Max. length for cables for the AM2302

[JohanS]

Hi

I am trying to build something along the same lines as in http://learn.adafruit.com/dht-humidity- ... g/overview however with several AM2302's.

I now find myself wondering if I can have one Rasberry PI in the living room and long cables (up to 25 meters in some cases) to where I want to put the sensor, or if that length will make the sensor unresponsive?

So, is there any maximum length between the PI and the sensor, if so how long is that? If it is too short can I somehow boost it?

Best,
Johan S

[pmm]

I'm interested in purchasing this item but also need to know how long the cables can be.
Thanks

[adafruit]

We suggest no more than a meter

[JohanS]

Thanks for the reply! Do you have any clever and not to expensive solutions for how to use much longer cables if all I need is temperature and humidity? The time-resolution I need is... say 15 minutes or so, so nothing difficult at all...

Thanks a million...
Johan

[adafruit_support_bill]

For longer runs, consider using low-capacitance shielded wire. Another option is to avoid the wire entirely and use an XBee radio link.

[JohanS]

Hi again

Sorry for the delay in my answer. First of all thanks for the assistance. So let me see if I got this right.

To measure the temperature and humidity I would need:

1. An AM2302 - the sensor itself.
2. The XBee adapter PBC - to connect the AM2302 sensor to the wireless communication device. As how I understand this is needed.
3. A wireless device, I believe that the "XBee Pro Module - Series 1 - 60mW with Wire Antenna - XBP24-AWI-001" would be a good choice here, but I am not sure...
4. Some kind of power source, can I live with batteries perhaps?

So, assuming I am correct in the guess above and I buy these devices I will need some wireless device attached to my Rasberry PI in order to let it speak to these antennas. So I guess what I am asking is what am I missing from making this "work". I am looking for the best and cheapest (!!) option available Ideally I would like to use one sensor outdoors where sometimes it get far far below freezing (-25 C or so).

Sorry for asking so many beginner questions, but I am still a beginner at this..

Best,
Johan S

[adafruit_support_bill]

There is this wireless/XBee solution based on a different sensor: http://jdesbonnet.blogspot.com/2012/01/ ... ature.html
It should be possible to apply the same 'bit-banging' technique to the AM2302, but it would not be a beginner's level project.

The other approach would be to have a remote microprocessor (such as a Boarduino) read the sensor and transmit it back via the XBee. We have a library for the AM2302 that works on the Boarduino.

If you want to keep costs low and already have the AM2302, I'd get some Cat-5 Ethernet cable and see how far you can go with it. Cat-5 has 4 twisted pairs. Wire signal & ground on one pair and power and ground on another other.