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We have a private car park protected by a gate and our users can open the gate using hand held remotes (we are currently using the Jane ones). There are 24 parking spaces and we have about 50 users, but we sometime have a problem whereby users abscond taking their remotes with them and then use the car park when they should not. The radio receiver and control board for the gate are obsolete and starting to give us trouble: we need to replace them. We would like to replace them with a system whereby we can authorise the remotes individually and then de-authorise them when any of our users leaves the scheme. We have looked at GSM systems but don't like the idea of users being able to open the gate when they are not within sight of it, so we would rather stay with the 433MHz system (or perhaps Bluetooth?).
Are there any systems available which would allow us to authorise remotes on an individual basis?
Thanks - David.
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19-07-2015, 02:51 PM
(This post was last modified: 19-07-2015, 03:10 PM by thm.)
If you combine the output of a GSM controller with that of a set of safety photocells installed as a presence sensor (the cheap and easy option but without differentiation between vehicles and other objects like persons or animals), opening of the gate without the presence of a vehicle becomes quite improbable. An even better sensor for detecting vehicles would be a loop detector but it is more costly in terms of material and installation and may not be applicable in your case.
Optimally, the control board of your gate operator should support an 'open only' button command (to come from the combined output of the GSM controller and presence sensor) and automatic closing and have safety photocells and all other required safety features (safety edges, force limiting) installed and configured. Ideally, the board should support preflashing, so that a flashing light connected to it starts flashing a few seconds before the gate starts moving (important especially before the closing movement). You could also connect a buzzer along with the flashing light so you have both visual and audible movement warning. You can also install a free-exit sensor (in the simplest form, it could be another set of safety photocells installed as a presence sensor and connected as an open-only button command, provided no outsider can jump a fence and get on the inside). You should provide a way for a person that gets locked inside the car park to exit (an alternative exit for pedestrians or perhaps a keypad or a keyswitch) and, as additional safety, a way to contact some manager.
BTW, programmable receivers that support activation/deactivation of remotes tend to be difficult to manage (you usually have to keep a list that tells you in which memory-slot is each remote stored and then you can empty that slot thus deactivating the remote, then you have to reactivate it and assign it to the same or a different slot which you must also record etc - this is usually achieved with a very primitive interface and in practice, takes very strict bookkeeping and more than a pinch of effort). Medium or long distance RFID controllers are also an option but the cost and complexity of most systems don't make them very attractive for small installations. Bluetooth controllers usually operate either as 'virtual keypads' with a common PIN for all users (not what you want) or as a presence sensor that activates when registered cell phones bond with it (which may be what you want but typically has the same managing problems as a programmable RF receiver - for example, one of the standalone devices I know of, only supports 10 cell phones).
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Thanks thm for your helpful reply - there's plenty of food for thought in there.
We already have a buried loop and photocells to detect a vehicle in the closing arc, but I am not convinced they would pick up, say, a child every time. Nor do I think we could change things to be absolutely sure of doing so. There is another potential problem with GSM: someone who is not authorised to use the car park could arrive at the gate, phone a friend who is authorised and who could let them in from pretty well anywhere in the world. In fact, said friend could let in several unauthorised people. I think I would prefer to stay with a line of sight solution.
I take your point about the administration overhead, but that would be much the same with a GSM solution. I think if we went down the road of authorised users we would have to live with that.
After doing more research I have found the Prastel M1000E receiver which would seem to do what we want. It is quite expensive at about £263 + VAT - but it is a one-off expense. Does anyone know if it can be sourced any cheaper or if there are cheaper units that do much the same job? Also, I don't know if it is compatible with the remotes we are using (Jane). I would want to avoid having to change them all if we can.
David.
