Ah right awesome, because I will only need one USB-to-serial to program them all! And right thats good as well, I didn't realise those Jee Nodes could each send and receive! They do sound like a good and affordable solution since you can get 6 for $99! But I will have to think about it as it might not be complicated enough for a third year university project :/

The JeeNode is a pretty popular (and cheap device) for building small RF networks with the RFM12B module: http://jeelabs.com/products/jeenode

Ok so does that JeeNode require an Arduino board as well as I am a little confused, or does it work on it's own? I'm just thinking that all the Arduino's are going to have to be able to send and receive meaning they will need a sender and receiver each!

And thanks KirAsh4 for the reply, you network sounds ace and I think I will only be sending data every 2 hours or so anyways!

Right Ok thats understandable and I will try to answer those questions the best I can for both ideas.

The thermometer idea will have the Arduinos placed about 5 meters apart and will be traveling through standard house interior walls. I plan to power them via the mains power sockets so that they get all the juice they need. As for reliability and noise I am not sure. The reliability needs to be fairly good but not to a huge degree, and as for noise I guess just standard house stuff, wifi, microwave, phone etc.

Next is the dot counting idea. This time the Arduino's will be placed very close to each other, like a hand or arms length away. Again they will be powered via the mains and the noise will be the usual stuff. However the reliability needs to be greater as the answer must be correct every time.

Thanks or the Module info, I will take a look at them both!

Well that's my question, is there a cheaper way of doing this? RF modules, bluetooth ect.

So will RF modules be able to achieve these tasks do you believe?

And thanks for the quick reply!

Hiya everybody,

OK so i am currently working on ideas for my final year university major project and I currently have a couple of ideas, however both my ideas involve a lot of cost and I need some help.

Right, so idea 1 is to have 4 Arduino Uno's which are place in 4 rooms throughout the house. Each Arduino has wireless capabilities and a thermometer attached. Every now and again at a set time, Arduino A will read in the rooms temperature and send this data wirelessly to Arduino B. Arduino B will then read in it's room temperature and send this data along with A's data to Arduino C. Then C will sent it's reading to D along with A, B and C's. Finally D will send all the readings to a computer for analysis. Now I know it would normally work where each Arduino would just sen their data direct to the PC but this does not show networking ad-hoc skills like I must for uni.

OK that's idea 1,Idea 2 is to have 3/4 separate compartments with an Arduino sat in each, again with wireless capabilities. I will then place a random amount of black dots in each compartment and hit the "go" button. When started each Arduino will read the amount of dots placed in their compartment and then sent the result to all of the other Arduinos. Each Arduino will then gather all other results, calculate the total amount of dots and display them on a screen.

However as mentioned both ideas require wireless capability. I wanted to achieve this by having 4 Arduinos, 4 wireless xBees and the 4 boards needed to attach the 2. I have worked this out to be about £215 worth of stuff which is way too high. Therefore my questions are these, 1. Are these project ideas stupid? and 2. is there another way of the Arduinos cheaply communicating wirelessly?

Thanks in advance?

Hiya,

OK so I currently have  a breadboard with three push buttons on. They all share the same earth and 5v input but through their own 22Kohm resistor to the ground pin. They then all have their own feed to the Arduino's digital pins so that I can read their state.

My problem is that I have got the program to print the state of two of the buttons to the serial monitor and one of the buttons keeps showing as high every few seconds, then it's fine, then every second etc. The other button is fine and only shows as high when pressed, and when pressed it can cause the other random button to stay high?

Any ideas on why this is, is it because they are all using the same 5v input or ground? Also to mention there are other things using the 5v feed such as a LCD screen, thermometer and LED. Could this be an issue?

Thanks, Sam!

Hey,

Thanks for the quick replies, this has answered my question perfectly. However out of interest, why not stay in an interrupt for ages, does it do damage at all or just not good coding? it is the only way that I could think of at the time to get the Arduino to do what I wanted but with the flag idea I may have just thought of another way.

Thanks!

Hiya,

OK so I am using the attachInterrupt function on the Arduino for the first time today and it is mostly going smoothly. However I have a quick question, if I have a push button attached to interrupt pin 0 (digital pin 2) which when pressed runs a function, if I push that button attached to interrupt pin 0 again during the function being ran by the interrupt, will it interrupt and restart the function?

Sorry if that is not clearly explained! Another way to put it, can you use the button your using to interrupt during the function the interrupt runs?

Haha, thanks in advanced!

Ah yea I get that now. I know lots of people blow things up, and my time had to come at some point, just wanted to know how/what blow but I know now so thanks! And good design there on your part!

  god'am it! Really gutted! I am guessing it wouldn't make a difference if I was to say that it wasn't connected to the serial cable/laptop when it happened? I was connected to an external 12v power source instead.

Anyways it sounds dead forever so that sucks but you learn from these things. How does it break the serial port then? Or is it not east to explain?

Thanks!

Hey everybody!

OK so I was working with my Arduino for my University major project, when, a 12v wire mistakenly touched the 3.3v leg of the thermometer that was attached to the Arduino! The Arduinos lights flashed, the LCD screen flashed, the 240v relay flashed....you get the picture! Anyways now the LCD won't turn on but has a faint light on it, the green ON LED on the Arduino is on, the TX and RX lights are faintly lit and a orange LED is on by an L.

So the sketch is no longer running and my laptop won't recognize the Arduino when plugged in. I have disconnected everything from it but the USB cable and still the same lights lit on the Arduino, PC won't connect to it and the sketch won't run!

Give it to me straight, is it dead or can it be fixed?

So... What type of diode am I using, and where's it going?

Haha! 

Hi everybody,

Thanks for all your replies, they have all been so helpful, especially yours krupski!

As for the snubber diode mentioned by you midon, the diode will be going from the positive connection to the negative connection on my fan, correct? I have scanned through that wiki link you posted but I am a bit useless at learning from large blocks of text! Can you recommend a specific diode for this job?

Thanks again, Sam!

Hey everybody!

OK so I am looking for a transistor capable of running a 12v 0.10a fan from an external power source, powered by the Arduino. I have a mixture of transistors but don't know if any are able to cope with the 12v/0.10a being carried through them. I have looked up the datasheets for a few of them but do not understand which bit it is that I am suppose to be checking, e.g. Collector-Emitter Voltage, Collector-Base Voltage or Emitter-Base Voltage?

Any help would be greatly appreciated, thanks!

Sam!

Thanks you both so much, I'm useless at gaining information from such little writing! I will certainly try that length wire when I get the chance and also 1000 baud as well since I thought you had to go up in doubles starting at 300, eg. 300, 600, 1200, 2400 etc

Thanks so much!