Hi there, i am starting a new project here, where i want to make a wireless petrol pump. so i have done the hardware part till the pump works by using arduino mega. now, i want to add features so that i can change the petrol price (changing the coding) wirelessly without me having to reconnect my arduino to pc and reupload the programming. is there any way for me to do it? maybe by using wifi shield or something?
thanks for your cooperation. 
How much range do you need? The NRF24L01+PA+LNA seem to have ~100 feet range(you might want to research this better).
This one super long link claims to have 1000 meter range. Probably not that good, but will have some range.
fahmijaafar:
Hi there, i am starting a new project here, where i want to make a wireless petrol pump.
You mean a pump at a service station (gas station?) I'm not sure exactly what kind of petrol pump you have.
fahmijaafar:
so i have done the hardware part till the pump works by using arduino mega. now, i want to add features so that i can change the petrol price (changing the coding) wirelessly without me having to reconnect my arduino to pc and reupload the programming.
OK, this is a reasonable request.
The clue is "without re-uploading". You want to save a price variable on the Arduino which doesn't change when the power goes out or for any other reason until you request it.
Use the EEPROM memory. It's very easy to save a value in the EEPROM and it stays 'forever'.
fahmijaafar:
is there any way for me to do it? maybe by using wifi shield or something?
So you don't currently have communications with the Arduino outside of the programming cable? Woluld a wired solution also work for you?
Bluetooth should be the easiest as it appears to the Arduino just like a serial connection. Serial input basics may be useful.
If you could upload the price from an Android phone this RemoteXY Thread may be of interest.
When the Arduino receives a new price it should, as @MorganS has said, save it in the Arduino's EEPROM.
...R
i was thinking of monitoring the petrol pump from a far distance. basically, using internet connection where i can monitor and change these values:
sounds like you need to just add cell phone number and or have local internet wifi.
if you have available wifi, you can connect to the internet.
if you do not, you can make the unit a cell phone and then have it call out daily with reports or you can call in an change price.
here in the States, we are only allowed to change price 1 time in a day or unless the truck comes with more.
if your fueling depot has internet, you can add security cameras as well as monitor pump operation and also tank level.
it would seem that you would already have that so you can collect the money.
please describe every type of connection you have. if you have a phone and internet, wifi or whatever.
If you don't need internet, you can use XBees in transparent mode. One connected to a computer with a USB XBee Explorer, and the other connected to the Arduino with a XBee shield. Be warned, the XBees are 3.3V devices and not all shields have level shifting.
Then, you can use some software on your computer to communicate over the wireless link. It is just like using a COM port- the Explorer has a FTDI chip in it.
Make sure you get Series 1 Xbees - they are the easiest to use and the cheapest.
An Arduino Yun has WiFi built in and AFAIK you can also connect a 3G/4G dongle to one of them.
...R
Robin2:
An Arduino Yun has WiFi built in and AFAIK you can also connect a 3G/4G dongle to one of them....R
so, now im using arduino mega as the controller. would i be able to:
wirelessly using Arduino Yun? by wirelessly i mean wireless LAN n not bluetooth
thanks
fahmijaafar:
wirelessly using Arduino Yun? by wirelessly i mean wireless LAN n not bluetooth
If you mean that you would replace the Mega with the Arduino I think the answer will be YES. The only doubt is whether you are already using Mega features that the Yun does not have.
If you mean install the Yun alongside the Mega (and connected to the Mega so it can treansfer data) the answer should be YES - but obviously not cheap.
If you mean using the Yun to send data wirelessly to the Mega there would be no advantage using a Yun rather than a smartphone of PC. You would still have the problem (and cost) of adding a WiFi receiver to the Mega. It may be worth considering an ESP8266 wifi module - they seem to be cheap.
The advantage of the Yun is that you can program the Linux side with Python.
...R
fahmijaafar, please detail how you connect to the internet.
if you have a local wired internet connection, near the pump, you can just hard wire the controllers.
if you have wifi near the pump, you can use a wifi.
if you have nothing near the pump, your choices something else.
the more information you can give means the better solution
hi all, sorry for late reply. so now ill explain my project.
i have done the pump part using arduino mega where i control the ultrasonic sensor, rfid tag and the pump(by uploading coding into arduino using usb connection from pc). basically, the pump is now working fine as i can purchase petrol from the screen and the pump will operate.
now, i'm thinking of improving this pump where i want to control( as a seller) the pump from afar. i have this petrol pump connected to the internet using wifi from like say my phone hotspot, then i control it from a pc using VB interface in which i can
-set its price
-monitor sales
-emergency stop
so here is my question.
which arduino connect me with internet wirelessly?
can it let me monitor live sales?
can i use change EEPROM memory wirelessly using that arduino?
hope i make this explanation clear. thanks for your guides.
fahmijaafar:
i have this petrol pump connected to the internet using wifi from like say my phone hotspot, then i control it from a pc using VB interface in which i can...SNIP...
so here is my question.
which arduino connect me with internet wirelessly?
can it let me monitor live sales?
can i use change EEPROM memory wirelessly using that arduino?
I'm afraid I am confused.
If the pump is already connected to the internet using WiFi I don't understand what the "other" Arduino would be intended for.
If you are thinking of something to take the place of your PC I suggest you consider using your smart phone rather than an Arduino.
Rather than use something like VB (which is limited to the PC the app is running on) I have written a few PC apps which use a browser for the GUI and then my phone can access the same GUI without any extra programming. The PC app is a small web server.
...R
Robin2:
I'm afraid I am confused.If the pump is already connected to the internet using WiFi I don't understand what the "other" Arduino would be intended for.
If you are thinking of something to take the place of your PC I suggest you consider using your smart phone rather than an Arduino.
Rather than use something like VB (which is limited to the PC the app is running on) I have written a few PC apps which use a browser for the GUI and then my phone can access the same GUI without any extra programming. The PC app is a small web server.
...R
i'm sorry. that was a typo. it should reads 'i want to have' instead of 'i have' 
i need to make sure this another arduino whether its WiFi Shield, or maybe even only Xbee wifi module can be used to enable me to make changes like stated above.
after all. i have decided to save the price in EEPROM. then to make change to that value wirelessly, what kind of means should i use? and also to set the relay on/off. before this, i use button and it will on/off and now i want to make it wirelessly. thanks for enlighten me.
