So...I new to all this and my first project is a gate warning system for my folks PLEASE HELP!
I've put the details below so have a look and tell me what you think any advice
would be much appreciated!!!
Thanks
George
Gate Warning System
I’ve got a situation where our large steel gates at the end of our drive (700/800m as the crow flies) gets used a lot but what we need is a device to know if that gate is shut or open. And all we need for it is to have a LED light shine red when its shut and green when its open or vice versa and an orange LED light to know if the battery of the transmitter is finished or low. Ideally the battery needs to last a year or to be replaced between 6 to 12 months or we can connect it to a mini solar panel so power is no problem but it depends on how much power the transmitter consumes preferably it needs to be a Low power consumption module and transmitter.
I have come up with a selection of things that may be of use in making such a device. Also I’d like to skip anything that will involve programming as I’m sure there is no need for it, just good old hardboards will do.
There are devices out there that can do the job but cost far too much and do to many things on top of what we would need which will be useless to us and all of the ones we have found cannot reach the distance we require.
So I’m thinking: - Magnetic gate contacts – connected to a module powered by battery or solar w/battery to last a year - connected to transmitter to reach distance of 700/800m – to connect to receiver – then connected to module with LED lights indicating open and shut signal and low battery – then powered by mains. I saw an example on a page somewhere that said: -
mcu>encoder>transmitter>receiver>decoder>mcu
is this close to what it should be like? I guess the main question is can this all be done if so how and if yes how much will it cost. I made a selection based on what I have found on the internet, can you tell me if what I have found is even the right parts to use and if they’re not; what will be; and If you can’t help in making such a device could you find someone that may help us in doing so?
Parts I found to help build it the system.
A. Magnetic strips (to let the transmitter know if the gate is open or shut)
Url:- GE MaxiGap Wide Gap Overhead Door Magnetic Contact
Url:- Sentrol 2505-A Wide Gap Magnetic Contact Kit for Alarms, Industrial Commercial
B. Modules
Dont know what to look for?
C. Battery and solar options for transmitter and module
Found a few but these can be added later.
D. Transmitter receiver (Long distance)
URL:- 2KM Long Range RF Link Kit with Encoder and Decoder
E. Cases (Waterproof casing) for the module and battery for outside.
Again have found a few but not important yet.
First find a radio link that works over that rather long distance and verify reliable performance. This is not easy.
There are some 434 MHz modules advertised as "2KM Long Range RF Link Kit with Encoder and Decoder" (e.g. from SeeedStudio) but they do not work as advertised.
Those are the precise links to which I referred. I am quite certain that you will be disappointed, but I would be delighted if you could prove me wrong!
You can certainly try those modules, but as I said, establishing a reliable radio link over 700-800 meters is not trivial, especially if not line-of-sight. Trees and other vegetation are also a problem. Tell us more about the exact situation.
Lower frequencies (434 MHz) generally have better range that higher frequencies (2.4 GHz), and good antennas (e.g. balanced dipole) on both transmitter and receiver are absolutely required.
Spend plenty of time with Google, reading customers' comments on product pages. High power XBee modules are an option.
Ok cool, sounds like it can be done maybe. But with I little more though than I originally anticipated.
So...the situation is, live on a farm, open space barely any trees (a few but one or two in the line of sight) around the only thing between point A & B is a small hill. folks live downstairs so it best that's where the receiver is but I can put it upstairs but even upstairs I still cant see a line of sight. picture attached. excuse the Photoshop skills.
Id like to avoid programming if possible as it makes a simple thing complicated, but your saying this cant be done reliably without a proper connection? also how much power will it consume? too much for a battery to last a while?
Il put my hands up and say I'm still so lost in this whole thing, I though I knew a bit but clearly don't and honestly now I don't actually know what to connect to what to make these things work - I have on the other hand spent a lot of time sourcing the web for plenty of information and have found a lot of info about boards battery's etc separately and have bookmarked a lot but don't actually know how to put it all together or what I need to put together. but it would be great if you could please point me in the right direction!
Is the "Magnetic gate contacts - connected to a module powered by battery or solar w/battery to last a year - connected to transmitter to reach distance of 700/800m - to connect to receiver - then connected to module with LED lights indicating open and shut signal and low battery - then powered by mains." / ''mcu>encoder>transmitter>receiver>decoder>mcu'' idea still cool? what I don't know how to do is the green/red and battery lighting warning system. Or is that the easy bit. If I put this all in your hands how would you do it?
So we've got the antenna - The XBee sounds like the best option probably the XBee Pro 63mW RPSMA - Series 2B but it includes programming right. what module do I need to connect it to etc? So If I did get the XBee what next?
I did all the reading customers comments on the other products that I showed you along with loads of other stuff but im clearly looking in the wrong place. And have clearly only covered the tip of it. but il look into it more now but if you could tell me what to look for that would be amazing.
That distance should be relatively easy with 433Mhz, especially in a farm environment.
You should be able bridge that distance with a few milliwats and two directional aerials.
I did once (long time ago) 20kM with 10mW.
Power is NOT the answer. Directional aerials is.
Leo..
With the hill in the way, a repeater station at the top is required. You must have line of sight with these high frequencies.
By "directional aerial" Wawa probably means a Yagi beam antenna, probably with 5 or more elements. They are easy to make but the entire project will be nontrivial, and quite a learning experience for a beginner.
Depends on your pocket but I tend to like the idea of a radio control aircraft/car tx/rx .
Gate would operate one joystick via mechanical hook-up.
One could simply operate a servo in the house to close contacts for a couple of LEDs.(or an open-shut mechanical arm)
Low voltage could be in the form of "lost model alarm" unit at the house also.
All cheap and easy to get, simple to set up etc.
Easy to test for range before you actually build anything as well.
Just need a solar panel and battery of the correct size for your Tx end.
Maybe just an inexpensive 12v car battery?
I've run old 27meg radios off them for model boats.
Just had a look and this site says the distance is actually 412m clearly that makes a huge difference? I was way off, but having said that im like the idea of the directional beams but like jremington says - its a big job.
Not quite there yet but maybe the distance change makes it possible now?
Can do the repeater station -that would defo work. think that the game changer that one. like it. So lets say I go with the point to point via repeater, what next?
Or I can just go with bluejets idea? sounds good but is it reliable and can it make it over the hill??
bluejets thinking is what I was kinda after and makes more sense? as all this is just so that when a gate is open the light is green and when its shut its red or vice versa. trying to keep it simple but maybe it cant be done simply? its that hill - why god did you create it there, when the rest of the lands around us are flat.
Id like to do it bluejets way or il happly do it the 2x XBee's and a repeater way - so which one is it?
Il be using a single set of magnetic contacts that are usually made for windows to prevent burglaries and I just need the signal that gives of when its closed or open sent back to the receiver back at the house to give a green or red light signal.
can this be done using bluejets way? or is it defo a 2x XBee/repeater way?
Yea read up on batterylife with rc, not impressed, liking the XBee system more as I can learn/work and attach to and from it, breadboards and all that.
So that said, XBee it is then. The repeater station is this just an xbee set up to repeat?
The monitoring link - as mentioned is awlays a challenge, and the 433MHz ideas are a good starting place. What you want to do is not hard - but may need some eyes on site to figure out the best solution in the circumstances.
If you have cellular coverage - why not two 3G modems - with a permanent data session (no traffic == very low billing charges). Managing the connection is relatively simple, and you don't have to manage the infrastructure.
Bonus - you could set it up if the gate is open for longer than (say) 5 minutes - it sends you a text or email message...
