NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Project Help and Ideas » Help with determining components

December 01, 2010
by Hexorg
Hexorg's Avatar

Hey everyone... I got some neat idea that requires transmission of data at the distance of a household (say 100ft). The rate of transmission doesn't have to be big, maybe 1 byte per second. Each device should have transmitter and receiver though. My main concern is the size and cost, and easiness to connect.

Wires sure are small in connection, but connecting say 20 devices all over house will get tangled and ugly. IR wont go through walls :/ Bluetooth is too low distance

So I only see RF and some variation of WiFi.

Wifi, from what I understand has kinda big antenna. I found a few people mentioning this wireless serial interface on this forum, but the antenna is big and rigid. I was hoping to incase each device in a box inside wall outlet, so about 2"x0.5". Could I replace the antenna in the link above with the same length wire?

So I'm left with RF. I know a simple wire can work as an antenna. I can just drag that wire outside the device case.

My questions are - can you think of a better way then RF to acheive this transmission? Maybe you happen to know some good IC that can broadcast and receive low bandwith digital data, having a wire as an antenna? Or maybe you know a good article about making an RF reciever and transmitter that can broadcast and receive low bandwith digital data, having a wire as an antenna?

December 01, 2010
by rajabalu21
rajabalu21's Avatar

I could think of one more option. Check out this. And you can find more details on how to interface that to the microcontroller see this. You just need a couple of RFM12B and then you can interface that to your nerdkit.

-Raja

December 01, 2010
by bretm
bretm's Avatar

Another option, since you mentioned an electrical outlet and 8 bits per second, is to use the power lines inside your walls. It may not be a great solution because the transformer makes it bulkier, but it's an option. Search for "power line carrier" for info about it. There's this for example.

December 01, 2010
by Ralphxyz
Ralphxyz's Avatar

How much do you want to spend?

I am trying to learn ZigBee to do this but the cheapest I have found so far is around $17.00 for a Digi module than add a mcu and a sensor and you probable are looking at $25.00 per location. Or you could go with ATmel using a AVR ATmega128RFA1

But of course since ATmel closed it's own fabs nobody has any ATmel processors in stock. The ATmega128RFA1 cost around $6.00 and has the processor and ZigBee RF module all in one.

I have both the Digi module and the ATmega128A1 that I am trying to use to learn ZigBee.

If you want to use house wiring then there is always X-10. You will often find X-10 modules at yard sales.

So what are you gonna do with 20 devices?

Ralph

December 01, 2010
by Hexorg
Hexorg's Avatar

rajabalu21, that seems perfect! small size low power consumption.. At the first glance i cant tell the range, i'll look in it later, thanks!

bretm, well i was thinking to use a transformer + rectifier to drive the thole thing anyway, but only part of the devices will be in walls, others will be far from power lines, thanks for the idea though!

Ralphxyz, ZigBee seems interesting, but I get a feeling that it's too much for what i'm trying too make.

The reason for all this is a sort of smart house.. kinda... I saw many ideas and implementations, up to assigning an ip address to each of the light sources in the room... but a dhcp client + tcp/ip controller + mac controller just to turn a light on seems too much. What I'm trying to do is a little chip (client) that you can plug in between the wall switch of the lamp, that would get the power from wires that are already there, and control the lights through RF info it receives from the main controlling unit(server). A client can be connected to a light, or some other device, for example a coffee maker. Host, on the other hand can just tell, hey you, do command N, and so on.

December 01, 2010
by rajabalu21
rajabalu21's Avatar

Sounds like an interesting project. Keep us posted on your progress. At 433 MHz the range is > 150 meter as per datasheet. However, I doubt that you will get that much range inside the house. I suppose you could configure some of the modules are repeaters if you run into range issues. All the best!

-Raja

Post a Reply

Please log in to post a reply.

Did you know that interrupts can be used to trigger pieces of code when events happen? Learn more...