By now you may be asking yourself: How can I keep up the the antics of a 28 year old computer terminal?

Well, the wait is over!

Last night I was playing around a bit with the host software. The host is a current PC which listens for data from the terminal. It then assembles the text sent from the terminal and does something with it. In this case, it Tweets. In other words, the PC is an internet gateway for the terminal, acting very much like a mainframe or other host would.

Long story short, I can type up junk on the Terminal, hit enter twice, and a Tweet gets posted.

HP 2382A Terminal Twittering With My Homemade XBee Modem

You can follow these exciting adventures by searching for “HP2382A” on Twitter, or follow the feed here (you need a Twitter account): HP 2382A On Twitter

Now this may sound sort of silly, and it is in a way, but it’s a great way to experiment with a couple of technologies at once: Xbees running ZigBee wireless, wireless RS-232 communications, networking old equipment, writing host software, learning the Twitter API, and so on. It will now be easier for me to mess with other (more prosaic) uses of the XBee, like remote sensor monitoring and the like.

What do you with an old cracked Dell laptop screen? Make an LED effects project, of course!

Check out Evelyn’s write-up on here blog, here: Northern Lights Project, Part 1

This was a really fun project for us. Not only did it teach us stuff about how LCD panels are made (amazing how much they put in a simple display), but it also taught us how to cram a lot of stuff in a small space.

In addition, Evelyn used a 6276 LED Driver. It’s a cool way of running a lot of LEDs, since you need only a handful (<6) data lines to drive 16 LEDs. Plus, they can be daisy-chained, so you can drive a ton of LEDs with just a half-dozen data lines. Neat stuff.

Northern Lights With Broken LCD Screen And 6276 LED Controller

You’ll notice that in her photos she is using the modem enclosure seen below. We just decided to swap it out these evening. In it’s place we’ll be using a shiny “Design By Porche” hard drive enclosure (the hard drive controller died, so now we have a nice case).

Take a look at the videos once she has them up. The display is really neat and Evelyn did a great job making the project look very polished and professional.

Not one to be happy with the mess of cables and development boards sitting on my nice antique HP terminal, I decided to make my own (short) RS-232 cable, and then put everything in a nice enclosure.

I was able to scavenge a 25 pin male connector from an old PC’s ‘daughterboard’ and wired it up with its ribbon cable and another spare 9 pin male connector. The end result was a nice short (8 inch) cable that is perfect for attaching a 9-pin modem to the 25-pin HP connection. Worked better than the store bought ones!

Next up, I needed a case. We were going to repurpose an old metal case for one of Evelyn’s projects, but ended up doing a swap-a-roo. Here’s what I ended up using:

XBee Modem For HP2382A (Or Anything Else)

A Zigbee wireless modem stuffed inside an old 2400 baud modem enclosure. That’s what you call technical irony.  

Here’s the rear view:

The antenna is on the left (I opted for the bigger antenna for this project, since I wanted range, but they have MUCH smaller ones available–the size of a matchstick, and smaller). Next is the reset button (lucky chance it’s visible there). Then status LEDs, the RS-232 with home-made cable, more status LEDs (signal strength), and finally power.

The XBee development board fits quite nicely in the little modem case (about 6 inches by 4.5 inches–it’s not a huge one). I opted to keep the Xbee (which is only the size of a matchbook) on the development board. I have plenty of them, they have a power supply on board, the connectors, and the reset. Wasn’t worth wiring my own.

So now I have a handy little Zigbee/Xbee test modem for whatever project I want to mess with, all nicely packaged in a strong enclosure.

Next up, writing software on the PC which will present something interesting on the “dumb” terminal.

As I mentioned in my previous post, I have an old HP 2382A terminal on hand. I picked it up ages ago, but never really quite had a use for it. Part of the problem was that you either have to connect it to a regular modem or direct connect through an RS-232 cable and a null modem. What’s the point of having a terminal 12 feet from your regular PC?

Very often I’ve found that a new bit of technology becomes available which can help resurrect older stuff. Such is the case with the variety of wireless technologies available today which I didn’t have 7 years ago when I bought the HP. One of those is ZigBee standard. It’s a wireless standard like WiFi, except it’s more focused on mesh networking (for collecting sensor readings, for example).

Back in November of 2007 I had purchased a couple of the Xbee wireless modems from Digi. (Xbee is the brand name of ZigBee modules made by Digi.) I had played with them a bit, but no projects really came of it. Now, in May of 2009 I dug out my old HP terminal, and it needed a modem. Voila! I could connect a XBee to a Internet connected PC and another XBee to the “dumb” terminal. To the terminal it looks like any other old-school modem. Now, finally, not only would my 28 year old terminal be used, but it would have wireless network access!

HP 2382A Terminal With XBee Zigbee Wireless Modem

Keep in mind that this is a text display-only terminal. It does have a CPU and firmware, but only for display and communication purposes.  In other words, it won’t run programs. However, it does send and receive data, so you can have it send keystrokes to a remote computer, and the remote computer can send text back to display on it’s tiny 9″ white on black screen.

So, I can’t run a web browser on the machine, but I can run software on the host (a current PC) which can act as an interface between the Internet and it. For example, I could have the host PC display current news, maybe. It could even be a Twitter client (something I was thinking of, from a purely ironic standpoint).

It seems a bit silly to make an old terminal jump though hoops like this, when I could just sit at a normal PC. But that’s not the point. What’s interesting is taking a new bit of techology, the XBee, to enable a piece of equipment that has not been used for 25 years. At the very least, I can pretend that I’m in the movie Brazil.

I’ve recently been working on  a wacky repurposing of an old (circa 1981) HP 2382A terminal. This “dumb” terminal used to retail for around $1700 and is now next to useless. The trouble is that it works perfectly (take that, 2 year old iPod and 1 year old Sharp TV). I wanted to put use to it.

It used to connect to a modem, or was hardwired, via a 25 pin RS232 port. You rarely see those on PCs these days (even the 9 pin version is well on its way out). Lucky for me I have a large collection of old cables on hand, so I was able to experiment. After some trial and error, and the inclusion of a null modem, I was able to get it directly connected to my laptop.

The trouble is, when I tried another cable, it wouldn’t work. Then I noticed the difference: For the direct connect I had used a super-heavy 25 pin extension cable, then a 25 to 9 adapter at the laptop. With the alternate configuration I used a cable that had 25 pins on one side and 9 on the other (so that I could ditch the heavy cable and adapter). The problem was that the cheaper cable must not have had all the legacy data lines in place so it wouldn’t work. A stupid cable was causing a lot of heartache.

Lessons learned for others who might be connecting a legacy terminal to a PC:

• If you are doing direct connect between the terminal and the PC you must have a null modem in-line. The null modem switches the transmit/receive pins (among others).
• If you are using a modem (wired or wireless) between the terminal and the PC you do NOT need the null modem (since the modems are your modem). 
• If things are not working, check your cables. This is especially true with older equipment, which do use all of those “unused” wires, at least most of them.

More to come.

Evelyn is working the the SkillShare Austin people to possibly do a workshop on building the Digital TV Antenna. If this happens, we’re going to be putting together a kit of parts for the antenna. Would include the wood, hardware, hangers, and antenna transformer. The wood would be pre-marked and drilled, so you’d have to do is the coat hanger work and then assembly. If anyone is interested, let me know, and I’ll make it available to a larger group.

Just got back from an IMAX showing of the new Star Trek movie. All I have to say is, thank goodness for “reboots”. The technique saved Batman and it looks to save Star Trek. An enjoyable action movie even if you don’t like Trek. Some of the concepts of the ‘boot I’m not quite sold on, but if it helps the franchise, so be it.

Most of the over-the-ether TV stations in the US have switched over to digital transmissions. Evelyn has an old, but very reliable, Toshiba 13″ CRT that we purchased a convertor for.

Up to now, we have used simple “rabbit ears” for the TV. Since we aren’t too far from the transmitter towers, they worked pretty well, though garbled out once in a while. (In digital there is no static, there is a digital disaster if your signal is weak.) There were also some channels we simply could not get, but didn’t care enough to purchase an often expensive “digital” antenna.

Now digital TV is broadcast in UHF. Basically the band that used to be channels “14″ to “83″. UHF runs at a higher frequency than VHF (“2″ through “13″). What does a higher frequency mean from an antenna standpoint? A smaller antenna. For example, in Ham Radio, you might want an antenna several hundred feet long for very low frequencies. As you get to the higher frequencies a simple, very short (<8 inch) antenna is all that is needed.

THERE IS NOTHING DIGITAL ABOUT AN ANTENNA. For an antenna to work it has to be tuned to the frequency you want to receive. If the signal is broadcast of 440 Mhz, you need an antenna that is designed for that frequency–it does not matter one bit if the transmission is analog or digital. The length of the antenna elements is what counts.

Before I get too involved in antenna design, let’s get back to the Best Digital TV Antenna out there. It’s so special that you can’t even purchase one in a store!

Here’s a photo:

Evelyn's Digital TV Antenna

Doesn’t that look like some wires attached to a 2×4? Right you are! Those are 6 coat hangers cut, bent, and mounted to a 2×4. Or, as we call it, Evelyn’s Afternoon Project.

What you see are a 20″ piece of 2×4, some screws and washers, 6 wire coat hangers (free from the local thrift shop), a piece of old twin-lead antenna lead (regular wire is okay, if kept short), and a reclaimed 300 ohm to 75 ohm antenna transformer (we added a coupler, since we didn’t have the right one on hand).

Here is a photo of me zip-tying the transformer to the board:

Ron Working With Coat Hanger Antenna

After these photos were taken I added an important upgrade: I heat-shrunk some tubing to the ends of the cut coat hangers, to prevent cuts. (Evelyn caught herself on one of the ends.)

After everything was put together (Evelyn did all of it) we hooked it up to the TV. The results? It picked up every single digital TV station in our area, including ones we couldn’t get before. It got stuff that our purchased antenna, sitting in our bedroom, doesn’t pick up very well. A scrap of wood, some coat hangers, some leftover antenna parts, and we had something that outperformed any of that junk you find in the stores.

Even better, we didn’t have to make it pretty! Its signal is so good that we are able to stow it in a closet and attach it to the TV with a 10′ long piece of coax. Now there is no antenna visible in the room. Pretty cool.

If you would like to make one of your own, check out the Make blog. They have a video of how to make it and PDF plans. The Amazing Digital TV Antenna

Build bugs:

• The Make PDF mentions a 20″ piece of wood, then elsewhere refers to 30″. The length should be 20″.
• The measurement labels on the PDF are a bit confusing. Start in the center and work out.
• You must use metal coat hangers. If they are coated you MUST sand or grind off the coating at the junctions (where screws are). Even if the hanger looks bare it probably has a coat of shelac. Sand that off! Very important.
• The ends of the cut coat hangers are VERY sharp. Make sure to tape them off, or heat shrink some tubing to the ends. The tape won’t hurt the reception and will prevent you from getting hurt.
• You don’t need to use exactly the transformer they show. We had some of the twin lead to coax (male) laying around, so we stuck a coupler in the end so we could connect the coax. You want coax from the antenna to your TV tuner. (All convertors use coax.)
• About the transformer: You put the 300 ohm (twin lead) on the antenna side. You put the 75 ohm (coax) on the coax side. Twin lead for TVs is 300 ohms. Coax is 75 ohms.

Evelyn had a lot of fun putting this project together. It took an afternoon, cost next to nothing, and works really well. Give it a try if your rabbit ears aren’t working and you don’t want to spend cash on a piece of junk from the store.

Don’t know what it’s like elsewhere, but people sure aren’t staying in their bunkers here in Austin. Walked around on Saturday and most places were packed and the roads were busy. Churches and other places busy as normal yesterday. If people are “hunkered down” for the Dreaded Swine Flu, it sure isn’t happening here.