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316  Using Arduino / Project Guidance / Re: led indication for services (on/off) on a linux machine on: June 06, 2013, 02:46:59 am
For wifi on the arduino, I like the RN-XV Wifly units, with the WiflyHQ library:
https://www.sparkfun.com/products/10822
https://github.com/harlequin-tech/WiFlyHQ

You will also need an xbee explorer breakout board to make the RN-XV module work with the 5v serial lines on the Arduino.

I would just have the server save the results of that bash script to a file on the PC (using that method I linked to), then have a a little python script or something on the PC send a packet to the arduino containing the service state. The Wifly HQ library has an example that shows how to listen for a packet, and searching for "wiflyhq and python" shows you how to send the packet.

The actual lighting of the LED is trivial and covered in the playground and example sections of this site (its pretty much the first thing you learn how to do with an arduino). Thats assuming a standard 5mm LED, higher current LEDs require a little more setup.
317  Using Arduino / Project Guidance / Re: led indication for services (on/off) on a linux machine on: June 06, 2013, 01:52:34 am
that seems more secure but the problem is i dont have physical access to the remote linux server...
any thoughts?

I think I read your post wrong. I assumed the local PC would be local to the server, not to you. I also thought you meant the PC would be talking to the server over wifi.

So let me try again. You have a remote server that you want to monitor. You have a local PC that connects to the internet via wifi, and to the server over the internet. Will the arduino also need to use wifi to connect to the PC, or will it be close enough to connect through serial/usb?

How secure will the PC be? Will it just sit somewhere secure most of the time, or will you be lugging it around with you?(assuming its a laptop) You could probably get away with just locking down the user that you use for the SSH session. Give it read permissions for that one file, lock everything else, strip it of program execution permissions, don't give it a home directory, etc. A VPN would probably be preferable to SSH.

You could use the same bash file idea on the server, and have it save the output to a file on the PC, using a method like this: http://superuser.com/questions/400714/how-to-remotely-write-to-a-file-using-ssh . Then you wouldn't have a constantly open incoming SSH tunnel to the server.

The local arduino could grab that information off the PC in any number of ways. I'm not familiar with telnet on the arduino, but there are many examples of sending data to and from an arduino via TCP or UDP packets. Depending on the amount of services you need to monitor, one packet could be enough.
318  Using Arduino / Project Guidance / Re: led indication for services (on/off) on a linux machine on: June 05, 2013, 05:34:57 pm
It might be more secure to plug the arduino into the server, and have it act as a small webserver. That way you wouldn't have to leave an SSH session open for long periods of time, possibly un-monitored. Most services on linux have some kind of status command that can be called via the terminal, so i'm thinking you could have a bash script that runs all those commands and saves the responses to a text file. That text file could be sent to the arduino over its usb serial connection. You might be able to open the connection to the arduino in the same script that polls all your services, if not a simple python script would do it. The arduino could display the results on a simple html page.

If you need an LED light at a remote location, a second arduino could parse the simple html page (or they could communicate directly) and light it. How you light it depends on the type of LED, it could be as simple as adding a current limiting resistor and turning it on with a pin, or you might need a transistor or relay for a larger LED.

My solution is a little overly-complex, but it would prevent any new attack vectors from being opened up.
319  Using Arduino / Project Guidance / Re: How to Begin 3D Landscape Measure/Mapping Project on: June 05, 2013, 12:46:57 pm
Could you modify one of those rotary laser levels? I have seen those used in landscaping before, and they are accurate to fractions of an inch. If building your own laser detector is too complicated, you could modify one of the handheld units that are designed to work with the level.
320  Using Arduino / Project Guidance / Re: GUI student attendance system on: June 05, 2013, 01:25:40 am
This seems like a rather rapid progression of concepts for a single course. We didn't get into GUI development until my third programming course, and anything involving physical hardware was a 300 level course.

People are getting snippy because, although you have written plenty of words, the only useful information you have given us can be summed up in two words: "GUI, and Arduino". You can either setup the GUI on the Arduino, or on a PC that the Arduino is plugged into. Either way, you will need to write the GUI yourself, there are no programs that will set one up for you. GUI design is a fairly high-level programming concept. Do you know any programming languages? C++, C#, Java, PHP, Python, anything? Do you even need any kind of advanced GUI, or is your instructor just expecting you to display some text on a 16x2 character LCD?
321  Using Arduino / Project Guidance / Re: Shower timer?? Trying to figure out if its possible on: June 03, 2013, 01:18:27 am
How old is your house? Most modern homes use nice 1/4 turn shutoff valves for the hot water, right before every outlet.

There are plenty of electronic shut off valves that could be activated by the Arduino, but you run into the problem of the kid just unplugging it or unscrewing the device.
322  Using Arduino / Project Guidance / Re: External housing enclosures for a PSU? on: May 31, 2013, 07:32:13 am
Bud has some cheap project boxes that should be about that size. I don't see any measurements in that link, but if its the same as the PSU I have, this box should be close: http://www.mcmelectronics.com/product/21-4810
323  Using Arduino / Project Guidance / Re: powering on a laptop on: May 30, 2013, 07:53:38 pm
I think I will have to go the brute force way since the computer needs to be completely off when it powers on. I am still open to suggestions though

If you're not opposed to opening up the laptop, a small SSR, relay, or optoisolator would let you simulate a button press. Also, some motherboards have a setting in the BIOS to power up when power becomes available (usually see this on servers so they come back online automatically after a power outage). If your netbook has that setting, you could control the power supply to it with the Arduino. Then you know it is consuming no power while off.
324  Community / Bar Sport / Re: Things you always wanted to know but never dared to ask on: May 30, 2013, 01:41:36 pm
Bootloader monitors the serial lines, if no re-load activity is seen, then a previously sketch is directed to start.
But why the sketch cannot be performed directly after reset (there's a few seconds lag, due to the bootloader loading the sketch) ? I read somewhere that this is possible by burning the sketch into the chip using the ICSP. What is the difference, fundamentally, in the chip itslef ?

It is my understanding that the delay in loading the sketch gives the bootloader time to check for the previously mentioned "re-load activity". If you burn the sketch directly to the chip, with no bootloader, it doesn't wait to see if a new sketch is going to be uploaded.
325  Community / Bar Sport / Re: Google Code is about to die. ( for a lot of us anyway ) on: May 29, 2013, 06:51:15 pm
Doesn't Google Drive/Docs have a much smaller file size limit?

No limit.  First 5 GB is free.

I just started a 4.37 GB upload.  I'll let you know how that goes.

Finished.  No problems.  5 GB free storage.  Support for very large files.

Quote
In theory, you could post infinite amounts of data on google code, as long as you called it all "open source projects."  (that's how I remember it.  I can't see the old terms of service any more.)

200 MB chunks (upload limit).  4 GB per project limit.

Edit: upload finished.

IIRC, the google drive upload limit is 10gb, so double the size of the current free account. Drive is going to be merged with Gmail (the update is currently rolling out to users) to give you a combined storage of 15gb for free.
326  Community / Bar Sport / Re: Google Code is about to die. ( for a lot of us anyway ) on: May 27, 2013, 01:48:55 am
I have a host and a unused electronics domain ... add some light advertising and I smell an op ... least for our type of projects

and jeez cr0sh, I pay half that

I have been thinking about setting something like this up for a while. I have the location and the hardware, but I have a bit of a cashflow problem right now. I have quotes for business class 50/5 connections and 100/100 symmetrical fiber. I have a rack containing 6 servers, 3 of which have 16gb of ram and dual quad-core CPUs that would be excellent for running VMs. Maybe someday....

I do currently have one co-located server with no bandwidth limitations. The connection is pretty slow though 1mbit down, 2mbit up.
327  Using Arduino / Project Guidance / Re: arduino eclipse and serial communication on: May 13, 2013, 01:25:21 am
i use eclipse to programm to arduino.I had to reinstall the whole package these days.

I installed the tm plugin for terminal and rxtx also.

when i try to connect to the serial port i get error that another unknown program uses the serial communication.Do you know how to solve this?

This sounds like a question that should be asked on the Eclipse forums.
328  Using Arduino / Project Guidance / Re: monitor 12 vdc automotive battery used to start backup generator on: May 07, 2013, 02:05:17 am
You would also need to disable the trickle charge at the time of the voltage measurement, otherwise you're just going to get 14v 100% of the time.
329  Using Arduino / Project Guidance / Re: Heat Protection on: May 06, 2013, 02:06:13 am
This just seems like a really bad idea, unless the idea is to turn your arduino into slag.

Perhaps something like this would work better:
https://www.sparkfun.com/products/251

Or an infared sensor?
330  Using Arduino / Project Guidance / Re: I want to build: configurable fan controller + 3 thermal sensors on: May 05, 2013, 05:14:55 pm
Ok
Go it! smiley
Cool idea! Thx!
I think that could be the way to go...
Now just need to get my LianLi case and figure out, how to make arduino to helm me to reach the goal

An arduino can easily take temperature readings, control fans, and turn a compressor on/off.
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