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True if you want leakage, but for something like BEAM robotics, their transistors SUCK royally. Often times they arent even labeled correctly. Get your stuff from Digikey for quality (and inexpensive) electronics.

But will the quality be the same? Aren't the more expensive parts expensive just because they are designed for outer space use?

Well, Radio Shack electronic components have a reputation for being the very poorest quality. It is possible to acquire much higher quality components for similar or better prices at places like Digi-Key or Mouser Electronics.

Even if they did use the very highest quality electronic components available there wouldn't be much relative cost difference. If a resistor at Radio Shack is $0.10ea and a much better resistor is available from a real electronics supplier for $0.20ea then there's not going to be much of a difference when you need a dozen of them.

Digikey sells the Linx RF modules which cost $200-$250 for the evaluation kits with all the parts you should need. That's about as cheep as you will get. Note you will need some more hardware linke cases and power supplies. The EV kits just provide 9 volt batteries. Works for testing but not for long term use. After you get the physical link working, now you need to get the software working. That means more effort. Oh, as an after thought. If you are doing this for yourself (not a company) you need to get yourself a HAM license to muck about with RF devices. Otherwise if it's for work, go get only FCC approved devices. Dealing with the FCC regs will quickly cost more than the fancyest gear on the market.

Try one of these to change 12V into 5v instead of the free-built-in-coffee-warmer 7805. They generally do not need a heat sink. It'll set you back $20, though. They also have higher current units, but they aren't drop-ins (space permitting) for the 7805. You can buy them at Digi-Key.

As long as you are keeping the speed down (under 20 MHz or so) wire wrap works well, but as you go higher and higher in frequency, the added inductance and stubs of wire wrapping will kill you. Many of the newer parts are getting harder to find in DIP- especially as the pin count goes up. I don't know of any (modern) common part in a DIP package > 40 pins. On the other hand, 300-400 ball BGAs are getting common- imagine trying to wire wrap that! There is no real market in making a new quad XOR gate in DIP- that technology is mature- they won't really be able to improve on it, except possibly to make it faster, but a DIP package has leads, and leads have inductance, and inductance kills high frequencies, so by default, if you are improving the speed on an IC, you need to shrink it and go to SMT. They are also trying to cram more into a chip, but that implies a greater pin count- again, which pushes you to SMT.

But, as the person who posed the question implied, SMT is difficut for a hobbiest to work with. One alternative is to make your own PCBs, either by etching them at home, or go to some place like APCircuits where you can get prototype PCBs made pretty cheaply. And one hint- if you are doing SMT, get the solder mask, it will make your life very much easier.

I still wire wrap when I need to- and Digi-Key has had most of what I've needed, though the little pins to mount discrete components are outrageously expensive. (In particular, the T68A bifurcated pins, with room for 3 levels of wrap, at $92.25/1000.)

Their catalog is browsable based on categories, from product to manufacturer, and online in Acrobat format:

• Individual catalog sections
• Switches section of the catalog (bottom of the page)
• Entire 698 page catalog (This is a link to the actual .PDF (28 MB!) catalog)

Good luck -- I have a case I have to convert from AT to ATX power (thankfully, the motherboard isn't changing -- it's one of those dual-power ones). Thus I need to replace the big honkin' power switch on the front with a little momentary that'll connect with the motherboard. Fun, huh? I was worried until I found this place.

Their catalog is browsable based on categories, from product to manufacturer, and online in Acrobat format:

• Individual catalog sections
• Switches section of the catalog (bottom of the page)
• Entire 698 page catalog (This is a link to the actual .PDF (28 MB!) catalog)

Good luck -- I have a case I have to convert from AT to ATX power (thankfully, the motherboard isn't changing -- it's one of those dual-power ones). Thus I need to replace the big honkin' power switch on the front with a little momentary that'll connect with the motherboard. Fun, huh? I was worried until I found this place.

Their catalog is browsable based on categories, from product to manufacturer, and online in Acrobat format:

• Individual catalog sections
• Switches section of the catalog (bottom of the page)
• Entire 698 page catalog (This is a link to the actual .PDF (28 MB!) catalog)

Good luck -- I have a case I have to convert from AT to ATX power (thankfully, the motherboard isn't changing -- it's one of those dual-power ones). Thus I need to replace the big honkin' power switch on the front with a little momentary that'll connect with the motherboard. Fun, huh? I was worried until I found this place.

Their catalog is browsable based on categories, from product to manufacturer, and online in Acrobat format:

• Individual catalog sections
• Switches section of the catalog (bottom of the page)
• Entire 698 page catalog (This is a link to the actual .PDF (28 MB!) catalog)

Good luck -- I have a case I have to convert from AT to ATX power (thankfully, the motherboard isn't changing -- it's one of those dual-power ones). Thus I need to replace the big honkin' power switch on the front with a little momentary that'll connect with the motherboard. Fun, huh? I was worried until I found this place.

"Presentation" is so damn annoying that some of us install Junkbuster just to get away from it. Radio Shack might have a nice presentation, but they've neglected to make a searchable catalog.

On the other hand, Digikey's catalog page has little presentation, but their catalog is actually useful.

Commerce isn't about fluff. Commerce is about meeting a need that your customer has. Maybe retail stuff needs some fluff to get average Joe into the store, but in case you haven't heard B2B is where it's at. When IBM is buying 10 million resistors to put into a power supply, they will probably not go to Radio Shack.

"Presentation" is so damn annoying that some of us install Junkbuster just to get away from it. Radio Shack might have a nice presentation, but they've neglected to make a searchable catalog.

On the other hand, Digikey's catalog page has little presentation, but their catalog is actually useful.

Commerce isn't about fluff. Commerce is about meeting a need that your customer has. Maybe retail stuff needs some fluff to get average Joe into the store, but in case you haven't heard B2B is where it's at. When IBM is buying 10 million resistors to put into a power supply, they will probably not go to Radio Shack.

I have to say that this is your best bet, because it doesn't rely on line of sight, doesn't mess with 802.11, and is cheap. Also, because RS232 is the standard for many types of telemetry, it will most likely work with whatever data-gathering equipment you use. It is up to you which model and quality to use, based on your budget and other requirements.

You might check http://tflow.com/boards.html (bottom of page) for a start -- they have prices on their page. These prices are about what to expect anywhere you go. We, however, went through ABACOM Technologies when we got one of our radios (the cheaper, but very functional one). Their webpage is somewhat substandard, so you might not find the RS232 radios on it. I know that they sell them though, and you can call them asking for P/N RTcomTx-RS232 (Transmitter - $87.15 canadian) and RTcomRx-RS232 or (Reciever - $105.52 canadian). There are tons of other places to get it from on the net (digikey *might* have some, but I haven't checked).

For parts, I would try Digi-Key or JAMECO.

This is at least two years old. It's been around for a long while.

PICs are great little microcontrollers. Get one from DigiKey for around $6. A good programmer for them you can build is called the NOPPP. It's easy and cheap to build.

This guy built a better version of the propeller clock.

Hope this helps.

Did I miss a rash of computer sales?

Yeah, you did. Computers are in *everything* these days. Cell phones, PDAs, pagers, games, notebooks, PCs, etc. have all been selling like hotcakes. Demand for consumer electronics has grown across the board, and component suppliers haven't kept up. Capacitors, RAM, and CPUs have particularly constrained supplies.

Try searching Digi-Key for a popular capacitor, like the Panasonic ECU-V1H104KBW, a 0.1 microfarad ceramic chip cap. "Quantity Available: 0 - Check Lead Time". Or try to find surface-mount tantalum capacitors in stock. I just tried >50 popular values, and *nothing* was in stock. The handheld electronics people have sucked them all up (cell phone designers in particular like tantalum caps). This isn't a new phenomenon -- I haven't bothered designing a tantalum cap into a board for at least six months, and the situation is only getting worse.

A few months ago, I had to redesign because a Fairchild *transistor* was unavailable. A few square mm of cheap silicon, and even it had constrained supply. <grumble> I'm starting to get bitter about having to redesign circuits because we can't get a particular part. If I find that a cheap resistor is unavailable, I'm gonna cry. ;-)

And just a few days ago, a colleague told me that Atmel AVR processors will be unavailable until the end of the year. It seems one got designed into the PS2. I feel sorry for the poor bastards who bet their products on that device.

I ordered a DVD from CNL on the 21st and received it yesterday morning without a hitch. Pretty good considering I'm at the extreme other end of Canada. What makes that interesting was the fact that I opted for Canada Post over UPS. Not only was it much cheaper, but UPS doesn't actually operate here and the minimum time I received a UPS package was about a week. I wouldn't have received it in time. Maximum time? A month. Ridiculous, even the USPS is much better than that.

I also made an order from Digi-Key which came in 3 days, despite the fact that I live in Canada. Probably had something to do with the fact that they let me use Purolator.

As an aside, with many people having DVD players nowadays, Christmas shopping has never been easier. I got three today: Pink Floyd's The Wall (awesome DVD, very well put together with tons of extra features), Jimi Hendrix: Live at Woodstock, and South Park.

Needless to say, I'm happy. I'm inviting some friends over tonight to watch The Wall (twice, the second time around with commentary by Waters and Scarfe) and drink a lot of booze.

Use gold contacts. You can also get fully sealed contacts. Get a DigiKey catalog, look through the contactsd section, they have waterproof contacts. Place all contacts on the bottom of the box so if they do develope a leak it still won't leak into the box. Take a look at a telephone company box on a telephone pole. They aren't even water proof. They are just designed to shead water well, and if water makes it into them, they have a clear path for it to exit without it going over any circutry. As for what I'd use, I'd look at using the heavy plastic electrical boxes designed for outdoor use. Grainger has them (you should be ale to order through them as the community or as a busisness).

My concerns: Heat, Power, Size, Antenna, Software.

• Heat: You need to make sure the you have enough ability to get rid of the heat generated in them so they continue to work over the summer.
• Power: Is this network supposed to continue to work if the power goes out? If so you will need some sort of battery backup. The other power issue is related to the heat generated... The more power hungry your system, the greater the heat load from the power supply. Use a good quality switching power supply, not a cheep PC one.
• Size: The larger it is, the easier it is for someone to hit with a rock/etc. Also the more tempting it is as a target.
• Antenna: Where will it be located? What type? If it is inside the box then the box can't be metal. If it is outside the box, then that requires yet another waterproof connector. If it has to be located on top of the box then that is a possible source of a leak. Make sure the internal antenna wire dosen't funnel water onto the PCB.
• Software: What software are you going to run to provide the roaming abillity provided by the access points?

Things I would do:

• Use all commodity parts that have atleast three different manufacturers that make them.
• Try to find a manufacturer of RF Lan access points that has an environmentally hardened access point. If so use it, and forget the rest of this list, and possibly the triple source requirement too.
• Keep the parts count down.
• Look for components that can handle as wide of tempeture range as possible.
• Use a Single Board Computer with PCMCIA card slot. Look for a board that has an analog to digital converter so you can hook up a thermalcouple and read the current tempeture. Digital output lines for controlling a small heater and air circulation fan. The parallel port or unused serial port can also provide digital output lines. Look for hardware monitering equipment like found on modern motherboards. This would be helpfull for detecting failures of one system (like the cooling fan or heater) that may lead to a more costly failure and service outtage latter.
• Use all solid state design. This means using a flash memory disk instead of rotating. This is better for hot and cold conditions.
• PCMCIA RF Lan card of commodity design that can use an external antenna.
• Try to mount the antenna on the bottom side of the box if the box will be set with any altitude.
• If needed look into having a heating element in the box to keep it's tempeture high enough in winter. Typically this can also be hooked into a dew sensor to warm the box to keep dew and frost from forming on it. Most electronics are specified for a non-condensing environment.
• If summer heat will be a problem, use an alumimum enclosure and a fan to circulate air within the enclusure. If needed one can go to peltier junction heat pumps, but this is an increase in complexity and expense. It may be better/cheeper to get components that meet military tempeture specs.

DigiKey has some devices called DC to DC converters/power supplies. Something like that. The 25W one (most powerful one they have) outputs 5 and 12 volts. I'm not sure if 25W will be enough, but its more than IC's tipically can handle, and you could use more than one unit.

Or, you could try voltage regulators and capacitors connected to computer style power connectors.