I've done some googling on this, not come up with anything that fits well and heaps that's nothing like what I want. I'm looking for a simple wireless controlled switch (relay or something that can drive one) output. Range needs to be somewhat greater than one usually gets with garage doors and the like (50 metres or so). Up to 200 metres line of sight required, for switching reticulation valves.
The transmitter would be a handheld device, battery powered.
The receiver would be a fixed installation, AC power available.
Licencing would be a problem.
Small quanity iinvolved, so cost not a big consideration.
Are you open to getting your soldering iron out, or are you looking for commercial devices only?
In the case of the latter, here's a stupidly over-complicated and time consuming approch that might get around all your problems without having to design the electronics:
Use cheap wireless routers with OpenWrt Firmware installed (basically Linux for routers if you haven't heard of it) and relays hooked up to one of the GPIOs (eg. an LED on the front). Then battle with scripts for a day or two until you can control the relays from a mobile phone (from a custom webpage, or commands sent as Emails to a local Email server on the router network etc.).
To get enough power, you'd have to use a transistor on the router GPIO to switch the relay.
With good routers (power outputs vary, FCC data is a good way to compare) and external antennas, 200m should be achievable. If you have a few of these near each other, the range of the individual routers would combine, so you might not even need that much transmitting power on each if they are a shorter distance apart from each other.
As I said it's all a bit crazy and I can't see myself doing it, but then desperation can do strange things to people, and it does seem to cover all the demands you mentioned (depending on what you meant by "simple") - with a nice big WiFi network thrown in as well.
I think there are commercial WiFi controlled mains switches too, but extending the range might be trickier.
I don't know much about these Smart Phones, but if you can run an ssh terminal on one, it should be possible to connect to a router as a terminal and manually issue the on or off command. You could set up a script or a Linux "alias" so that you just have to type something like "on 1" to control each valve.
If you had multiple routers on the same network, you could put some simple scripts on the "master" one that you ssh into, which then sends commands via ssh to the other routers.
For example if you have one master and one slave router each controlling two relays, and you want to switch the second relay of the slave router, the system could work as follows:
*Phone (or any portable WiFi terminal) logs in to the master router via ssh and issues the command "off 4".
*This executes a script on the master router which tells it to ssh into the slave router and issue the command "off 2" before loging out.
*As is the master router, the slave router is configured such that the command "off 2" turns off its second relay output.
Now if the terminal was a PC running Windows or Linux, it would be easy to make a script to issue commands to the main router in a more user-friendly way than manually loging in and typing each command. I don't know if you can do that sort of thing with a phone though.
Though you could always use a raspberryPi, or even a small router PCB, with some buttons conencted to its GPIOs, a Lithium battery and a script to issue the commands when the relevent button is pressed. Maybe some LEDs to show the status too.
The only advantage of using an Email or web server to handle the commands would be that nothing new would have to be present on a Smart Phone in order for it to work. But in achieving this, the complexity of the scripting would increase significantly.
On the networking front, it should all work in a standard infrastructure wireless network configuration, with connection to the internet optional.
Here's a page showing the commands to control GPIOs on a router with OpenWrt:
Oatley Electronics have some remote control modules and kits, such as the K180B that they claim a range of 200 metres for. They certainly have a range over 50 meters, and it could be 200 meters if relatively unobstructed. The transmitter and receiver modules used, TX9 and RX9, are available separately if you want to cook up your own switching circuit.
They also have a "range extender", TX01, that they claim gives a 1.5km range, but I have never used that.
They seem to work quite well, but there is one thing to take note of: Oatley claim that the TX9/RX9 are "code hopping" devices, but that is not actually true. Each transmitter appears to have a unique serial number that is included in the transmission, however the code sent when a particular button is pressed never changes. For your application, this probably does not matter. Oatley sell other transmitters and receivers that they also describe as code hopping, but I have no idea if any of those are actually what they say or not.
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