Need a remote control technology.

Although it won't go through Ali, infra-red is hard to beat on cost - using a modulated protocol (as used on TVs etc.), you can get an integrated receiver module for < 50 cents that handles all the analogue stuff and gives you a clean demodulated signal, and the transmitter is a few cents' worth of IR LED. Data rates of the order of 2Kbit/sec can easily be done - you can get modules which will handle faster rates. Look at

Anything else will be much more complicated and expensive.

It's also highly directional. You might want to try ultrasonic communications, using basically the same encoding methods as for infra-red signals, maybe.

You don't want these hassles. It is a major undertaking to add 802.11b to a product.

You are barking up the wrong tree. All these things are examples of protocols. A protocol does not penetrate aluminum. What you want is the physical communication channel. Nothing based on EM waves is going to penetrate aluminum except for very low frequency magnetic waves. I would look into ultrasonics. Sound will penetrate aluminum quite well.

-Robert Scott Ypsilanti, Michigan (Reply through this forum, not by direct e-mail to me, as automatic reply address is fake.)

How about the data transmitter using a digitized voice yelling the numbers out and the receiver using voice recognition? I can imagine people looking around trying to figure out where the voice is coming from. :-)

Thanks everyone for their input. It looks like i'll be doing either an infrared or cheap RF solution, AND probably requiring that some holes or vents be cut into the aluminum to expose the receiver.

As for garykato's proposal... I thought i was the only one being over-imaginative =) At one point i was thinking of putting a voice prompt, thinking of putting a DTMF generator/decoder, etc. to respond to user input, and probably putting a modem into the box. I guess that's what happens when i'm trying to make a simple device too high tech. Thanks for the thought though!

For minimum attenuation, the went should be more than a half wavelength long, but it can be quite narrow (1 mm). Thus, on 2.45 GHz (WLAN, Bluetooth etc.) the went should 8-10 cm long.

If this is too much, install a BNC socket facing outward in a small hole, solder a 1/4 wavelength wire to the to the centre of the socket (inside the container). Take a BNC plug and solder a 1/4 wavelength wire to it. Insert the plug into the socket and you have a passive repeater :-). With suitable BNC or N sockets, even moisture can be kept on one side of the wall, however, these do not usually tolerate any high pressure differences.

This works best if either station is close to this passive repeater, and even better, if at least one end of the link can be connected directly by a cable to this "repeater".

Paul