wireless data transmision help totaly new to this

Ok i want to build a closure logger. its basically a telescopic tube that is pinned between a roof and the floor. When the roof moves down this devices measures the amount the roof has moved down relative to the floor. the way this device works is not so important right now but what is important is that i need to record this data over a few months, maybe store it on a memory card on the device. Then i must retrieve this data from a safe distance, so i will need to transmit it wirelessly. it must be done wirelessly from approximately 15meters or so. I want to use a stand alone arduino atmega328 microcontroller in the unit that measures the movement and i will also want to use a atmega328 in the unit that receives the data.

The picture bellow is a real basic concept of what i want to do. For example once the device has been in place and it has recorded movement over months i want to go in the approximate range and push a button basically then the device must send all the data it has recorded over the months to the remote unit which can then save the data on a memory card and analysed on a computer.

i am asking for help regarding the data transmission, i do not know how to even begin. i know nothing about what hardware i will need, i know nothing about wireless serial communication. Can someone please nudge me in the right direction as i would like to not waste time researching on the incorrect stuff.

calvingloster:
it must be done wirelessly from approximately 15meters or so. I want to use a stand alone arduino atmega328 microcontroller in the unit that measures the movement and i will also want to use a atmega328 in the unit that receives the data.

On the face of it a pair of NRF24s for short range arduino<>arduino communication. Cheap and well-established.

But why do you want to send the data to another Arduino, and what happens to it after it gets there? It might be better to send the data directly to device that can make better use of it.

This is for applications in dangerous area’s so the information must be sent wirelessly if that makes sense. And the unit that receives the information must be small to carry and run by batteries. So basically the remote receiving unit will be carried by a person that will walk to the dangerous area then push a button, receive the data from the device measuring the movement then the person will go back to the office and download the data.

i hope this clears it up for u?

So, low power one-way comm's are all that is needed. Equivalent of a promini and 433 MHz Tx module is all that is needed. Here's one setup as RF remote control. 8 MHz promini runs a month on 1000mAH LiPo battery - stays in power down sleep mode until a buttom is pressed. Uses MAX1811 to control battery charging when connected to 5V source. Easily transmits 50 feet (the length of my fencing club) with simple 17cm 30 guage wirewrap wire as an antenna - you can see a piece of white wire snaking along the right edge and along the bottom, ending at the lower left screw. Strip the Promini to minimal parts - no regulator, no power on LED, power down the Tx when not in use, same with your sensors - can get power draw really low.

Rx module can be similar with mating card, SD card, bigger battery as it needs to be awake all the time looking for a message from the Tx module.

Ok kewl so i see u say u use the promini, but i use the bigger atmega328pu chips but im sure its the same thing right? ur will just use less amps? can you maybe explain to me on a very basic level how the transmitter communicates to the receiver? like as if i was 8 years old haha

Same processor, different package. Promini leaves off the USB/Serial adapter & only has small 5V regulator, no auto power switching - so just a stripped down Uno.

Read the VirtualWire documentation for Tx to Rx explanations to start. I'm not gonna duplicate all that: http://www.airspayce.com/mikem/arduino/VirtualWire.pdf Code examples used to be in the document, are on the website now.

calvingloster: This is for applications in dangerous area's so the information must be sent wirelessly if that makes sense. And the unit that receives the information must be small to carry and run by batteries. So basically the remote receiving unit will be carried by a person that will walk to the dangerous area then push a button, receive the data from the device measuring the movement then the person will go back to the office and download the data.

i hope this clears it up for u?

It goes nowhere near clearing it up. Indeed, it gets worse - and that's without quibbling why it must be done by wireless - and I think you are jumping to conclusions.

An information receiver that must be small and run by batteries sounds like a pretty good description of a phone to me. That makes the price and painlessness of Arduino+bluetooth to Android phone extremely tempting. What this means is pushing a button on a device you might already have, or can be purchased for $50, using an app written by somebody else for free to collect data off the Arduino's SD that you then can transfer anywhere by any means you like, or even review thereon, and on site, if you need to. Using the HC-05 bluetooth module like I do would be stretching the friendship over 15m but I understand the low-energy HM-10 module is good for 100m.

How far does the person walk? If it isn't too far, his desk could be in bluetooth range and Arduino talks directly to the PC. It might be out of bluetooth range but still within the local WiFi network, so use that and achieve the same end. The result in both cases being no phone, no downloading, and no walking either.

Is the walk so long that the person would actually prefer to drive? OK, so it's out of range for both bluetooth and WiFi, but the chances of still being in mobile phone range might be good, in which case Arduino+phone module could be just what you need. You could even have it send you a text if the roof sags while you are out surfing. ET never had it so good.

Hence my question...........

I think it is fair to say that sending data Arduino to Arduino is usually something you only do as a last resort.

Then i must retrieve this data from a safe distance, so i will need to transmit it wirelessly.

That doesn't follow. You can easily transmit information over cheap telephone wire, for hundreds of meters, without any special effort at all. If you can place the measuring device in the dangerous spot, you can run the wire at the same time.

If you wanted to send information over several kilometers of wire, that would take a little effort.

I support the bluetooth idea. Cheap, no need for long wires, and two way. You only download once a while so the one way radio is not gonna work. Write your program so it takes commands from serial port and sends the file. Then just use a bluetooth terminal app on android and type in command and receive the data. Start with getting a bluetooth module and test range with realistic situation. If it reaches enough distance, then it is good to go. Don't start with writing the code and then realize bluetooth can't do it. Next solution is xbee, much greater distance and more suited for this type of work. Just a bit more expensive.

I see this as three devices:
Inexpensive 433 MHz TX only that goes in dangerous location.

Inexpensive 433 MHz Rx to receive and store on SD. Same card can have whatever to send “long distance” to data manipulation site.

There are machines and very confined spaces where this logger will be placed. it must be easy to install without wires. It is used for underground in mines so u cant exactly drive to the site. things get very complicated underground with regulations on electricity so i need the units sealed and meshed to prevent methane ignition. I want to use two arduino's because i have learnt to use them and they are very flexible. CrossRoads seams to be on the same page as to what i was thinking of doing i must just research on those units as i dont think they will be available in south africa. Keep in mind that the people using these devices are not so clever so a simple one button push will be as complicated as it can be,

Is it just one device in the whole mine or do you intend to have a number of them? If you want a number of them, then you may want xbee radios. You CAN purchase them anywhere in the world. Then you may install additional devices and they expand the network, no need to set up during installation. Then you have the xbee radios send data continuously to a gateway and the gateway forward everything to a safe location outside the mine, maybe using a cellular network since I don't imagine miners have wifi just laying around. This solution is scalable (add more devices etc.) while others are not. Plan ahead the extend of your project, whether it is one device or a number of them.

Check with Boffin1, he seems to have good suppliers for Arduino related things is SA.

liudr: Is it just one device in the whole mine or do you intend to have a number of them? If you want a number of them, then you may want xbee radios. You CAN purchase them anywhere in the world. Then you may install additional devices and they expand the network, no need to set up during installation. Then you have the xbee radios send data continuously to a gateway and the gateway forward everything to a safe location outside the mine, maybe using a cellular network since I don't imagine miners have wifi just laying around. This solution is scalable (add more devices etc.) while others are not. Plan ahead the extend of your project, whether it is one device or a number of them.

No there will be many units all over the mine. The mine is spaced out over a large distance, probably 6km to 8km underground. Making a large network will be to complicated and unpractical. i appreciate your suggestion though.

I thinks your biggest problem will be sub surface TX as the 433/nrfs are A) Low power B) Line of sight ?.

8)

ESSEF: I thinks your biggest problem will be sub surface TX as the 433/nrfs are A) Low power B) Line of sight ?.

8)

Ok so won't radio frequency work underground or what? I know they use low frequency signals for vehicle collision avoidence systems underground.

Add more xbees to act as relays and improve the network, still beats wired solution and getting too close to the collapse. Cheap rf modules don't form network. It will be a b*tch to set up a dozen and manage.