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[on:]

So I have been wondering about wireless sensor networks and home automation for a while. I wanted to know how low I could really push down the price of bi-directional sensor network.

I have these specifications:

• Each node costs less than $6, not including battery
• Each node lasts at least three months on an NiMh AA.
• Bi-directional, data rate not important
• Star topology - one master. Mesh network not necessary, but would be nice.
• Max range 100m

As far as I can tell, using XBee + Arduino just to measure an analog value is complete overkill at ~$45. I hear you can use Xbees by themselves but they are still expensive. Is there some cheap hardware built just for this purpose?

[Reply #1 on:]

Nordic Semiconductor.

[Reply #2 on:]

Aha. I have noticed that the nRF24L01+ IC is very popular and pretty cheap, but it is not a single chip solution. I suppose I would combine this with an ATtiny or a really small ATmega328 and have my single-board wireless sensor node?

Either that or use the 8051 CPU that I have no experience with in the single-chip nRF24LE1, which I found on their website. 

I am mainly looking for someone who has done this with this pricing in mind before. It seems that everything I read about Arduino sensor networks involves the Xbee + Fio or some variant.

[Reply #3 on:]

Nordic makes chips with a 2.4 GHz transceiver and 8051 on the same chip. TI makes similar devices.

[Reply #4 on:]

I saw those Nordic SoC's with the 8051.  Was kind've curious about them.  Does anyone know how easy/simple it is to pick up 8051 development?  (Looks like Nordic does supply SDKs et al, so maybe I should look at them and answer my own question...)

[Reply #5 on:]

Also FWIW, Atmel does make an ATmega with integrated 802.15.4 (ZigBee protocol)... the ATmega128RFA1.  Not sure if anybody's built one out with Arduino IDE support yet.

http://www.atmel.com/devices/ATMEGA128RFA1.aspx

Sadly, they only come in QFN form factor, so us DIY'ers aren't going to build our own boards unless we're the adventurous hotplate reflow soldering types...

[Reply #6 on:]

8051 development is about the same as with any other MCU.

[Reply #7 on:]

So why not take a module like this

2.4GHz Transceiver Low Power nRF24L01+
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=188

and mate it to uC board with minimal components and connections to a battery?

[Reply #8 on:]

Those are the modules I use, they are available very cheaply from several suppliers on Ebay. I'm using them with PICs.

[Reply #9 on:]

So why not take a module like this

2.4GHz Transceiver Low Power nRF24L01+
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=188

and mate it to uC board with minimal components and connections to a battery?

Very interested in these parts. I saw them for sale on iteadstudio.com and they mentioned one can receive up to 6 senders. I wonder if I can have one receiver receive more than 6 senders or have 2 receiver receive up to 12 senders. Does the chip work that way? How does the chip identify senders? Thanks.

[Reply #10 on:]

Luidr,
Do some reading for more info.
http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo
I have not tried them myself.

[Reply #11 on:]

DUL radio (http://www.digitalurbanliving.dk/news/news/dul-radio.php) uses this nordic chip. It has a base station which can communicate to up to 4 "sensor boards". In theory the boards can also communicate amongst each other, but I dont think they have it implemented.

[Reply #12 on:]

Luidr,
Do some reading for more info.
http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo
I have not tried them myself.

Very interesting little chip! I'm reading the shockburst mode. Neat! I'll have to read more and play with it. Will report back what I learn.

[Reply #13 on:]

So I have been wondering about wireless sensor networks and home automation for a while. I wanted to know how low I could really push down the price of bi-directional sensor network.

http://shop.moderndevice.com/products/jeenode-kit

The JeeNode (kit) at $18.90 in lots of 10 is a bit more expensive than you wanted but a lot less than $45.

That is all on one board, and uses 3.3V which means it will have low power consumption.

[Reply #14 on:]

I will take a look at the Nordic nRF24L01+ modules considering I already have some. I was hoping for a one-chip solution that could provide mesh networking of hundreds of nodes that cost less than $6 per node, since each node only has to measure a an analog value.

The Jeenode does not fit this requirement. Ironically, they wanted to provide a product that is not overkill, but didn't balance their equation right. They replaced the very nice Xbee with a bare radio antenna, which leaves you to implement all communication in software. They should have reduced both the microcontroller and radio module, but instead they axed both price and nice features of the radio module.