heh. So, I'm not to the Arduino and hardware stuff in general, so be gentle. I bruise easily. My first project, I'm thinking something pretty simple. I have a beefy server in my apartment that I use for my software projects (that, I'm pretty decent at, just not hardware). I don't leave it on all the time due to electricity costs and simply not needing it on all the time right now. So to learn Arduino and do something useful, I was thinking having an Arduino project that turns my server on for me remotely.
I was thinking of grabbing the latest Arduino Uno R3 (that's the most recent Arduino, yes? So many boards, not sure what's what), a servo to actuate the power button, and some sort of pressure sensor so that just in case, the servo doesn't press the power button too hard. Plus it'd be fun to work with a sensor. Also, I'd need a Wifi module of some sort. For this particular project, I'm not looking to spend too much money in case I break something and don't need too much data to be transferred, but would like to have a very simple web server so I can go to a small webpage on the device, hit an HTML button that says "Power on" and actuate the servo to push the power button. The Wifi module needs to support WPA2 Personal, and at least "G" though "N" would be nice. I don't need DHCP, and actually don't want it, because I need a static IP so I can point my web browser at the device as the DNS and all is sitting on this server in various virtual machines that create my network.
I think that about covers it. Please let me know if you think I need anything. Oh yes, I'd like to have a battery pack so I can just do double A's or something. I don't think the device would need too much power. Then again, that's why I'm asking you people.
If you really want to use a servo, i guess you could. However, it probably would be a lot easier to use a relay or opto-coupler circuit to temporarily close the power button circuit -- tap into the leads where they are soldered to the power button, or use a "line hi-jack" device. You can test that this will work by simply shorting the power button connection using a paper clip when your computer is off -- it should turn on.
An Arduino can run a very simple web server if you add the Ethernet shield. The sample for that shield can likely be changed to toggle the pin for the power-on on for a little bit (500 ms?) and then off again, to simulate the button press.
Yeah, I realize it isn't an elegant solution using a servo, but I'm not really looking for elegance, I just want to learn Arduino so that when I go to some of my more complex projects, I will hopefully have had experience with more shields and sensors.
As for easier, I don't think it would be in this case. Because then I'd have to open my case, cut the lines, solder, and that's just no fun. I have done a case mod before, installing one of these: http://www.directron.com/ec399.html?gsear=1 and it was a royal pain stripping the wires and resoldering them. They aren't actually the solid wire, but the made-of-many-tiny-wires kind of wire. Really annoying. So in the interest of my sanity, pure laziness, and wanting to know how to interact with servos and stuff, I'm wanting to go this route.
Any suggestions on the pressure sensor thingy? Is it necessary for this type of application? Is my reasoning semi-sound in wanting to make sure there's something to stop it from pressing too hard? Another reason is that say it gets bumped or something and it tries to press down on solid case, I don't want the servo burning out because it can't actually press down. Not that I expect there to be much counter-weight preventing it from moving, but just trying to get a feel for things. Like I said, I'm a newbie. Thanks!
To switch on a pc the the motherboard needs 2 pins shorting together for a split second. To switch it off, it's needs shorting for 5 seconds or so. You could bypass the pc switch with a relay controlled by the wifi enabled arduino. The existing pcs switch could also be connected so that you can switch it on locally.
Texy
Micheal:
So in the interest of my sanity, pure laziness, and wanting to know how to interact with servos and stuff, I'm wanting to go this route.
Any suggestions on the pressure sensor thingy?
If your servo is weak enough, you don't need a pressure sensor. Just get a small RC car/plane servo, and you'll be fine. Set it to push for 200 milliseconds, and then remove the push. Done!
The mechanics of making the servo have something to push against is probably going to be a worse challenge
Any gotchas I need to be aware of? I vaguely remember something about Ohm's Law from physics in high school, but otherwise I'm entirely new to this. So short of electrocuting myself (hehe, short. I made a punny), is there anything I should know?
The control signal for a servo can come from an Arduino pin. The actual power to the servo must come from a power supply, as it will draw more current than the Arduino can supply. Other than that, just go forth and experiment!
I'm all for the solid-state control method ... use your Arduino to control a triac (inexpensive full wave AC switch commonly found in dimmer switches) via an opto-isolating triac driver (moc3011 or equiv.) Both available from RadioShack.
Build it into a multiple outlet AC power strip ... later you can have Arduino check for "AC Power Good" so it doesn't turn on your PC during a power failure.
Then configure your PC to power-up after a power failure (Control Panel power settings or BIOS, I forget which).
No invasive computer mods, control multiple devices at once, very low power.
