Simple Wireless Arduino Multimeter

[Thane of Cawdor]

Hi everyone,

I wanted to make a wireless multimeter (really a voltmeter) out of two arduinos, one to transmit the data and one to receive so I can measure voltages from across the room . I was hoping to connect the receiver to an LCD (simple 16x2). The analog input for the transmitter microcontroller would simply be a voltage divider. I wanted to know which wireless module/system I should use (easy and cheap preferably) and how I would encode and decode the data coming in and out of the modules.

Many Thanks

[Thor-Arne]

You don't say anything about the distance between the modules, assuming short distance, have a look at the NRF24L01 modules.
These are quite available and inexpensive on ebay and there's tutorials on the arduino playground.

[Richard Crowley]

There are Arduino-like products with built-in wireless.  My favorite is Moteino. It is the size of a postage stamp and has a great wireless module.
They include a pretty robust wireless protocol driver.  I used the more powerful RFM69 wireless modules.  Recommended.
I recently used 6 of them for a wireless tally-light system for a multi-camera studio. 

http://lowpowerlab.com/moteino/

[w2aew]

There are Arduino-like products with built-in wireless.  My favorite is Moteino. It is the size of a postage stamp and has a great wireless module.
They include a pretty robust wireless protocol driver.  I used the more powerful RFM69 wireless modules.  Recommended.
I recently used 6 of them for a wireless tally-light system for a multi-camera studio. 

http://lowpowerlab.com/moteino/

I like the Moteino too. I did a short video review of these modules last year...

[Thane of Cawdor]

Which one of  the  transceivers would be the simplest to interface to an Arduino?

[Thor-Arne]

I can only answer for the NRF24L01 modules.

These are simple to interface, and there's libraries readily available so coding needed to get it running is minimal.

Just google arduino nrf24l01

[w2aew]

Which one of  the  transceivers would be the simplest to interface to an Arduino?

Those Moteino devices are BOTH and Arduino compatible platform, PLUS the wireless transceiver.  No need for another Arduino.

[Richard Crowley]

Which one of  the  transceivers would be the simplest to interface to an Arduino?

There are libraries for the HopeRF RFM12B and RFM69. 
For example here are the software for talking to the RFM12 from Arduino modules made by...
LowPower Lab ("Moteino") http://lowpowerlab.com/moteino/#programming
and JeeLabs ("JeeNode")  http://jeelabs.net/projects/jeelib/wiki

Google returns >6000 hits for: RFM12 Arduino library

[Thane of Cawdor]

Thanks for all the responses, I will look into each module and see which one is best suited for me.

On another note, I have seen many projects where the transmitter would send a single character and get an LED or another output to turn on the receiver side. Is it possible to transmit the analogRead value instead of a single character somehow?

Thanks

[Richard Crowley]

Sure, It will do whatever you program it to do.  Your DMM, and the Arduino, and the wireless link only operate on ones and zeroes,  There is no fundamental difference between "a character" and a reading from your DMM.

[Thane of Cawdor]

Since I only require the Tx line of the transmitting Arduino, can't I just connect the data line of the module to the Tx pin of the microcontroller and connect the other module to the Rx pin of the receiving Arduino?


Thanks

[linux-works]

I use and like the zigbee (xbee) modules.

its just rs232 that is wireless, in transparent 'easy' mode.

one cool thing that can be useful: if you have several stations tuned to the same channel, when one transmits they all hear it, so its like a poor man's multicast.

create a packet format where each station has a src and dest addr and you really can do multicasting that way.

[Richard Crowley]

Since I only require the Tx line of the transmitting Arduino, can't I just connect the data line of the module to the Tx pin of the microcontroller and connect the other module to the Rx pin of the receiving Arduino?

Sure, if you are going for cheap and dirty. And zero fault-tolerance.  You scheme would work in a perfect world. But here in the Real World, we have noise and interference, and wireless data transmission uses techniques to provide reliable communication even in in a hostile environment.

[MLXXXp]

Since I only require the Tx line of the transmitting Arduino, can't I just connect the data line of the module to the Tx pin of the microcontroller and connect the other module to the Rx pin of the receiving Arduino?

Sure, if you are going for cheap and dirty. And zero fault-tolerance.

You can add fault-tolerance to this scheme just by adding a checksum or other form of verification to each message. If the messages are transmitted often enough, and duplicated if necessary, the receiver can just ignore messages that don't verify. You could even add information to the message to allow some error correction, if you wish.