Help With A Wireless Project

I have an LCD and an Arduino on one board, and a MOSFET controlling a fan and a temperature sensor on a separate board. Between them there is currently a +5V wire, GND, MOSFET Logic, and Sensor In line.

My client now wants me to find a way to kill the wires. But from what I'm finding, the only 433MHz transmitters support one line of data.

I know this isn't hard or something that requires me to use some crazy overkill IC. So I was wondering what you guys would recommend. Wireless is a bit out of my jurisdiction.

Grazie :)

The 433MHz devices are one-direction and someone else said they don't work very well when paired for bi-directional use.

The NRF24 2.4GHz transceiver modules are bi-directional and cheap and easy to use.

...R

Look at Robin2’s serial input basics serial lnput basics

The nrf24 radios don’t use serial, but the referenced thread may give some hints on how to build, send and receive the data packets. If you want to use serial the APC220 transceivers are pretty easy to use and look like a regular serial port and have better range (1000 meters claimed).

Robin2: The 433MHz devices are one-direction....

This is only true for the really cheap ones. 433MHz devices are also available as transceivers i.e. bi-directional.

aisc: 433MHz devices are also available as transceivers i.e. bi-directional.

Interesting. I have never come across one. Do you have a link ?

...R

http://www.seeedstudio.com/depot/433Mhz-Wireless-Serial-Transceiver-Module-1-Kilometer-p-1733.html

Theres also a slightly cheaper and less powerfull equivalent version, the HC -11 of which I just received some but havnt as yet had a chance to play with them. http://www.ebay.com.au/itm/like/131553843611?limghlpsr=true&hlpht=true&ul_noapp=true&hlpv=2&chn=ps&lpid=107&ops=true&viphx=1

Robin2: Interesting. I have never come across one. Do you have a link ?

...R

The TI CC1101 modules are probably the most reknown. eBay has a fair few sellers with quite a fair selection

Thanks. I have bookmarked the links.

...R

I also have two lines of data I need sent back and forth, not one like most of these support. What are my options then? Thanks :)

dominicluciano: I also have two lines of data I need sent back and forth, not one like most of these support. What are my options then? Thanks :)

Treat it as 2 separate messages ?

What exactly do you mean by 2 lines? If you just mean several words with a LF character in the middle you can easily write your software to deal with that as a single message.

Have a look at how the data is organized in the 3rd example in Serial Input Basics. The choice of start- and end-markers should allow for most "special" characters to be part of a message.

Another option would be to replace the LF character with something else before transmission and convert it back after receiving the data. However using start- and end-markers will make the system more robust.

...R

What I mean is I have two IO lines, and it looks like a lot of these only support one IO line. I don't want to have a total of 4 transceivers just to make this work wirelessly.

Neither of those IO lines is sending anything to an LCD. One is sending a logic high to a MOSFET, the other is sending information to the ADC of the MCU

Theres no easy way to do what you want without having some kind of small micro on the 2nd board. An ATtiny would be all thats needed, and a 433 Mhz transceiver. How often does the sensor send data ?

could you just read this sensor directly on an Xbee?

You could use a SoC transceiver - it is a transceiver+MCU on a single chip. Atmel have some, so do TI.

mauried: Theres no easy way to do what you want without having some kind of small micro on the 2nd board. An ATtiny would be all thats needed, and a 433 Mhz transceiver. How often does the sensor send data ?

I was planning on having an MCU on each board. And a transceiver on both. We were figuring it'd be cheaper to design the PCBs normally from scratch, and then just put ports on both to connect each to a 433MHz transceiver board you find on eBay or something.

The sensor is an NTC thermistor. You put 12V in and the resistance increases or decreases with temp, and then the ADC on the MCU reads the voltage on the other side (through a voltage divider clamped at 5V with a zener). To answer your question, it can read anywhere from continuously to probably about 10 samples every three seconds. I'd prefer it to be more like once per second, but I'd settle for a few seconds

aisc: You could use a SoC transceiver - it is a transceiver+MCU on a single chip. Atmel have some, so do TI.

I ordered an 8051 chip with 2.4 Ghz on it. I'll play with that a bit when it gets here.

dominicluciano: What I mean is I have two IO lines,

I think that makes it simpler.

Maybe I misunderstand the requirement but it seems to me that you want ArduinoA to send two pieces of data to ArduinoB to mimic what currently is done using two wires. You could send dozens of pieces of data in one wireless message.

...R

Robin2: I think that makes it simpler.

Maybe I misunderstand the requirement but it seems to me that you want ArduinoA to send two pieces of data to ArduinoB to mimic what currently is done using two wires. You could send dozens of pieces of data in one wireless message.

...R

I think a part of the issue is OP, by his own admission, was out of his depth and "has been learning on THIS job", so he had trouble conveying his requirements. He seems to have the hang of it now - I guess we were all novices at some point...

Its a bit more complex. The 2nd board has a MOSFET controlling a fan and a temperature sensor on it, so the 2nd board needs a digital signal to it from the 1st board , and the sensor sends data from the 2nd board to the first board. Thats a hard ask to do with radio without adding some smarts to the 2nd board.

I think I had assumed (probably incorrectly) that the Original Post described a system with Arduinos on two boards.

...R

Hi,

You could do this.

Tom… :slight_smile: