Simple Wireless TX to switch Device On or Off,

Wireless & IoT
1

I’ve searched this and other forums and am having a mare of a time solving what on the outset I thought was a simple enough problem.

A friend came to me as I’ve worked with Arduino, and it seemed ideal for this project, the more I work on it, the more I doubt that.

The situation is simple enough, Chinese made long distance 433 RX/TX switch not performing as hoped, i.e., Not working.

I thought it would be as simple as getting an Uno, plugging in a 433RX module, picking up the signal from the present TX and doing the business with a Mosfet.

The issue is the 433TX Signal is rubbish, inconsistent, if or when I do pick it up, it rarely repeats an identical signal so It is difficult to get the Arduino/RX setup to perform an action based on the signal received, when it receives it.

So my plan is to scrap the 433TX and just make a new system from scratch.

The goal is this;

From 500m (550yds) away, turn on a device for 45mins. (A solar powered warning sign).

Progress so far, Arduino powering the mosfet for the time period on receipt of a serial command. So instead of the serial command, I want a wireless command of some description.

It looks like Xbee is going to be the way to go, but it seems like absolute insane overkill for what is basically going to be sending either a 0 or a 1.

Not to mention series one or 2 etc…

Perhaps with the right aerial a 1 or 2mW tx will acheive the goal?

Any help is appreciated.

Thanks.

2

550 yards… 433MHz in the US, w/FCC regulatory constraints, $3 radio. Not doable.

for that range, you’ll need something like 100mW in the 902-928MHz band. Costly - like $75 per radio.

Or if one end is fixed and can use a high gain antenna, and there’s reasonable line of sight, there are other options.

Can you describe the physical conditions?

Are you in the US/FCC regulatory region?

3

Hi, thanks for your speedy reply.

The RX is fixed, to a street sign, so a larger antenna is doable.

Im working with 550yds line of sight as a worst case scenario, realistically it will be a couple of hundred meters but from inside a building, mostly from somewhere that the sign is visible.

Im based in NZ not the USA, our regs are a little more lax, ie 433mhz band is unrestricted!

but that said, it is being used around small children.

4

If it will work and achieve the goals i can spend what is needed, we were quoted $1500 by local company Tait to achieve this! Less is probably better though…

5

So if you can spend what is needed, then what’s the problem with Arduino and XBee? It’s not overkill. Overkill would be spending hundreds of hours of engineering time so you can build a one-off device for $5.

cpjfox:
If it will work and achieve the goals i can spend what is needed.

6

Hi Lyndon,

The statement of over kill wasn’t in relation to the xbee price, i am wary as I’ve never used that form of communication technology, and in the series 2 descriptions spark fun goes to the trouble of warning how complicated the setup is.

Id really need someone to hold my hand (figuratively speaking) for the setup.

Or at least advise on the best xbee componets to be my tx and rx, im even confused as to which is which, or is each model both an rx&tx?

And do both ends need arduino? Does either end need it? Given the requirements above… Which ever unit would need external antenna ability as both will be mounted in weather propf casings.

7

I haven’t used the XBee, but a friend whose judgement I trust assures me that they are pretty simple. Their most common usage seems to be as wireless serial cable replacements, so simply replacing the cable you’re using to your Arduino right now with two of the devices should be all you need.

I have used a few different Bluetooth devices and they are trivial to use. But the Class 1 Bluetooth spec is only 100m, longer distances are possible but nonstandard. I’ve a couple of the 433MHz devices, but I haven’t gotten around to using them yet.

8

XBees are simple if one takes a little time to read and understand.

They are not as simple as an Ethernet cable.

Too often, novices buy a $4 on-off-keying transmitter or receiver and then, after hours of struggles, realize why IEEE 802.15.4 and products like XBee make it easy. Compared to reinventing the wireless modulation method, error detection and correction, node addressing, and the like.