Hello to all,
I have prototyped a project involving random seed numbers for my daughter. I would like to send each random number generated to her android phone/ tablet. The phone / tablet will be no more than 300-400 mm away from the arduino uno at all times during the code execution.A number will be generated every 4 to 5 seconds approx. triggered by a sensor , probably a RS 433 wireless signal at a distance of 20 to 30 meters away from the arduino.

My question is as follows; what is the best solution to connect the arduino to phone/tablet?

My choices are( I think);
1 bluetooth

2 serial cable (ogt)

I have looked at both solutions but cannot seem to figure out which would be the better option.

I have seen a video on you tube where by a usb serial cable is used but that solution also supplies power to the arduino. I will use a separate power supply for the arduino so I don't know how The arduino decides which power supply to use.

My worry about bluetooth is that the signal might suffer interference from the RS433 radio signal from my sensor?
any help would be greatly appreciated.

While the scungiest tablet has OTC, it is not so common on phones. At about $3.50, bluetooth is probably cheaper, and is certainly the most commonly used. I don't think you need worry about interference. Bluetooth is a consumer facility that has to be proof against that sort of thing, or it would be out of business.

If I understand you correctly, your setup is as follows:

Remote sensor --> RS433 --> Uno --> BT/USB --> Android Phone

Is it correct? If so, what do you mean by "send" a random number to the phone? What will the phone do with this number and how will it be read or displayed? I.e. what app, or built-in phone utility?

E.g. I built a weatherstation that sends readings every 5 seconds over BT, that I can then view on my PC or phone via a text-based app like PuTTY (on the PC) or BlueTerm (on the phone). Is this what you mean?

If so, I'd go with BT. An extra component, sure, but it's only a few bucks on eBay, isn't too hard to connect to the Arduino, requires no special programming or library since it uses the standard Serial library, and is basically just a wireless version of USB. Plus, no cables to clutter things up.

Cheers Guys,
I will go with Bluetooth.
My project is still in development . I have a breadboard skeleton built so far but now I want to add an app. for a phone or tablet. I'm currently researching how to go about that. I have looked at MIT app creator and will have to read a lot more.
This project is a random number game but the number must be sent to the phone/tablet by bluetooth. its just for visual purposes and storage to review and compare at a later time.

Habenero you are correct with the "Remote sensor --> RS433 --> Uno --> BT/USB --> Android Phone"

The arduino will generate a random number and send it by bluetooth to her phone /tablet. I've never heard of BlueTerm so i'll have to check it out. that could be the solution to my challenge.

( My son arrived home last year with an ARDUINO UNO for fathers day and set a challenge for me)