Possible for a circuit to fit in this size space?

[bobengr]

Not being a circuit designer, I don't know if the following is possible:

I want to have a circuit board that has two sensors - temperatue and barometric pressure - and an RF transmitter in the 300-400 MHz range to send the temp and press data to a receiver up to 20 feet away. The board must fit in a volume of 2.75" x 1.75" x 0.75". I want the data to be sent every 1 seconds, so I think two RF data channels are required.

Is a board with these specs possible? Will two RF channels be required, or can one be used to save space and cost?

Thanks!

--Bob

 

[Comcokid]

You should only need a single transmitter. Several bytes of data needed for each sensor, plus additional bytes for a preamble (syncronizing), ID, checksum, etc will only take a few milliseconds even at a slower data rate.

Some pre-made RF modules have an on-board temperature sensor. Many of these are the size you give, or smaller.

Many of these modules are design to transmit in one of thethe ISM band (Industrial Scientific Medical) frequencies. For the range you need, there are some around 400 MHz (can't recall the exact ISM frequency assignments around there) or the 868 MHz (Europe), or 900-925 MHz (North America) bands.

The most basic use ASK modulation which in some situations may not provide enough noise or communication robustness but are the least expensive, but may be fine for your short-range needs. Remote car locks are usually ASK. More capable modules use FM or FHSS modulation. Even better modules with more range than you need will be full transceivers and use a digital modulation method, and may just state 'digital spread-spectrum', or be built to a standard such as 802.15.4/Zigbee or such.

There are many module manufacturers out there. Search around and I'm sure you will find a module pair (transmitter and receiver) that you can try for your application.

 

[VEBill]

Such 'weather stations' are a common consumer product. The only difference is that they typically have the barometric pressure sensor in the base unit. At the very least, review the technology used.

 

[MacGyverS2000]

Doable without even thinking about it... that's a pretty large area, actually, for what you need to do it with.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[imcjoek]

Not exactly industrial grade, but you can poke around Sparkfun for a bit as they have a lot of small wireless breakout boards. At least will get you into a ballpark.

http://www.sparkfun.com/categories/16

 

[bobengr]

I'm the OP, and I appreciate the help you have all provided. The confirmation that the sensors/transmitter will fit in the available space allows me to focus on some other details of the design. And, it's good to know that a single RF channel will suffice.

Thanks!

--Bob

 

[IRstuff]

You could use Bluetooth for this application. The USB Bluetooth transceivers are absurdly cheap:

http://www.ebay.com/sch/i.html?_fro...luetooth+usb+dongle&_sacat=See-All-Categories

TTFN
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