Mar 31

Expo Time!

The Lab will be closed on Saturday, April 12th, 2014.

Lou’s headed off to New York for the Northeast Astronomy Forum:

Brett & I are headed off to the Cabin Fever Expo to move our cnc mill project forward & learn more about the world of hobbyist machining:


Feb 16

CNC Mill Progress

CNC Lathe 1

CNC Mill Progress!

Much progress was made today at the lab.  The DC brushless motor controller that Dave found, ordered and installed in the CNC mill chassis was finally wired up to be tested.

What CNC mill?

The Tech Media lab was gifted a CNC mill months ago.  It’s a wonderful piece of equipment that can gnaw away at various metals, wood and plastics under the control of a computer.  The device that was donated to us was only partially functional (which is probably a contributing factor to it finding itself into our hot little hands!).
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Nov 24

I/O Expander Project – Parts is parts

So, now that we’ve got a rough idea of what the I/O expander is going to do, what next?  After fiddling around with some rough block diagrams, it’s time to investigate the major components that we want to use in the design.  Got to start somewhere..

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Nov 21

I/O Expander Project Introduction

I’ve decided that I’m going to design and build an I/O expansion board to address a particular need that I have. You’ll all get to follow along and watch during the process. Who knows how long it will take?

5210976626_cea1229582_bOne of my hobbies is astrophotography. I live out in the country, and have a roll-off roof observatory about 200 yards away from my house. I’d like to add some monitoring and control capability to support my activities there. I need some additional security features, as well as some automation capability, including the ability to control a motor that might be installed in the future to open and close the roof. There’s also a need to switch 12VDC power to the telescope mount and some accessories, with the ultimate goal of being able to operate the whole system remotely.

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Oct 10

Experiment and Learn: how fast is electricity?

How fast is electricity?  A lab experiment

Have you ever wondered: how long does it take the electricity to get to from the light switch to the light bulb when I flip the switch?  Not very long, but not zero time, either.  In fact, with a bunch of wire and an oscilloscope, we can measure how fast the electrical signal travels through wire.

What’s the experiment like?

  • We have something that makes a periodic digital signal, a pulse every so often — say about every 10 milliseconds or so?   We want the pulse to have a nicely well defined edge that we can detect and measure.
  • We need a long piece of wire.  We can take a length of 4-pair CAT5 ethernet cable, and at either end of the cable, connect the pairs in series so that the signal actually travels over the length of cable 4 times, once over each pair of cable.
  • We’ll take one end, and connect it to our pulse generator.
  • We’ll take the other end, and connect a 100-ohm resistor across it.  (For the geeks in the audience, this is to match the impedance of the twisted pair cable and avoid reflections that will foul up our measurements.)
  • We need a two-channel oscilloscope, with a reasonably fast sweep time, say 10 microseconds per division.
  • We’ll loop our cable around such that both ends are sitting next to each other, and then connect one probe of our oscilloscope to the pulse generator where it connects to the pair of wires at the end of the cable.
  • We’ll connect the other channel of our oscilloscope to the far end of the cable, across the 100-ohm resistor.
  • Turn on our pulse generator.  The pulse generator could just be an Arduino digital output, with a simple program to toggle the output on and off rapidly.
  • Now we measure and learn!


How does this work?  We need to first understand how an oscilloscope works.  This is a neat bit of test equipment that lets you look at signals in an interesting way: in the time domain!  No, it’s not a time machine.. not really.  But it does let you look into the past because it measures the voltage over time, and graphs it on the display.  Huh?

Think about a volt meter.  You can connect this to your 9V battery and when you connect the probes up (and you have the right scale selected, you’ll see something very near “9” on the measurement display.  This could be a digital readout, or it could be an analog meter sweeping across a scale.

When you connect up your volt meter, you see the voltage measured right now on the display.  If the voltage changes, then the readout changes on your volt meter.  But unless you have a really good memory and good eyesight, you can’t accurately remember what all the different readings were on a voltage that changes rapidly..

This is where an oscilloscope comes in!  On the screen of an oscilloscope, you’ll see a trace being drawn from left to right, moving across the screen.  The rate that the trace moves across the screen can be selected – for example over a range of moving once across the screen per second to moving once across the screen in a millionth of a second!  There’s usually a well-calibrated timebase in the oscilloscope that moves the trace across the screen at a precise rate.

Ok, so the trace moves from left to right at a know rate, but it is also positioned vertically on the “Y” axis according to the voltage being measured at the input.  And the vertical scale is also calibrated, over multiple ranges.  You could set the scope where the entire vertical distance corresponds to a range of zero volts to 100 volts.  Or maybe zero volts to 10 thousandth of a volt and ranges in between.

So if you have an input voltage that’s varying, you can set up your oscilloscope to sweep at the right rate base on how fast the signal changes, and with the right vertical voltage scale to examine the signal as it changes over the range.

An oscilloscope can have multiple inputs – like having more than one voltmeter at a time.  They have to share the same sweep speed, but the voltage range can be independently adjustable.

So to measure the speed of electricity, we look at the signal at the origin (our pulse generator) with one channel of the oscilloscope, and we look at the voltage at the other end of the cable with the other channel.  We should then see our pulse being measure by both channels, but they will be offset from each other on the oscilloscope display. Since we know what the speed speed is across the display, we can measure the difference between the two offset pulses and compute how many microseconds delay there is.  That, couple with our knowledge of the length of the cable will allow us to compute the propagation speed per meter of cable.

Other (real or thought) experiments:

  • Does the pulse travel the same speed though different types of cables (e.g., twisted pair ethernet cable vs. coax cable).
  • Does electricity travel the same speed as light?  How could you test this?


Oct 10

Intern opportunities with the Mount Union Tech Lab

Help Wanted!

The tech lab is starting an Intern Program, and is looking for participants with an interested in technology, Linux, electronics.  We want motivated participants that can take on some meaningful, real projects and who will gain experience and learn in the process.

We are presently considering high school students for our Intern program.  Are you looking for an interesting Community Service project, where you can learn some new things along the way, get some experience for  your resume, and make a difference for your community?  Consider us!

What would an Intern do with the Tech Lab?

That’s a great question!  We’re a newly formed charitable non-profit corporation with a mission to educate.  There’s lots to do, no busy work.   Just a list of the kind of things we’re thinking about:

  • Think our web site looks ugly?  Yeah, it probably is!  Want to learn about the WordPress system we use for this site, and improve it?  Here’s an opportunity to do so.
  • Have you heard about these Arduino micro controllers?  Raspberry Pi computers?  They’re really cheap and there’s all sorts of fun stuff people are using them for.  We have a some of these in the lab, and other peripherals and the free development tools for them.  How about you build a cool project, and document your steps throughout the process on the web site so that others can follow along behind you?
  • Do you have an interest in electronics?  Ever want to build some small electronic widget; from scratch — not just plugging boards into a PC?  A longer duration project might be to conceive of some fun little project, develop an electrical schematic for the device, prototype it (and maybe write some firmware).  Then using free tools, design a printed circuit board, have it fabricated, solder the parts on the printed circuit board and then package it.  Oh, and document your progress on the web site so that others can learn from your experience!  We’ll even teach you how to solder and use a soldering iron (hint: don’t grab the hot end!)
  • If electronics isn’t your thing, but you surf the web and know about this Internet thing — maybe you can help us in our efforts to support the Mount Union Community Library.  They have public workstations in their library running Linux for the use of their patrons.  The library can always use some additional support for their patrons as they use the Internet, and for updating and maintaining the content on their web site.
  • Are you a Linux-geek!  The Tech Lab has a customized version of Mint Linux that we’ve assembled and installed on the Library’s Patron computers.  Mint Linux runs well on older computers that have been donated to the library, and don’t seem to have the virus infestation problems that Windows has.  Our version has a “patron kiosk” mode that automagically resets the state of the “patron” user on these public workstations as new users start to use this shared computer.   How would you like to help us enhance this distribution of Linux for the library’s use or for other public, shared workstations?

That’s just a sample of the sorts of things that the Tech Lab needs help with.  There are surely many others, and we’d love to hear about ideas of your own.   The common themes are

  • Our educational mission.  When you do something interesting and creative, we want to capture the process you used and the result, and have it be available to others that come later to learn from.  If you make a widget, record how you made it so that others can build on that work.
  • Service to the community – the clearest example is our support of the Mount Union Community Library’s technology needs.  The larger community needs help, too.  Can we bring free Linux operating systems for our friends and neighbors in the community to use on older computers that won’t run Windows 8?  What about when Microsoft stops supporting Windows XP early next year; is there an alternative environment that’s safe and secure that can be used instead?

How would this work?

Our Intern program is brand new, so we’ll be figuring that out as we go along.

We are physically located in Mount Union, in the Borough building above the Mount Union Community Library.  However, we are open to participants anywhere nearby.  Our initial focus is Huntingdon County, but we have an open mind.  Much or most of the work that needs to be done might be done from your home?  If you have a computer available and Internet access, you can work on the web site from pretty much anywhere; heck, the server itself is in Baltimore!  Some programs might require physical presence; e.g., supporting library patrons in the library probably requires you to be there at the library in Mount Union.    We are unable to supply any transportation, so participants will need to arrange for any that is needed.

Much of the work we do uses computers as tools.  You can use a computer at the lab, or one of your own at home.  A central part of an Intern’s activity will perform is documenting the interesting work that you do.  This will help the Intern document the effort they’ve invested for their Community Service requirements as well as likely being a part of the “deliverable” itself so that others can learn from your work.  So while we won’t be grading your spelling and grammar, we do expect high-school level writing skills.

You”ll be collaborating with some members of the Tech Lab who will give you direction and assistance when needed.  How we do that is yet to be determined; either in-person meetings on a regular basis or we can use various online collaboration tools as appropriate.  Do we need a wiki?  (Maybe that’s a great project, to set one of those up?)  How about Google Hangouts for real time video conferencing?  Or Skype?  Or maybe even an occasional phone call.

The ideal participant will not need constant monitoring and direction.  They should want to engage in a project such that the Intern and the Tech Lab mutually benefit from the experience.  The Intern will have an opportunity to learn new things that are already of some interest, and the Tech Lab benefits by having our mission advanced.

We both invest mainly our time, probably the most valuable resource of all.   Neither the Intern or the Tech Lab should think that our time is being wasted!

Let’s have some fun!  We have all sorts of interesting tech toys and junk at the lab, just begging for someone to put them to use.

I’m interested, so what now?

If being a Mount Union Tech Lab Intern sounds like something you’d like to do, then drop us an email at and In about a page of text or  tell us a little something about yourself and explain what you’re interested in doing as an Intern at the lab.  We don’t have a fixed schedule, so first-come, first served!

Tell us a little about yourself, your background in related areas and an experience you might have.  “Experience” also includes relevant or related hobbies and interests!   Do you have Linux on a computer at home you play with? Have you built anything with a soldering iron?  Do you write software for fun?  Do you have an account on GitHub?  Have an amateur radio license?  Can you help others understand computers, because computers are afraid of you and not the reverse?

Your document is also going to be used as a writing sample since we’d expect you to be able to communicate in the written form effectively to publish the results of your work.  So think, write, proof-read and send us your thoughts.

We have not yet determined how many Intern positions we’ll have open at the same time, and that number could vary based on the applications we get and the areas of interest.


Oct 07

Firefox Print Delay in Linux

We provide technical support for the community library, volunteer supported since Huntingdon County closed the branch in 2010. They have (4) 2009 HP desktops, (3) 2008 Dells and a 2012 HP desktop that are available for public use. They also have a couple HP laptops the volunteers use for barcode book checkout, along with HP 4100 & Brother MFC lasers.

We added a BSD PFSense firewall built on an old Dell I had sitting around and Lou arranged the ports to keep the internal network more secure while still maintaining publicly available open wifi. We’re using OpenDNS to minimize online mischief, seems to work.

Last month we replaced Windows XP with Linux Xfce on the workstations for public use in the Library. Lou came up with a way to have a fresh session each time a patron logged in. We thought ‘mischief managed’, no more issues with the multitude of virus & adware issues in Windows and no more risk that a patron’s session details could be seen by anyone else.

We had set up a single workstation for people to try out and the feedback was positive. We made some minor changes, adding a few more popular programs, setting up the Library’s HP4100 for printing and then updating the image. Clonezilla was used to make a master on a usb drive & we began changing machines over.

For some reason the HP desktops would not cooperate with the usb stick booting up & running Clonezilla although the Dell’s did. Burned a bootable Clonezilla dvd & installed the images. Everything seemed to work just fine, printed test document from LibreWriter, another from Google Docs, it wasn’t speedy but it seemed okay enough & called it a day.

About a week ago we were told it was taking hours to print a picture. Looking into it more closely, getting beyond the stuff that happens like people clicking print repeatedly, it looked like a Firefox issue. LibreWriter & Chrome printed in less than a minute, what you’d expect with a laserjet 4100. Firefox print jobs took 7 or 8 minutes for a single web page.

While I did find different posts about print issues in Firefox, changing the print string in Firefox didn’t make any difference. As Lou & I played with the printing, he was watching the processes. It looked like both Firefox & Chrome were doing some pdf to postscript process using ghostwriter. Chrome was doing it more quickly, Firefox much more slowly.

Reviewing the setup in cups & toying with the idea that this was some driver issue, I started lobbying for a pcl driver. It’s an HP laserjet & I’m an ancient Windows guy & pcl is just so . . . normal to me. Lou is a Mac person & a postscript fan & he decided he was willing to try a pcl “pickle” driver. Bingo bongo. Home run! LibreWriter, Chrome & Firefox print a one page job so fast that you can’t catch the process. Vrrrroooooom.

We modified cups on the rest of the workstations to use the pcl (no postscript) driver. Problem solved.

Why was it taking so long to render a postscript job? The 4100 claimed to have postscript. Chrome & Firefox probably send a pdf sort of thing to cups . . . for now we’ve decided to just back away and leave it at “something” was grinding pretty hard to produce a postscript job, especially from Firefox.


Sep 30

Hello world!

It’s taken some time amid the activities of setting up a new “Tech Media Lab” to get to the website.

We think a “Tech Media Lab” is a modern version of computer & electronics club. It’s much different from “Consumer Computing”, whatever that may be. If you combined a Maker Space, Hacker Space, Imagineering & Inventioneering Mash Unit, Art & Light Studio, added abundant curiosity, enthusiasm for learning you’d get some sparkling gem with many facets.

We’ve brought together a range of project learning opportunities, from our cnc Bench Mill, the very low energy light emitting ceiling to the flying r/c toys, a healthy collection of electronic components & sensors and a growing collection of powerful micro-controllers.

There are now half a dozen workstations available, Mac, PC & Linux, a big closet overflowing with donor electronics and more.

The lab is open to the public 5 days a week. On Tuesdays, Wednesday & Fridays from 5-8pm and Noon to 5pm on weekends.

For more information contact us at or call (814) 808-5221 . . .

Sep 30

cq cq Hello cq

By the age of thirteen I was pleased, proud to be awarded a General Class Amateur Radio License. I was really, truly a “ham radio operator” and I loved it. With a dozen boys my age, we had an amazing time, a great club, spending any free moment we could “on the air”.

By that point I had spent so many hours keying morse code on a jeweled, side-swiper paddle keyer, I could run with the big dogs. I had developed my own unique sound, a “lilt” that was recognizable in the fast paced stream of dots & dashes. That let me explore the world, eventually collecting confirmation cards from most every country in the world.

Little did I realize at the time that the ‘old man’ who taught us about physics, especially as it applied to radio waves & propagation, taught us all a great deal more. He was every day of his 60+ years and had taught Physics for many of them. He shared much of what he’d learned from life, no doubt sanitized for goofy 13 year old understanding. To this day I absolutely know where I learned to love the fine art of Muskie Fishing, how to tie knots that wouldn’t cost you a trophy fish & properly sharpen multiple treble hooks on a 9″ long lure. I was never to become a “fair weather fisherman” and I was always to have a curiosity about all things technical & be willing to learn.

Among the lessons on building heathkits & more, learning ohm’s law, the various physical properties of things, he wove in stories about the rest of life as he’d experienced it. The bittersweet melancholy of falling in love with someone who didn’t fall in love with him. And never meeting another. How he came to America from Ireland by way of the British Navy. His satisfaction starting one of the very first commercial radio stations in America and creating the programming, the choices in music and the very essential “Farm Report”.

I have always felt some obligation to pay it forward and doubt very much that I will. He was a better story teller as I recall, had much more depth of understanding in many areas and that was a very different time. A very different time . . .

If he were here now I think he would be even more frustrated about “the limitations” than he was back then. And he was acknowledged & appreciated by both parents & educators and granted considerable freedom to teach toward “knowledge”. That’s what made the General Class license so valuable to me, I had really learned what it meant to be considered General Class, not just to answer the test questions, to be a member in good standing in the world of ham radio with a greater understanding of the world than “just” ham radio.