Wireless suggestion please?

[krypton_john]

Hi All,

I need to place a keypad outside our automatic gates to allow remote opening. However the keypad will need to be on the opposite side from the power and the gate control box and I don't want to dig up a trench to lay more wires.

I could easil make a keypad and simple picaxe circuit but will need a wireless sender and reciever for the gate controller.

Also, I'd like to design it so the batteries will last for months if not years, so it should power on with the first key press, and power off after sending it's message.

The transmit distance will only be a few meters. However it might also be handy to send a message 30m to the house to activate a beeper.

So, what would be a good wireless module for this purpose?

Thanks very much,
JohnO

EDIT: Gah, didn't search very well before posting. Great answer here: http://www.picaxeforum.co.uk/showthread.php?t=14912

 

[manuka]

Glad you searched past postings! Given the modest distance I'd say IR may well be worth while too. Significant issues may well be weather proofing,fail safe needs & prevention of false triggering, so before you go mad on total DIY I'd suggest you check products on the market. Bunnings, Warehouse & Jaycar etc have all manner of offerings, & many suit PICAXEing.

 

[hippy]

It's probably going to be a bigger task designing the PICAXE and keypad circuit to use zero power and turn on when the keypad is activated than choosing a wireless module.

If you can't achieve the battery life you want it will have to be wired and if it is then wireless isn't needed, so the critical path is getting that working. Using rechargeables and solar power may be one solution.

A tip for outdoor keypad code numbers - make today's date part of the code; that way, after a few months of use, there's less chance of four shiny buttons with the rest covered in crud which partly gives away the code number

 

[clockwork]

The idea about the date is a good one. However if you dont want to go to all the trouble having a functioning clock and comparing the imputted date information then Instruct callers to imput the date using 6 figures but have the software ignore the first 6 figures punched in.
This will still keep all the number keys nice and clean. Most will never figure out that the first 6 numbers can be anything they chose.

Using a rechargable battery and solar panel should be fairly easy to impliment as a picaxe plus low powered radio transmitter module will not take that much current and unless you have thousands of visitors should easily be able to keep the battery voltage up.

 

[krypton_john]

Thanks very much for the comments guys.

1) Power on/off - I'm pretty sure this has been covered here in the past - if I have to roll this myself it sure will be the trickiest part but also interesting
2) Matrix keyboard decoding - been there, done that
3) Waterproofing - Futurelec have a $6 waterproof keyboard.
4) IR - possibly, but issues with LOS. alignment etc?
5) Dirty keys - interesting. I've never noticed this anywhere else being an issue where keypads are used though.

Once again, thanks for all the good comments. Plenty to think about.
JohnO

 

[papaof2]

5) Dirty keys - interesting. I've never noticed this anywhere else being an issue where keypads are used though.

But you're not the miscreant looking for way in ;-)

The mechanical push button door locks show the usage pattern in a ear or so, depending on number of uses each day. Indoor keypads are less likelt to show this as the forces invoved are lower. An outdoor keypad will get rain, dust, whatever spattered on it unless it is in a weather resistant enclosure. The used keys will definitely be cleaner than the others.

John

 

[hippy]

5) Dirty keys - interesting. I've never noticed this anywhere else being an issue where keypads are used though.

You've not looked closely enough

Even indoor keypads get grubby, but mainly the ones pressed ( rather than not pressed - oily, greasy fingers ! ) and especially if plastic membrane covered. Worse, those end up with slight depressions on keys used regularly.

It's even possible to feel which keys have 'more give' or don't sit as flush or as square as the others.

Plenty to think about.

Plus an opportunity to think of an easier way to do things. Such as forget the keypad on a stalk and just issue everyone with their own wireless key fob remote. Don't even have to stick your arm out in the rain then

 

[krypton_john]

I think for the purposes of this project the keys getting dirty is not a big deal. If someone really wants in they can just jump over the fence in less time than it would take to try all combinations of the 'clean' keys. And inside the gate there is a plain push button to get out. It's not Fort Knox.

Fobs are no good as there's too many people I'd want to have one - in-laws, friends, the cleaners, meter reader etc (ok, not the in-laws!). Fobs get misplaced, cost money etc. I can make this project up out of parts I already have in my picaxe junk box plus a $6 keypad and $5 RF modules.

This gate is mainly to keep toddlers and pets in and Jehovah's Witnesses out. It is a disincentive to drive-by casual burglars at best.

 

[Janne]

Put the keypad outside, but strip the components from the inside. Replace with a reed relay, that will supply power to the picaxe, with some sort of software latch circuit. The axe then sends the "open sesame" code wirelessly, and shuts down.

Good thing is, that no-one will spot from the keys what the code might be And no-one will gues that the gate will open with a magnet.