The Life of Kenneth

How to Carbonate Pretty Much Anything

2012-01-27T20:00:00.000-08:00

Carbonated apple juice.

This has been a project I've been wanting to do for several years, but I've always lacked the confidence to try it until after watching Ben Krasnow do many things of the same ilk. The concept is relatively simple; soda gains its bubbly taste and much of its acidity through a process called carbonation, where carbon dioxide is dissolved into a water-based solution. Gases are actually always soluble in water (which is why fish don't drown), but if you raise the pressure of the gas pressing down on the water (or cool the water), progressively more gas will dissolve into the water. Conversely, if you lower the pressure, the dissolved gas will come out of solution and bubble out.

Here's a fun experiment: Fill a drinking glass with tap water and leave it somewhere undisturbed for several hours. Notice how lots of small bubble of gas form on the inside of the glass. Why is that?

So soda is carbonated by dissolving more CO₂ into it than naturally exists in the Earth's atmosphere. This causes the soda to bubble once you release the pressure in the bottle, and the carbon dioxide actually combines with the water to form carbonic acid:

The chemistry really isn't so bad; take something water-based, add excess CO₂, enjoy the pleasurable bubbly and tangy sensation you traditionally associate with soda and other carbonated beverages.

Doing this at home is very easy, but potentially rather dangerous. Getting high pressure CO₂ isn't too difficult; you can go to the grocery store and buy dry ice for about $1 per pound. Dry ice is solid CO₂, so as it sublimates into a gas, it vastly expands (there is an almost 800x volume difference between CO₂ as a solid and a gas), but if you instead trap it inside a pressure vessel, it becomes a high pressure gas.

Now you just need to build a pressure vessel to contain the CO₂ and whatever you want the CO₂ to go into.

There's a hitch; you can't just drop a chunk of dry ice into a plastic bottle with some water. Well, you can, but this is a traditional past-time done by teenage delinquents due to the fact that the bottle inevitably explodes. We don't want our pressure vessel to explode. We want to hold it at something like 30PSI for awhile and then be able to pour out our freshly carbonated beverage. This is the problem that has previously always scared me off of this project. With Ben's help, I've managed to come up with the beginnings of a solution to this.

Meet my pressure vessel. I built this out of 3" schedule 40 PVC pipe, a couple pipe fittings, a 100PSI pressure gauge, and a needle valve drain cock. I horse-traded the pressure gauge from my ever-supportive father for helping to clean up his shop this winter break, but was able to buy the rest of it at an Ace Hardware for about $25.

Building the chamber out of 3" schedule 40 PVC is important. Each diameter and schedule of pipe has a different operating pressure, which is the highest pressure at which the pipe is still safe. larger schedule numbers indicate higher pressures, so if the 260PSI operating pressure of 3" schedule 40 was too low for this, we would move up to schedule 80 or schedule 120 NPS, at the expense of higher cost and it being much more difficult to purchase SCH80 or SCH120 pipe retail. The PVC parts needed for this should all be easy to find in your local hardware store's gardening or plumbing sections:

16" of 3" SCH40 PVC pipe. Many hardware stores will custom-cut this to length for you if you ask nicely. I ordered 16" to give me a final chamber volume of 2L, but feel free to build your chamber as big or small as you like.
1x 3" slip end cap. This is the fitting in the bottom center of the picture above, and is to be cemented onto the bottom end of the pipe.
1x 3" slip to female NPT coupling. You can get 3" pipe with pipe threads on it, but it's often much easier and cheaper to use slip fittings everywhere except where you need your access port.
1x 3" male NPT plug. This is a threaded plug which I installed the pressure gauge and needle valve into, and which I take on and off to refill the chamber between batches.
Teflon tape - This is often called plumber's tape, and is used to seal the threaded joints between the pressure gauge, needle valve, plug, and NPT coupling.
PVC cement and primer - The slip fittings can all be permanently joined, since the threaded plug can be removed to fill, empty, and clean the chamber.

This project was the first time I've ever dealt with NPT, or National Pipe Thread. This is a special pressure-tight thread designed for pipe fittings, which has a distinctive taper to it. As you're wandering through the hardware store, pause for a moment to appreciate the threaded pipe and notice that it gets skinnier towards the end. This gives the thread much more compressive force when it's screwed together than normal straight threads, which causes it to be pressure tight. Fun fact: NPT tapers off at 1° 47′ 24″, which works out to be an inch for every 16 inches of thread, and a crazy small angle.

The pressure gauge and needle valve are really important. Since the CO₂ is trying to expand to 800 times its original volume, it is very easy to add so much dry ice to the chamber such that we will go well beyond the 260PSI limit of the pipe, and create a very impressive, if unfortunate, bomb. The pressure gauge lets us monitor how high the pressure gets inside the chamber, and the needle valve allows us to just crack it and bleed off CO₂ as slowly as we want.

Fixing the valve and gauge on the plug does require access to a fairly well stocked machine shop. Pulling out my copy of Industrial Presses Machinery's Handbook, I was able to find tables for how large of a hole to drill for both the 1/8" and 1/4" NPT taps I need for these two fittings (28th ed, p1863, table 1b, 1/8" NPT - drill letter Q, 1/4" NPT - 7/16"). Drill, tap, apply teflon tape, screw in, enjoy.

Now for the actual contents of the chamber. There are several possible sources of high-pressure CO₂, but probably one of the simplest is dry ice. You will need to be a little deliberate to make sure you choose a grocery store that carries dry ice (maybe one in five Safeways. In Davis it happens to only be available at SaveMart), but once you find one that does carry it, you just need to ask the cashier for 1-2 pounds of it when you're checking out; they'll go unlock the box, weigh out a chunk, and bag it for you. You'll want to break up the dry ice into smaller pieces, since each batch isn't going to use that much dry ice, and it'll go faster with small pieces.

As far as exactly what you carbonate, the sky is pretty much the limit. The classics include water (optionally with flavored syrups to make Italian sodas), fruit juices, and reviving flat sodas or beer, but anything with a high water content works. I sized this chamber rather deliberately such that I can easily fit apple and orange slices in it. The carbonated fruit comes out with a very intriguing sparkling aftertaste. I only let the fruit soak for ~20 minutes, which wasn't quite long enough (they went flat rather quickly), so solid fruit would probably be something you'd want to pressurize several hours early, get the chamber stabilized, and just let it sit until ready to serve.

Fundamental problem with this setup

Generating high pressure CO₂ gas from dry ice is fundamentally a problematic affair. In the ideal world, I wouldn't have anything to do with the stuff and use a commercial gas cylinder and gas regulator to charge the chamber, but those are expensive.

The real problem is that it is very easy for the dry ice to get away from you, particularly when you're using it to charge liquids. Water has a very high thermal mass, which is why dry ice sublimates so quickly when you drop it in the punch bowl during Halloween. Unfortunately, the water tends to freeze on the dry ice, cause it to sublimate slower. Once the chamber finally reaches your target pressure and you start venting it, the ice will often crack off the dry ice and you'll see the chamber start to rise in pressure quite rapidly. During one of the batches, I cracked the needle valve when the chamber reached 60PSI, and in a matter of seconds the pressure inside the vessel pegged above 100PSI before I was able to spin the valve wide open.

A possible modification to solve this icing issue would be to separate the solid dry ice from the water entirely. Building a second (much smaller) chamber to sublime the dry ice, and then pipe the high pressure CO₂ back into the main chamber, would be much easier to control. You would still want the dry ice to be sitting in some sort of liquid to act as a heat source, but you would then be able to use something with a much lower freezing point, such as high proof ethanol, and could even make the secondary generation chamber somehow detachable to charge multiple vessels.

In the end, I would still rank this as a rather difficult and dangerous project, and you can buy carbonation tools retail which are much much safer than this, but I found it an interesting way to spend an afternoon. Anyone else in Davis want to have a sparkling fruit juice party?

Weather Alerts Through Prowl

2012-01-19T20:00:00.000-08:00

The fun with Prowl continues. After getting it running on my Chumby and WRT54G, I was digging through the Prowl Forums looking for other interesting applications when I found a post by acrollet showing how he has his server watch for severe weather alerts from weather.gov and send them to him as push alerts. I thought it was a good start, but he crammed the whole thing into his cron table as one line, which is a style I just don't like, so I've rewritten his script with some improvements.

How this alert works is that every hour the cron scheduler on my alarm clock downloads a chunk of XML from weather.gov which they make available for every region across the US. So, for example, Yolo county has the county code CAC113, so I have the script hourly download http://alerts.weather.gov/cap/wwaatmget.php?x=CAC113 and check to see if there is a new severe weather alert for Yolo county.

If there is an alert, and it's at all different from the one seen an hour ago (which the script stores in /tmp/weather.CAC113.old.txt), then the script uses some grep, awk, and tr magic to extract nice clean summaries and an event name for the alert. It then uses the typical curl request I figured out before to fire off the push alert and it blows up my iPod with weather alerts.

One thing that you might notice about the script is that I have all of the heavy lifting done in a single function (queryWeather()), which I then call repeatedly, passing it the zone code and my API key. I did this such that it will be very easy to add or remove zones I want to watch, as well as add friends who also have Prowl onto various zones that they're interested in (I'm toying with having this automated through a web form).

I have this installed on my Chumby's SD card (/mnt/storage/scripts/), but this should run in any decent unix environment.

Script code:

Posting Prowl Messages from BusyBox

2012-01-18T13:00:00.000-08:00

Yesterday, I showed how to send Prowl notifications to your iOS device from a full featured unix shell. Unfortunately, more and more devices are now running Linux, but lack the full featured shell needed to use curl or wget to create POST requests over SSL. This is because many devices, such as WRT54GL routers, NASes, etc, don't really ever need a fully featured user space, so why waste flash storage on utility features which won't be used? You will find most embedded Linux devices are based on a project called BusyBox.

BusyBox is a stripped down replacement for the traditional GNU user space found in most modern unix environments. BusyBox implements all of the basic shell utilities such as rm, ls, touch, vi, awk, sed, et cetera, but you will find that most of these utilities are a far cry from their GNU equivalents, only implementing the bare essentials to have a functional Linux system. For example, GNU wget has more than 100 available options which you can use to change the behavior as to how wget downloads files or forms requests. BusyBox wget has seven, and unfortunately, these seven available options don't happen to include the "--post-data" needed to have wget form the POST HTTP request we need to use the Prowl API.

So we've got a real problem. Prowl's API works through HTTP POST commands (preferably over SSL, but no longer required), but BusyBox's wget lacks the "--post-data" option. So what the heck do you do?

The obvious answer is to port GNU wget, curl, or even write your own utility to create HTTP POST requests and send them down the line. HTTP is a fairly simple protocol, and this shouldn't be too big of a deal. Heck, if you're nimble on the keyboard, you can type in HTTP requests by hand using netcat.

I didn't like that. BusyBox gives us such a simple but powerful set of tools. Why go through all the pain of porting something over to a MIPS processor when you can do it with the tools you already have?

So what are we trying to do with a HTTP POST command, really?

HTTP is the protocol used to deliver information over the web. When you type in a URL (such as http://www.google.com), you are telling your web browser to generate a HTTP GET request and to send it off to whatever server is specified by the URL. HTTP POST requests are very similar, but have extra information in them beyond simply the URL, most often used to pass information back to the web server after you fill out web forms.

But POST requests aren't the only way to pass information back to web servers. We can use GET requests as well, by appending the information to return to the end of the URL after a question mark. So, for example, we want to pass to the page http://api.prowlapp.com/publicapi/add our request which includes our apikey, application, event, and description. This would end up as a HTTP request that would like like this:

http://api.prowlapp.com/publicapi/add?option=value&option=value&option=value

After the URL, a question mark begins a number of option=value pairs, which would include our apikey=XXXX, application=WRT54GL, etc. This isn't as nice as POST requests, because we're more limited at to which characters we can use (which we'll get into later on in this post), and these long ugly URLs tend to lead to users accidentally leaking information more often than POST requests, but the brain dead wget in BusyBox MUST handle GET requests, or else it really wouldn't be a very useful utility at all.

So what's the big deal with building this special GET request with all our info? Couple shell variables, string 'em all together using a ? and a couple &s, and you've got your URL, right?

URLs are very limited at to the characters they can use in a request. This is why you'll often see your browser replace such characters as spaces in a URL with %20, which is the ASCII hex representation of " ", because the space otherwise looks like the end of the URL. So once we generate our long string of option=value pairs, we need to encode them to avoid using any illegal symbols when forming the URL, such as spaces, new lines, %, ~, ^, etc.

This URL encoding can be almost completely accomplished just using a tool called sed, or "stream editor." Sed operates by you feeding a string of text into it, give it a set of conditions where to replace one thing with another, and then it outputs this edited stream of text.

For example, to encode all the spaces in our request, we need to replace them with their ASCII hex value of 20. This is done by giving sed the command s/ /%20/g, which says to substitute every instance of " " with %20 through all of every line. Put together a long boring list of all of these needed sed commands, and we're 95% of the way there.

The one piece of the puzzle missing with using sed is that sed doesn't consider new lines. Sed operates on a stream one line at a time, which it uses new lines to split the stream into, but it doesn't actually see the new lines traveling through the stream. So after we convert all the other special characters into their hex equivalent, we need to somehow replace every new line with %0a. To do this, we use a different tool called tr ("Translate"), which you can give one set of characters to replace with another.

For example, if you were to give tr a-z A-Z, it would substitute every lower case letter in the stream with its corresponding upper case letter. But we don't need it to do that; we just need it to replace new lines with %0a...

Unfortunately, in a word, it can't. Tr can't replace a single character with multiple characters... If only we knew one that did... Hmmm...

What about sed? We could have tr, which can see the new lines, replace all of the new lines with some special character which sed CAN see, and which is unlikely to already be in the stream, and then have sed replace each of these characters representing new lines with the needed %0a. Luckily, we have a whole set of characters which we know aren't in the stream anymore, because we just had sed do all this work to encode spaces and tildes into their hex equivalents.

I arbitrarily picked tildes, but any special character would do. Take the otherwise scrubbed stream, feed it through tr '\n' '~' to replace new lines with ~, and then feed that through sed again with the single command 's/~/%0a/g' and we have an entirely encoded URL, which we can pass on to wget to post to Prowl from our wifi router.

Pretty awesome, if I may say so myself. In the example code below, I have my router generate a little report including it's CPU load average and file system usage, but you can replace those two lines feeding text into $CACHE with whatever you like, or even have the shell script take the message content as an argument through the shell. Tomato (and likely most other third party firmwares) makes it real easy to trigger scripts on a regular basis, or even when someone presses the button on the front of it.

Don't forget to insert your API key at the top of the script.

Shell code:

Edit: I probably should have reread the RFCs and Wikipedia pages on HTTP before publishing this. I believe I've now fixed most of my confusion between GET and POST requests.

Sending Prowl Notifications from Linux

2012-01-15T09:00:00.000-08:00

More than a year ago, I set up my lovely Chumby alarm clock as a web server (go check it out!), which I find useful every now and again for quickly hosting small files. Unfortunately, even after upgrading it to an 8GB internal SD card, between all the files I dump on it and my poor log rotation schedule on it, it sometimes manages to run out of file system space and gets kind of cranky.

I recently purchased a copy of Prowl, which is a growl notification app for iOS. Growl is a universal notification system which I'm planning on building into some embedded hardware projects I'm working on, but I figured that while I had already bought the application, I would see how many other nails I can pound in with this hammer. Turns out, this was a fairly simple application of said hammer to problem.

I wrote a simple shell script and installed it on my Chumby such that every morning at 8:30AM I wake up to a message on my iPod informing me on how my Chumby is doing. This is done by generating the report via several lines of Bash, storing it in a temporary file, and then passing it along with my Prowl API key to one magic curl command, which you can see at the end of my code:

Shell code:

To get this working, you'll need to copy this shell script onto your Chumby, and then add a line to your Chumby's crontab to schedule it to run at the desired time. You'll also need to replace my API key with one of your own.

Now, obviously since this is just using cURL to post the notifications, you can run this script in any environment which supports curl, be it almost any Linux environment, OSX, or pretty much anything else.

I found a forum thread on cocoaforge useful while putting this together.

This can also be done using wget instead of curl, if you prefer. Note that the version of wget on the Chumby doesn't support SSL, so you'll need to drop back to http instead of the suggested https:
$ wget --post-data 'apikey=2541[snip]4d77&application=wget&event=Test message&description=I can use wget' -O - https://api.prowlapp.com/publicapi/add

Pogo Your Programmer

2012-01-12T15:00:00.000-08:00

A lot of my projects are getting to the point where I'm going to be flashing them with firmware once and then installing them to be never flashed again. This means soldering all the ICSP headers in seems a little silly, but I found a better solution.

Turns out the pogo pins sold by AdaFruit fit in female connectors, so I (carefully) pressed six into my USBtinyISP and bam; bed of nails programmer. You have to be very careful inserting them; I managed to destroy two pins in the process, so I'm dedicating a whole programmer with these pins, and switched to a spare for main development, because you don't want to be swapping these in and out.

Book Giveaway - Benchtop Electronics Handbook

2012-01-09T18:00:00.000-08:00

Hope everyone is having a good start to their 2012. I've decided that my new years resolution is to try and clean out some of the free stuff I get, so I'm going to experiment with giving stuff away on here.

The first piece of nerdy goodness up for grabs is a copy of Veley's Benchtop Electronics Handbook. This is a good introductory text on electronics, with 260 educational blurbs on everything from electrical units to basic mathematics to boolean algebra to Karnaugh charts. I'd call it the reference book for the beginner; the second book you'll want to own after your getting started book.

Giveaway Rules:

To enter, go back through this blogs archives and leave a comment below with a link to your favorite project or blog post you can find.
Make sure to make your comment using some sort of name (not just anonymous) such that I can announce the winner on January 16th when I do a random drawing.
Mention this giveaway on your Twitter, Google Plus, Facebook, etc. The more comments I get below, the more likely I am to bother continuing to give these things away, and there's better things to come.
For this first one, lets open it up to everyone; I'll ship this action international.

Come back on January 16th and I'll post the winner, who should then email me a shipping address to get this rather useful book to add to their collection.

Shooting at the Yolo Sportsmen's Association

2012-01-06T14:00:00.000-08:00

As my last celebration of winter break before school starts up again Monday, I figured I would finally get around to driving out to the local trap range and treat myself to an afternoon of shooting. It turned out to be surprisingly pleasant of an experience, and I had quite a bit of fun. The staff was very friendly every time I interacted with them, and when I went out to the trap range, there was two guys who let me join in for hot seat shooting, so we traded off every five shots, which was a lot of fun.

The Yolo Sportsmen's Association is, in good Yolo county form, out in the middle of nowhere. Off of 113, take county road 29 five miles West, and it's on the left.

Of course, Aviation Ave lacks a road sign, but the airport next to the range is well marked, so just follow the signs for it (or the YSA sign right above it to the right in the picture; see if I care).

The trap range had one thing new to me, which was a set of microphones, so I was able to go shooting by myself by just shouting "pull" into the five microphones and the machine would launch clays for me automatically. You did need to be a little careful reloading because the microphones would often pick up action noise and launch clays when you closed your action if you did it too loudly.

The price was decent. $3 + $6 per string, so when I first showed up I bought four tokens in the club house for $24, and then was able to drop the tokens in the trap machine to add 27 clay credits each (they give you two spare clays for misfires). They don't allow using your magazine, so you can only have one shell in your gun at a time, but they did let me show up and shoot by myself, which was nice because many ranges require you to be there with a friend.

This was the first time I've gotten a chance to shoot my Browning A-5 Light-12, having previously only shot my Winchester 1897, both in 12 gauge. I did alright; I managed to shoot about 22/25 on the '97 and 17/25 on the Browning. One of the other shooters was kind enough to come over and explain that the Browning shoots about 18" higher than most guns, so you need to aim low, which is what threw me off. As usual, they gave me some friendly flack for having the audacity to shoot guns older than they were (My '97 was built in 1935, the A-5 in 1955). Of course, it's my luck that I managed to slice my finger open on my '97 knuckle buster on the first shot, and never did manage to get it to stop bleeding before I got home. Next time, I'm bringing band-aids because of that gun.

The YSA also has 25, 50, and 100 yard pistol and rifle ranges, and an archery range, so they can facilitate pretty much anything you want to shoot.

Overall, the staff was refreshingly friendly, and I'd recommend them for anyone in the Yolo area who wants to go to a formal range to go shooting.

Tutorial on Using a Drill Press

2011-12-26T17:00:00.000-08:00

I'm quickly running out of both wood working tools and winter break, so enjoy these while they last, and I'll be back to my more typical hobbies once school starts again in January.

Video:

Using a Radi Plane to Cut Curved Edges

2011-12-24T07:00:00.000-08:00

The Radi Plane is a clever little hand tool for cutting simple curved edges on your work piece. This could also be done with a router, but when you're working on small projects where you only need to do a couple edges, this is much faster and easier.

Video:

Typically, you would be using better quality wood than I am ($2 2x4s), so you wouldn't be hitting knots and having as much trouble as I am in the video.

Tutorial on Cutting With a Scroll Saw

2011-12-23T07:00:00.000-08:00

After showing you how to use the band saw yesterday, I figured it would be a good follow on to show you how to use the scroll saw, which is the smaller cousin of the band saw. The scroll saw is meant for much lighter cutting, but has the advantage of being able to cut incredibly sharp corners, so you can do all kinds of detailing (or scrollwork, which makes sense...).

Video:

In the video, I also show you a basic project I did even when I was little, which was cutting out jig saw puzzles. All you do is take a thin piece of 1/4" wood and cut it into interlocking pieces, and bam; jig saw puzzle. Hours of fun.

Once you've done this and are looking for more involved inspiration, I was tipped off to one user on YouTube who uploads some interesting videos of him doing more some impressive work.

Tutorial on Cutting With a Band Saw

2011-12-22T07:00:00.000-08:00

Another quick little skill-building video tutorial today; this one is on the basics of cutting with a band saw. I know that most of my readership is more interested in my electronics, and those projects will return when I get back in Davis in January, so just hang tight and enjoy this month off while I spend some quality time with my dad's wood shop.

Video:

It has become easier and easier to get access to this type of equipment through hacker spaces and facilities like the Tech Shop, but if you are looking to put together your own serious wood shop, we wasted a lot of time and money before we finally bought all DeWalt tools. Ours is 20 years old, but I expect little less from the current model.

I've already gotten some comments asking for information on how to actually change the blade in the saw, so enjoy a bonus second tutorial just about how to change the blades.

Video:

The band saw tracking I mentioned in this second video works on the principle of a crowned pulley. Woodgears has a good introduction to crowned pulleys, as does Make Magazine in issue 22 pp 158-160.

Finally, here is a close-up of the band saw and guide blocks themselves. The blade will ideally not be touching any of the three of them (so if it is, adjust the guides and/or the blade's tracking), but inevitably will touch them as you feed stock into the saw.

Tutorial on Sweating Copper Joints

2011-12-21T07:00:00.000-08:00

Yesterday I showed you how to cut copper tubing using a tubing cutter. Once you have your tubing cut to length, you're going to need to somehow connect it to the fittings how you want. The traditional way to do this is by sweating the joint, which is the plumbing term for soldering.

The tools you'll need are:

A propane torch. If you're only doing small joints for crafts you might be able to get away with smaller crafting torches, but if you're trying to joint long lengths of tubing, appreciate that all that copper acts like a heat sink while you're trying to sweat the joint.
A flint sparker or other torch-lighting mechanism, if your torch doesn't happen to have a self-ignition system.
Steel wool. This is used for cleaning up the surface of aged copper tubing and removing oxide to ensure a good joint.
Plumber's flux and brush. This is important, because without flux the solder will just roll off the copper and not suck into it like it needs to.

Video:

The one thing to note in the video is that I interchangeably call the joining alloy solder or lead. Technically it is 40% lead and 60% tin, so I misspoke in the video.

This is all explained in the video, but the steps to sweating a joint are:

Clean all surfaces to be joined with steel wool until shiny.
Apply flux to ensure good connection between the copper and solder.
Join the fittings and apply heat to the whole connection.
Touch solder to a single point on the joint, and enjoy seeing it magically suck in to make a solid joint.

Be careful while applying solder that you don't apply too little solder, but once you apply enough, the excess will drip from the bottom of the joint. Try not to burn yourself.

This is the finished joint. Notice how the solder readily sticks to the surface of the copper. If your solder just beads up and runs off, you need to clean the surface again and apply more flux.

Since I'm using this for crafting and not actual serious plumbing, I also take the time to hit the joint with a wire wheel to clean off the excess burnt flux once I finish. It cleans off very easily.

Tutorial on Cutting Copper Tubing

2011-12-20T07:00:00.000-08:00

Being able to cut copper tubing can be useful around the house, but I also find the various sizes of copper tubing to be useful crafting supplies, so while I don't tend to do much work putting together gas lines, I still do this quite a bit.

Video:

The process is rather straightforward. Using a tubing/conduit cutter, place the tubing between the cutting blade and the two rollers and tighten the cutter until the blade is just touching the tubing. Then simply spin the cutter around the tubing, tighten the cutter approximately an eighth to a quarter of a turn, and spin it again. Eventually you will cut all the way through the tubing and it will separate. Once you finish cutting the tubing, use the deburring triangle on the back of the tool to smooth the newly cut openings.

Toy Waterworks Project

2011-12-18T18:00:00.000-08:00

To continue the series of toys from my childhood, this was one of our summertime favorites.

The concept is quite simple; given an adapter from a standard garden hose to 3/4" slip fit PVC pipe and an assortment of pipe fittings and lengths, you build your own water park in your back yard. PVC also comes in threaded sections and fittings, but as small children, it was much easier to assemble and disassemble sections when they were just press fit, and half the fun was trying to keep all the sections stuck together as you built higher and higher towers. We spent hours putting together and taking apart these pipes and generally just making a wet mess of ourselves.

The only part that you need which is a little unusual is the hose-to-3/4" slip fitting, which you will rarely find as one piece. What you can find is female slip fitting to male hose thread, and female-to-female hose thread fittings. This set is pretty free-form, so you can grow it or shrink it as much as you and your children feel inclined. The prices I quote are from Orchard Supply Hardware, but most hardware stores will have these parts in their plumbing section.

3/4" slip to male hose thread - $1.89
Female-to-female hose thread - $2.89
27' (3x9') of 3/4" schedule 40 PVC pipe cut into 2-4 foot lengths - $5.97

You can also buy pre-cut sections if you don't have a pipe cutter, but they will be more expensive and a pipe cutter is something you'll find useful.

3x plastic flushhead sprinkler heads and risers - $2.94
Reducing tees and/or reducing ells from 3/4" to 1/2" NPT to screw sprinklers into - $2.07
12-15 assorted tees, ells, caps, three-ways in 3/4" slip fitting to connect the pieces of pipe - $5
A hot summer day - priceless.

In case you have never cut PVC before, it is very simple if you have the right tool. Video:

Unfortunately, I can't find any pictures of us playing with ours when we were little, and it is much too cold for me to go outside and stage a dramatic reenactment, but hopefully you get the idea.

I would suggest you buy the bulk 10' sections, but it is possible to buy pre-cut shorter pieces.

These reducing fittings are to screw into the risers which connect to the sprinkler heads. You can have fun with just the reducing fittings themselves as a bubbler; the pipes won't tend to stay together if you have all the ends capped in sprinklers.

This is shown with a brass sprinkler head, but you'll find the much cheaper plastic heads in the same place.

Numitron Display Tube Tutorial

2011-12-08T22:00:00.000-08:00

Anyone following my electronics projects from the beginning has probably already picked up on my love of vintage displays. I've done several projects with old vacuum fluorescent displays and nixie tubes, but Christmas came early for me today in the post.

I just got a package from Russia today with half a dozen IV-9 numitron tubes in it, which are a different display tube from the same era. How numitron tubes work is that it has eight tiny incandescent filaments arranged in the typical seven-segment plus decimal point configuration, and you simply pass current through the filaments you want lit up, and they literally light up exactly like a light bulb. They are still pretty easy to get online; you can get the IV-9 tubes I'm using for less than $3 a piece on eBay.

Video:

This filament display has a huge advantage over VFDs or nixie tubes. VFDs take 40-60V and has the complexity of a heated cathode; nixie tubes require a heart stopping >120V, and both types require rather specialized driver ICs because of these high voltages. Numitron tubes, on the other hand, only need 2-3V, so I was able to use jellybean constant-current linear LED drivers out of my junk box.

As a proof of concept, I plugged a numitron tube into a breadboard over an Allegro A6278 LED driver, but any constant-current driver will work, or even just some resistors and transistors. I hooked this up to an ATTiny2313 AVR and wrote a simple piece of code that cycled through all the digits 0-9.

Finding information on the IV-9 tubes is a little challenging if you don't happen to be able to read Russian, but about the only critical piece of information you need out of the datasheet is the filament current and the pinout, which are relatively easy to find; the filament current is still labeled mA, and the pinout diagram is relatively straight-forward once you realize the pins are numbered clockwise looking from the bottom of the tube. These filaments are specified for 17-22 mA.

Like always, now that I have the proof of concept running, I'm working on a larger project, so look forward to that in the future.

Two Phone Intercom Toy

2011-12-03T22:00:00.000-08:00

I like the idea of writing a series on the home-brew toys that I grew up on (and actually still play with some now). My childhood was one filled with days of playing with packing material and old electronics rubbish that comes from growing up as the child of a chemist turned EE in the Silicon Valley.

One of these toys that I played with was a rudimentary intercom, build from a pair of analog telephones, a 9V battery, and a single resistor (and optionally some LEDs). My pictures and videos show the battery and resistor loose and just clipped on, but it would be very easy to build a more robust toy with a standard plastic gang box and a dual phone jack module from ACE or Home Depot.

Video:

The intercom lacks most features; it can only handle two phones (or more, but all must be off-hook and in series) and unless you can find some real pulse-dial phones, you can't even ring the other phone (If you're lucky, pulse dialing will in fact ring the other phone). Even still, it is a very impressive version of the classic two cans and a piece of string toy. Run the cables between children's bedrooms, or up a tree house, or anything else you can come up with.

The principle of operation is very simple. Phones operate over a single pair of wires, which carry both sides of a conversation at once. The microphones rely on a bias-current flowing through them to pick up sound, which is why you can't just plug two phones together and hear each other. By splicing in a 9V battery and a 300 ohm resistor, you can crudely insert 5mA of current, which is enough to at least hear each other. Conveniently, when either phone is hung up, they go into a much higher DC resistance state, meaning that this loop current being drawn from the 9V battery is stopped when it's not in use.

As shown in the video, if you also put an LED in-line with the phones, it will light up when both phones are picked up. An obvious extension to this system would be to install an LED in both phones, so that the users can tell when the other phone is picked up.

Of course, in this day and age. if you wanted to put together a more sophisticated system, with multiple phones, ring service with extension numbers, spanning more than your house, etc, it would be entirely possible. On eBay you can get several Polycom or Grandstream SIP VoIP phones for less than $100, then plug them into the internet anywhere and your kids can call their friends as much as they like. I've shown how to do this in the past.

Two Player Chinese Checkers Board

2011-12-02T22:00:00.000-08:00

For anyone who doesn't happen to have a subscription to Make Magazine, let me say that their latest issue (#28) is quite good. The theme is "Toys and Games," and after reading through it there are more than one projects I think I'm going to do something with.

The first such project which I have gotten a chance to build is the two-person Chinese Checkers board. Traditional Chinese Checkers is a six-person board, but that comes with a short-fall; four or six people playing and strategy is usurped by chaos; two players playing and the wide expanse of board allows much confrontation to be avoided. On pages 56-57, Charles Platt gives plans for this two-player configuration [PDF warning]. I liked the look of his board in black ABS, so while I was in Sacramento for the FE exam, I stopped by my nearest TAP Plastic and picked up a piece of 8"x16.75" single-side textured ABS. I think the cost of it came to something like $12.

Of course, in the article, he explains how to drill the hexagonal matrix of holes by hand using a drill press, but trying to drill 61 holes by hand and get them to all line up just right seems like a tedious task to me. Luckily, since I am a mechanical engineer at a world-class university (and paying quite a bit more than expected for the pleasure), I figured I would utilize the facilities provided to me for such personal projects.

As a student of the mechanical and aerospace engineering department at UC Davis, I am allowed access to the Engineering Fabrication Laboratory, which gives me access to 6 CNC end mills, plus as many lathes, and various other useful equipment such as drill presses, fully equipped welding bays, a sheet metal brake, wire EDM, the list goes on.

It was these CNC mills of interest here. They're outfitted with MillPWR CNC controllers, which means that you can program drill patterns quite easily through the attached control panel (and save said patterns to floppy disk). I figured out what the file format is for the hole patterns, and then wrote the code needed for the tedious task of these 61 holes.

Now drilling the entire board is simply a matter of telling the mill exactly where the bottom left corner of the ABS plastic is, and then successively telling it to move to the next hole position and manually drilling the hole. You can automate the entire drilling process, but it is often faster to control the drill speed manually than to have the mill operate on its own.

Look forward for other projects from this issue, or shout out in the comments if you've done anything from it yet as well. I'll hopefully have some more time for such next quarter. If you don't yet have a subscription to Make, I'd highly urge you to; it may be only a quarterly issue, but they are always of high quality.

Appendix A: MillPWR code

My First Model Railroad Ops Session

2011-11-14T20:00:00.000-08:00

School and life have been pretty crazy as of late, in case anyone hasn't noticed the precipitous drop in post frequency already. My roommate decided to offer me a break from my school work this weekend and invited me to her dad's ops session on his HO model railroad layout. Of course, I'm a big train fan (being active in both the WPRM and WRM museums), but modeling hasn't appealed to me in a long time, since it's pretty hard to beat 12 inches to the foot in detail or realism. I didn't really know what to expect, but boy was I impressed.

First lets talk about Phil's layout. The women of his family were kind enough to allow him to go off and build his own man cave, separate from their house; talk about living every man's dream. This second picture shows about a quarter of the envisioned layout, and something like 90% of what's built so far. He's targeting 1950' era Union Pacific branch line, which is about ten years early for me (much too many steam engines still running around for my taste, but he did have two token EMD and Fairbanks-Morse diesel switchers in the yards).

The entire layout is DCC controlled, which is an incredibly elegant system which uses modulated AC in the tracks and then individual microcontrollers in each locomotive decoding these command signals. This means the entire layout can be wired as one electrical block, instead of the traditional system where you electrically isolate every chunk of track that you want to operate on independently using DC. Each of the operators then have their own throttle keyed to the ID number of their locomotive, so as they issue speed commands, the commands are sent to all the locomotives, but only followed by the one matching the programmed road number. Add in that the throttles are wireless (915MHz ISM), and it means that you can drive from one end of the layout to the other, while walking around with your train, without having to worry about other operators, beyond them not physically being in your way.

The layout being DCC became important once you put ten guys in the room, because some of the rail yards started getting pretty crazy with two or three operators working them at once.

I have done plenty of hours of actual yard switching, but I had never been to a model ops session before, so what came next I certainly didn't expect. It turns out there there is a dispatcher in an adjoining room, but in the 1950's wireless radios weren't particularly useful, so Phil actually has hard-line telephone handsets under every station that you can pick up and talk to the dispatcher on (a few of the handsets can be seen in the second picture above).

Furthermore, Phil had timetables printed up for the "scheduled" trains on his layout, following wall clocks running at 4x real time speed.

This meant that as an operator, I was handed a throttle and assigned a locomotive, and keyed the locomotive road number into the throttle to take control of it. I then answered the ringing telephone under the table and spoke with the dispatcher in the other room, who assigned me to train #22, gave me special instructions for the run (a slow order by the Weber Branch), and authorized me to take the main line following the prescribed timetable. Once I reached Wanship, I knew that I was going to meet the Westward #21 so I went into the hole and waited the 20 minutes (5 minutes real time) before being passed by it. I then continued onward to my final destination of Park City. Of course, this was all complicated by the local switching and extra trains scattered throughout the layout by the dispatcher to keep things interesting, but being a scheduled train meant I didn't need to worry about much more than one flagman who had fallen asleep on the track.

Overall, it was a very fun way to spend a Friday night. It's going to be one impressive layout when it's completely done; I'd say it'll be able to easily accommodate a good 25 operators simultaneously. If you have any further questions about the layout itself, I'd venture Phil probably wouldn't mind if you contacted him at Gulley [at] pasco [dot] com.

I Got Interviewed for EEWeb

2011-10-31T12:00:00.000-07:00

Hey everyone. Things have been a little crazy as of late with midterms, and I just took the FE exam this weekend (which was much overrated), so there isn't much in the pipeline other than more SerialCouple testing and maybe some initial work for my senior project. To keep you entertained in the mean time, EEWeb contacted me this summer and did an interview asking about how I got inspired to be an engineer. It's an interesting read, so I encourage you to go check it out.

SerialCouple Used as Sous-Vide Controller

2011-10-25T23:00:00.000-07:00

The testing of the SerialCouple prototypes continue (Part 1, part 2, part 3). For those not following along, the SerialCouple board is a low cost thermocouple adapter, meant to be used in conjunction with a standard FTDI USB adapter to enable you to monitor and log a single thermocouple channel to a computer using standard serial port monitoring software. Production boards are still a few months out, but while they're in the works, I've been playing around with different things to do with the SerialCouple. This demonstration is taking advantage of the extra IO pins afforded on the serial port connector to control a heater as a sous-vide cooker.

Sous-vide is a hip cooking method where you vacuum seal the food and then cook it long and slow in an elevated temperature water bath. The challenge is that you need fairly precise control of the water temperature for food safety and cooking quality reasons. By cooking food in this long and slow manner, it is possible to bring the food to a single consistent temperature throughout, which enables you to have a perfectly medium-rare steak ALL the way through the meat, or a soft boiled egg that is perfectly soft ALL the way through.

How I built my sous-vide cooker is by attaching one of my SerialCouple prototypes to a junction box which I built with a solid state relay in it. This SSR is then used to control a 615W lab hotplate, which heats the pot of water which I'm monitoring with the SerialCouple. The SerialCouple handles all of the thermostat logic internally, with the SSR connected to the CTS pin of the serial port connector. With the addition of a >4V battery, this can operate entirely independently of a computer (after using the computer to set the target temperature).

I used a 9V battery clip and a 6x0.1" female header to make the adapter cable, although only the bottom three pins are used, so a smaller socket could have been used.

I had to blue-wire jumper the CTS and RTS lines on my prototypes, since I only bothered routing the transmit and receive on the PCB itself. In the next batch, I'm going to route all six pins, as well as correct all of the other routing mistakes I've made.

Water Temperature Performance

I played with implementing a PID algorithm on the SerialCouple a little bit, but I eventually came to the conclusion that the simplicity of a basic thermostat (heater on if below set point) algorithm, coupled with a correctly sized heater, have adequate performance for my needs. In the initial trials, I only used 2 cups of water in the pot to see how well the SerialCouple could maintain a set temperature. Unfortunately, the hot plate was powerful enough that the transfer delay between the hot plate and the pot caused the system to oscillate, but turning down the power, and later adding more water, significantly improved performance.

The first trial was with various power settings on the hot plate to a set point of 50C for 2 cups of water. As can be seen in the graph, this tended to oscillate a couple degrees, but not as much at lower power settings. These graphs were made by tapping the serial connector with a USB adapter and logging the output to a file with PuTTY, then graphing them in MATlab.

The next trial was with 6 cups of water at a temperature set point of 64C. This was to test soft boiled eggs, which you need to cook for at least 45 minutes. Since you're cooking eggs (which you can just leave in the shell) in a low temperature bath, the proteins won't over-cook and become unappealing, because they never get hot enough to. The power settings for this trial was 4/6, like the red line in the previous graph, except for the middle third of the heating up ramp, where I got impatient and turned the hot plate full power (which you can see in the graph as the change in slope on the way up).

Zooming in on the set point when the water bath reached it, it can be seen that there is minimal oscillation, considering the ADC's resolution. I'm happy with this level of stability, considering that it's monitoring an unagitated water bath (which tends to have a few quarters of a degree of noise just due to turbulence). You can clearly see the quarter degree limit in the ADC's resolution in the graph, which is what causes the jaggedness of the lines as it jumps between possible readings.

So how did my overly-complicated soft-boiled eggs turn out? Amaaaazing! I just had to crack off a nickle-sized piece of shell, and was able to pour then entire egg out onto a piece of toast. The yoke was tacky firm, and all of the whites were a consistent creamy consistency; almost a runny pudding or a custard consistency. If you're a fan of soft-boiled or over-easy eggs, I highly suggest you try cooking them like this. It is quite outstanding.

As I said, work is progressing slowly on revising the SerialCouple boards for production. I'm planning on fixing all of the routing errors, and adding the option of a PCB thermocouple jack instead of the screw terminals I'm currently using. Current expected cost is going to be about $30 (plus an FTDI cable if you don't have one already). Email me if you're interested in possibly buying one when they become available (sometime around January 2012, I expect) and would like to be kept updated.

Monitoring an Oven with the SerialCouple

2011-09-26T17:00:00.000-07:00

Progress on the SerialCouple boards has been coming along. I think I've identified all of the hardware issues, so now it's just a software problem. I decided to have some fun with the prototype today and have it monitor my oven while I baked a batch of brownies. The SerialCouple boards are rated for the entire K type temperature range (-200C to 1350C), so the only limiting factor as to how hot you can measure is the rating of your thermocouple.

My new roommate happened to walk in on me setting all of this up. That was a rather amusing conversation... Luckily, she's learning pretty quickly to tolerate my eccentric hobbies, which I appreciate.

I had a little difficulty installing the thermocouple, because some parts of my oven door are grounded, which causes the ADC to issue a fault code, but using a non-metallic sheathed thermocouple, or in my case finding a non-grounded section of the door fixed that.

I generated the graph by having PuTTY log the serial port to a file, then imported it into MATlab and plotted it to a png. Pretty simple, but I have visions of eventually writing a proper DAQ interface for the SerialCouple, likely in Java.

Looking at the graph, you can see that I added the brownies at the 8 minute mark, checked on them at the 35 minute mark (2100 seconds), and declared them finished and turned off the oven at 38 minutes. The oven temperature was set to 325F, so it does seem to run a little hot. When baking, I would typically let the oven pre-soak a little more before adding the brownies, but I was in a rush for some baked chocolate deliciousness today.

Volunteering in Rio Vista

2011-09-24T20:00:00.000-07:00

The Western Railway Museum (not to be confused with the Western Pacific Railroad Museum which I also volunteer at) has track work weekends twice a month, where we go out and do maintenance work on the several miles of track that the museum has in service. A typical Saturday consists of driving a few miles down the line and replacing every other tie under the track (which I have written about previously) or straighten and repair rail joints. This was certainly not a typical weekend.

The old Sacramento Northern line that the museum runs on has a number of trestles originally built in 1939, which inevitably need to be maintained. The project this weekend was to replace the center bent, which has been suffering from being in standing water, so we were to replace it with a shorter bent, and pour a new concrete cap on top of the old foundation to keep the wood from sitting in the water that collects underneath the bridge. Joel had already staged the new bent to the left of the old one, the concrete frame and forms on a flat car on the bridge, and jacked up the bridge.

First thing to do was to cut out the old bent. This was done with a sawzall powered from a diesel generator, while the top cap was held in place by the tie crane on the bridge.

Once the legs were cut out, we lowered the top cap to the ground.

We found a few of the original 1939 date nails in the lumber we were tearing out, so we pounded them into the new bent, for "historical accuracy." It hurt the engineer in me a little to improperly date-mark the timbers, but I've already got a 39 nail from the last time we replaced ties, so it seemed like the best thing to do with them. They were in surprisingly good condition for 72 year old nails.

Some of the nuts were so rusted onto the bolts in the old bent, it was twisting the wrought iron bolts that finally broke, not the stuck nuts.

Once we had the old bent out, we cleaned up the old foundation.

We then took the new concrete cage and lifted it into position.

Getting a concrete contractor to come out on a Saturday was going to be an ordeal, so we only framed it all up such that we could have someone come in Monday to pour it for us.

We then used the crane to lift the new bent into position, and bolted it to the 16" stringers to hold it in place until the concrete can be poured.

Once the bent was bolted in place, we took a break for lunch, and then installed the concrete form for the new foundation cap.

Everything went extremely well, which is mostly thanks to all the hard work Joel put in beforehand staging everything. Since the new bent is a foot and a half higher, hopefully the new lumber won't sit in water and rot out like the old one.

It was a fun day. I keep trying to get down to Rio Vista more often, since they work every second and forth Saturday, but college keeps getting in the way. Hopefully I'll have more time this year to work there. If anyone in the Sacramento area would like to get involved, email me and I can put you in touch with Joel, who is in charge of the track crew work weekends.

MAX6818-Based Debounced Breadboard Keypad

2011-09-21T18:00:00.000-07:00

This was a quick little project I put together while I was bored this week. This is an eight button keypad, but uses the Maxim MAX6818 part to debounce all of the buttons. This is important because when you connect regular buttons to TTL logic or a microcontroller, you don't realize it, but every time you press it, the button will bounce on it's contact, often several times, causing more than the single desired edge.

This is usually solved by implementing some sort of low-pass filter, to convert the multiple fast edges into a single, slightly slower edge. This can be done in software, or even just using a simple RC filter with a Schmitt trigger to clean up the slow rise time. That being said, it's always a pain for every project to have to wire up a bunch of capacitors and resistors, or copy-paste in the exact debounce software every time I want a button, so I designed this button module which can plug into a breadboard and have eight debounced buttons right away.

The MAX6818 is quite nice, in that it implements a 40ms low-pass filter on eight button inputs, has internal pull-up resistors, has an open-collector pin-change interrupt, and even tri-state outputs so you can share the buttons with other devices on an 8-bit bus. I brought everything out to a 0.1" edge connector, which when populated with male header can plug straight into a breadboard. I also added a solder jumper, such that you can hard-wire enable the outputs if you aren't interested in tri-state capabilities.

Unfortunately, I didn't bother checking component costs until after I finished the design. The Maxim debouncer chip is more than $8! Considering this can be implemented with a 50 cent 74HC14 chip, this thing really is just a waste of money, unless you're only planning on using it yourself, in which case you can sample the part from Maxim.

So, I'm not going to bother having this fabricated, but I will release the design files CC BY-SA, so if anyone else wants to actually order these and test it, do with the files as you will.

Design Files.

If you do order them from someplace like Dorkbot or ITead and end up with spares, I would be interested in buying one or two of the copies off you, just to have something to do with my MAX6818 samples.

SerialCouple V1 Demo

2011-09-17T11:00:00.000-07:00

I've written about this project a little before, but I figured I would give an overview of it's capabilities all in one place. The SerialCouple line of boards are simple, easy to use single-channel thermocouple adapters, meant to be an interface between a thermocouple and a computer or other embedded system. Shown in the pictures are the model one boards, which are meant to be plugged into FTDI-like USB-to-Serial adapters, but a second model based on RS-232 is in the works.

I've been doing all of my testing with the most standard K type thermocouple, but the MAX31855 part I'm using also supports J, N, T, E, S, and R junctions, which differ in their rated accuracies and temperature ranges. K thermocouples are rated for measuring temperatures between -200C and 1350C, so for most hobbyist projects, they're perfectly sufficient. With thermocouples, you can typically expect precision on the order of 2C or 0.75%, and the SerialCouple board supports 2 bits of resolution below the decimal point (so temperatures are read in steps of a quarter degree). If you're interested in higher resolution than that, I'd suggest you take a look at my analog K thermocouple amplifier, which must be connected to your own ADC, but can give much higher resolution readings.

Video.

Here is a closeup of the board populated with an Omega MPJ thermocouple jack. I did make one routing error on the boards, which can be seen by the blue wire between the ATTiny2313 and the MAX31855. This is the one downside of AVR ICSP being on the SPI bus, in that if any other SPI device doesn't want to stay in reset during programming, they'll keep you from being able to reflash the AVR. (Fun side note: I didn't solder most of this board. It was done by one of my friends as his first time doing surface mount.)

The design was done in Eagle, and I am working on making everything for it available on a Google Code page.

I have been having some problems with my USB adapter. The ADC works fine, except when I'm receiving anything from the USB adapters. Initializing the adapter (an MCP2200 in my case) adds a very high frequency broadband 200mV P-P noise on the 5V rail to the SerialCouple board, which manages to get through the regulator and by-pass caps, and causes the ADC to read 3-10 degrees low.

I've solved the incorrect readings issue. Maxim's claim that the MAX31855 chips require no input filtering is incorrect; two 10nF caps resolved all of the noise issues for the model one boards.

There has been some interest in people buying the board, so once I get some more bugs worked out and spin another revision, I'll be open to the possibility of selling the blank PCBs and possibly completed boards. Sound off in the comments with any interest or questions.

FastPort Model 3100CXPlus

2011-09-15T20:00:00.000-07:00

After trying out the 86BT in my parent's house as their network printer solution, we were a little underwhelmed with the build quality of it. The BT86 is certainly functional, but its build quality is pretty unimpressive and didn't instill much confidence in the parents. All the well, because it means I get to keep playing with it, but it means I still needed to find an Ethernet solution for the parallel port printer.

I managed to get a good deal on this beautiful piece of work, a FastPort Model 3100CXPlus. This thing is built like a tank, and taking numbers. The case is made from heavy extruded aluminum, and is about the most solid thing piece of electronics I've ever played with. It was originally made for corporate networks back in the late 90s. This specific device has a firmware build date from 1997, so it's OLD, but still working.

It's a very simple device; an Ethernet jack to plug into your network (10bT, amusingly enough), then a DB-9 serial port and a DE-25 parallel port to plug printers into. What is a little squirrely about it is that it has two DIP switches on the front to switch it between a couple modes, and of course the user guide for it off-handedly mentions that specific switch settings can be referenced from the installation manual, which is nowhere to be found online. It then exposes these two printer ports as TCP sockets, which can be set up as RAW TCP/IP printers on any operating system.

Turning on D1 sets the device into configuration mode, where D2 then switches between printing a test page (D2 off) and setting the device into serial configuration mode (D2 on).

So, for example, setting the switches to on and on, and then plugging a null serial cable into the serial port to your computer, and opening a hyperterminal at 9600 baud brings up a menu system to configure the device.

Setting D2 to off and power cycling the device causes it to try and print a test page on any printers plugged into it (using what looks like basic PostScript, but having never looked at PS before I am only guessing). Of course, our Laserjet 2300 is a PCL printer, so the test page mode did nothing.

To then set the device into standard print mode, turn off D1 and turn on D2. I never figured out what off-off did. In addition to exposing the two printers on ports 2000 and 2001, you can connect to it through telnet on 2002, and either monitor status or remotely configure it exactly as done through the serial port in configuration mode.

So of course, while I was playing with this, I had to open it up and check out some good 1997 circuit board action.

There were a few things distinctive about this board. First of all, it's the first PCB I've ever seen designed to slide straight into an Aluminum extrusion case. Second of all, it actually has two banked EEPROMs for the firmware, which are the two PLCC ROMs at top center. This means flashing new firmware actually requires booting off one bank, flashing the second, then rebooting off the second bank to flash the first. Talk about a robust system! You'd have to really work at it to brick this thing.

Third feature of note is the 16 pin edge connector inside for a daughter network card, which can replace the blank-off cap seen to the right of the Ethernet jack in the second picture from the top. This allows you to buy additional network cards to allow this thing to support any of the dizzying array of network solutions eventually beat out by twisted pair Ethernet, including coax Ethernet, token ring, and AppleTalk. Again, impressive.

On top of everything else amusing about this thing, the microcontroller running the show easily takes the cake. This thing runs on a freakin 80C186, which was one of the stepping stones between the classic Intel 8086, and the 80386, which defined the entire PC revolution. Not only is this a classic controller, but back in the 90s it was common practice to license your ICs to other companies as "second sources" such that manufactures would be willing to use your part (since they can buy it from either you or your licensee). The 80C186 was developed by Intel, but this one happened to have been manufactured by AMD, which can be seen by the (M) AMD (C) INTEL silkscreen, which is quite rare now.

So, all being said, this is an amazing device if you still happen to be using a parallel port printer that you want to put on the network. The 10bT Ethernet isn't much of a limitation, since parallel ports are slower than that anyways, and it handled multiple computers simultaneously trying to print to it no problem. If you happen upon one of these things at any kind of salvage shop, or on eBay selling for a lot less than the $100 they seem to be going for these days, grab it.