and rescinded my recommendation after reading a bit about the picaxe. Then I decided I might want to toy with them in the future but overseas shipping is too costly, and 5 mins of googling didn't get me anywhere. SO since I'm in the US, and expressed interest in the picaxe, he provided me with a link to a supplier that ships free to the continental US to avoid me ordering from the direct source and paying an arm and a leg in shipping costs. As for powering the circuit... it may be possible to have a battery source operate the circuit and then engage a standby mode of some kind when the PSU turns on. Think about it. A remote control runs off of two AA size batteries for a pretty long time and my wireless mouse & keyboard run off of batteries for several months at a time.
