Electronic fence lock actuator

I've got a wooden picket fence with a gate that backs up to a park. Sometimes I leave by the street and want to come back through the park and vice versa. But the padlock can only be placed on the inside of the latch and can't be accessed from the other side. If I leave that way I have to leave it unlocked, if I left from the street there's no way to unlock the fence from the outside. Modifying it to put the padlock on the outside would only make it impossible to leave from the inside.

So my idea is to make an electronic lock. Probably a keypad on each side or maybe even an RF tag. It must be solar powered (with a battery of course). The electronics part is no problem at all for me.

The question is, what kind of actuating mechanism can lock and unlock the gate? Ideally, it should be able to stay in the unlocked position with no power being expended because some days I go in and out a lot and don't want to mess with the keypad (a special code would do this). But also, it ideally shouldn't be easily defeated from the inside. i.e. if somebody jumps in over the fence and starts coming out hauling my stereo I'd prefer the gate not be openable just by pushing a locking cylinder out of the way with your fingers. I'm sure if he brings a screwdriver or a big pair of boots he'd get it open but why not make it harder for him?

Also, of course this is an outdoor application and will have to deal with sunlight, rain, etc.

I have a motor-driven car door lock actuator from surplus that looks kinda sweet. It doesn't have limit switches to disable the motor current though, so it can always be easily pushed out of position from the inside.

Actually the whole thing is pretty hard to figure out. If you look at a gate latch with a lever that runs front-to-back (thus accessible from either side) the horizontal bar it grabs onto is mounted on the outside, on the swinging door. On the part that mounts on the fencepost there's a hole in the moving lever that, when closed, lines up with a hole on a fixed piece for padlocking. I was thinking about pushing a bar through that. However, if the gate is open when that happens the bar will only succeed in locking the latch closed but then the gate can't be closed into the latch. It could also push in when the lever's being held up, which would probably lock the lever open and then the door will close but not latch.

Now keep in mind that a wooden fence gate expands and contracts with the weather which is why these broad latches are used for fences. The gate's mating surfaces moves 1/4" up,down,left, right all the time. A stock deadbolt-type door keypad will not line up consistently.

Any ideas on this one? Also, anybody got a line on fully weatherproof outdoor keypads?

I did look at some power latches for hatchback minivans (Dodge Caravan) on eBay. Not too bad an idea even though it doesn't meet all the requirements. I could replace the exiting latch completely. If I wanted to leave it in "unlocked" mode I could just push a button to make it pop open and that's basically no more difficult than pushing the existing lever anyways.

But the door does swing outward, and you really want that horizontal grab bar on the door not the post. Otherwise you may not see it and get jabbed. Thus it would seem to necessitate putting such a mech on the outside where it would get abused/stolen. Or it would have to somewhat inset into the post and I'm not sure there's room to do anything like this.

Have you looked at latching solenoids? They only require power for a few milliseconds each time they are actuated.

Oznog said:

Also, anybody got a line on fully weatherproof outdoor keypads?

Click to expand...

You can get some made by Storm Interface from Allied Electronics. They're not cheap though ... ($65 US).
**broken link removed**
JB

I found a nifty little programmable keypad to replace one on my home burglar alarm which was no longer manfactured. It is made by International Electronics Inc and is a Model 212 i/w.
It runs off 12-24 volts can have up to 120 programed codes and the best part is that it has a high current relay that can drive a solenoid. I think it is primarily used in solenoid operated security door applications. The relay operation can be programmed for a variable operation time of from 1 second pulsed to fully latched operation.
I purchased it at a local security firm, and it was very expensive $125, but it is just what I needed for my application.
Dialtone