Excel FORECAST function
I have never worked with spreadsheets more than this semester. I usually find myself using spreadsheets 5-6 times per week. They save a lot of time and frustration (except when an order of operations error goes undetected for two hours! ), but recently I had a project in which I needed to interpolate data in an X-Y chart.
I had the discrete X and Y values (in this case current and frequency) plotted on a chart, and I needed to find the value of the frequency at a specific current (in this case current divided by square root of two - which is the "half power" passing through an RLC filter circuit). I thought there would be some easy way to do it - such as the TRACE function on a graphing calculator where the curve is traced until the desired coordinates are found, but after searching the help and online I found no such solution.
After quite a bit of digging, I came across this old post on the MrExcel bulletin board, in which someone needs this exact procedure and the response is "Look for FORECAST function.
The FORECAST function will do this interpolation for you.
=FORECAST(x, known_y's, known_x's)
where x is x-value for which you would like to interpolate and find its corresponding y, and known_y's are from your discrete set of y values, and known_x's are your discrete set of x values. x is a number, and the knowns are ranges of number (cells you select).
I found the function to give very nice results, at least for this application.
You didn't fool me, Facebook.com
There isn't nearly enough advertising on that web site to pay for the plane trips, rental cars, and sexual harrassment lawsuits.
Musikmeister
Since I moved my web development server to an old laptop running Linux back in June, I have had the machine that was Teighler sitting around. It had Debian, PHP, and Apache all ready to go...I looked at it and realized that all I would have to do is add Music Player Daemon, a controller for it, a sound card, and some more hard drive space and this beast would be ready to act a music jukebox!
I had an old SoundBlaster 16 card laying around. This card is OLD, it is one of the type with the controller for a CDROM on it, and it goes into an ISA slot. It is quite adequate for this application though, and it is compatable with Linux.
Noise was going to be an issue, so I added some dense polyester foam on the inner walls of the case to help shut out at least some hard drive squeal. I changed out the power supply fan for one that is thermally throttled e.g. the hotter it gets the faster it spins. The CPU fan was removed and replaced with a larger heatsink without a fan. Since this is only a P133, heat was not a major concern. That also means that energy usage will not be a major concern and the BIOS does have rudimentary power management features such as shutting off the disks after a certain amount of idle time.
There is an 8 GB disk for the software, logs, playlists, and such and a 20 GB disk for music files. These are just disks I had laying around. As long as you don't go ripping a whole CD collection to FLAC format, you can cram a heck of a lot of music into 20 gigs. If that runs out...there are two options: add another drive or use a networked drive. I can also listen to internet radio like RADIOSEVEN via this thing! Sweet!
I installed MPD and used the phpMP interface for controlling it via the web. I also installed an ncurses-based player (ncmpd) if I feel like running it via console. The machine is supposed to run headless through the network. Administration happens through SSH, song adding/deleting through Samba, and control through SSH or the Web.
Screenshot of the Web Interface
Front-On shot of the machine and my custom paint job.
Close-Up of the front bezel.
Rear end. The only necessary connections are AC, network, and audio output.
This "Musikmeister" (German for "Music Master" I believe) generally needs to be connected to an external amplifier, but the SB16 has an on-board amp capable of 2 watts/channel into a 4-ohm load. The internal amp and the line out can be used simultaneously.
Wireless Network Problems end up being some issue in the OS
Long Story Ahead. Is your network doing things like allowing local traffic but not Internet traffic? It might be the computer, not the network! I had some serious issues on WinXP Pro. Always try system restore!Most of my day today was spent trying to figure out a problem with my wireless connection...
It all started Friday night, when I moved my laptop and disconnected it from the hardwired network. I expected to be able to use wireless, and the laptop did connect to my wireless network like usual, and I could access files on the network server, etc. However, when the time came to get out on the internet, no dice...
There was absolutely no internet access. No Web, no FTP, no ICMP. Not even to an IP address (ruling out DNS issues). I went to the wireless router config page, checked everything again and again, and from what the settings were, I should have had Internet access!
Maybe it was the computer? I thought. I took the computer outside and briefly utilized a neighbor's open WiFi network to confirm the fact that it was connecting okay, and it was.
I reset the router to factory default, and that did nothing. I then thought "Maybe I need to upgrade or reinstall the firmware". Plugged my cat5 cable back in, typed http://www.iblitzz.com and there was nothing. Apparently the company, Blitzz Technologies, went down the tubes. Not a trace of them on the Web. After 3 hours of searching I found the same firmware file that was already on the router. I reloaded it and it didn't fix the problem.
I figured that the router was having some issue with routing traffic between the wireless interface and the WAN (cable modem). My solution to that was to use our trusty old Linksys BEFSR41 router as the actual NATing device and just set the wireless router up as an access point (so the WAN port would not even be used). The Linksys was already in the basement acting as a switch, so I decided to move the cable modem down there. After running to Lowes and buying new F connectors for the end of the cable (had to chop the old one off as it wouldn't fit through the hole in the subfloor. I tried to save it by making the hole bigger, but the drill bit ended up eating the coax cable along with an ethernet cable running in the same hole. I then had to splice the ethernet cable back together. Oh well, it only feeds my brother's Xbox 360), the cable modem was operational in its new home.
I got the Linksys up and running, changed its IP address range from the 192.168.X.X to my favorite - 10.X.X.X. The computers which are hardwired were operational once again.
After getting the wireless router converted to a plain old access point, I could see the network and connect to it...but STILL ONLY LOCAL STUFF! The next two hours were spent tweaking settings and constantly modifying the network topology, but NOTHING WORKED.
I had a PCI wireless card around and I put this in a computer and tried to connect to the network - AND IT WORKED, BEAUTIFULLY. But it still didn't work for the laptop!
It was something in the laptop...after checking and checking again, I did a System restore back to a day when I was SURE that the wireless worked. Sure enough, that fixed it! It seems like the culprit was something that happened after I set up the Microsoft Loopback adapters (described in the previous post). I set up a loopback adapter again, and it seems to be doing okay. I have the adapter disabled, though, untill I need to use it.
As for the time and effort used to move the cable modem, I wanted to do that anyways and get it in the cabinet with all of the other network hardware. I guess this just gave me an excuse and motivation to actually do it!
This web log post went through that wireless connection, beamed upstairs to the access point (old router), then to the Linksys through a 50' gray ethernet cable, then to the cable modem, out through the new F-connector, and on its merry way to Andreas where it rides on the almost never-ending, 7200 RPM, coal-fired carousel waiting to be flung off to people like you.
Samba Tunnel via SSH and PuTTY
After trying several methods to create an over-the-Internet backup of my computer, I have settled on the SMB/CIFS tunnel through SSH using PuTTY.
I needed a way to do the backup across the Internet so that when I go to Wilkes-Barre this fall, my computer data will continue to be backed up to a secure remote location (e.g. Somewhere near Selinsgrove). I have a 200GB Maxtor Shared Storage drive that interfaces via the network, and the only way that it exposes itself is using SMB and CIFS protocol. I use an awesome freeware program called SyncBack to do my backups and synchronizations. Syncback can work with FTP servers as well as local and network drives. Here were my ideas to run a backup from my computer, over the Net, to this Shared Storage drive:
- Syncback -> FTP -> SSH Tunnel -> FTP Server on Linux Box -> smbmount -> Maxtor drive
- Syncback -> FTP -> Mindterm FTP-to-SFTP Bridge -> Linux Box -> smbmount -> Maxtor Drive
- Syncback -> SSH Tunnel -> Linux Box just to route packets to Maxtor Drive -> Maxtor Drive
Option 1 was far too complicated and over-engineered and there were far too many things that could fail.
Option 2 I tried and it failed. Mindterm just kept losing connection with the SFTP system on the server. I think that maybe the old laptop that I am using as a server couldn't handle the load (I was testing on the LAN. When I am on the Internet, the maximum will be 3 Mb/s as our cable modem service has a 3 Mb/s download.)
Option 3 - I followed These Simple Instructions and it worked like a charm...and I didn't even have to reboot the computer! I tried this setup about two years ago for a remote access application and it didn't work. Why didn't it work? I didn't read the instructions all the way through! Always read the instructions...I've learned the hard way too many times!
It works beautifully over the LAN, I have a key set up on the server and PuTTY's "Pageant" program that keeps keys in memory. That way, Syncback starts PuTTY and the tunnel using a restricted user (backup) to run the tunnel, then SyncBack goes and does its thing.