Stepper Motor Door Lock

[DanTheMan]

Thanks Jes. I'm starting to grasp it all now. So basically, I need to make sure that this relay is capable of outputting enough voltage to the electric strike switch's input in order for the solenoid (tar for the wiki page!) to do it's thing with the magnet and lock?
Maybe this following question would be answered if I read a bit more into it - but because of this solenoid using the magnetic qualities from the way the wires are coiled and the electricity passing through - am I right to assume that for it to be locked there will need to be a constant flow of electricity through it and for the unlocking part just for the relay to simply stop providing voltage? Or, does the strike mechanism somehow lock into place until unlocked??

I suppose I should give an overall better picture of what I'm trying to achieve here. From a recent project at university I have learnt how to interface various fingerprint readers with my C# code. So I am going to literally fit one of Microsoft's fingerprint readers into the neighbouring wall to the door along side two simple LED's (red and green). The computer will be the otherside of the wall which will compare fingerprint images in order to grant access (green LED lit) or deny (red LED lit). In the case of access granted, lock will be opened. Really simple when it comes down to it - and it's only being used at home so I haven't got as many things to take into account as if it were a commercial solution.

[jes1510]

am I right to assume that for it to be locked there will need to be a constant flow of electricity through it and for the unlocking part just for the relay to simply stop providing voltage? Or, does the strike mechanism somehow lock into place until unlocked??

I believe link I sent about the strike says that it can be configured to either fail secure or fail open. This means that if it is configured to fail secure then when no voltage is applied to the strike then it locks. If it is configured to fail safe then when no voltage is applied the strike unlocks to keep you from getting locked in or out in a power failure.

I suppose I should give an overall better picture of what I'm trying to achieve here. From a recent project at university I have learnt how to interface various fingerprint readers with my C# code. So I am going to literally fit one of Microsoft's fingerprint readers into the neighbouring wall to the door along side two simple LED's (red and green). The computer will be the otherside of the wall which will compare fingerprint images in order to grant access (green LED lit) or deny (red LED lit). In the case of access granted, lock will be opened. Really simple when it comes down to it - and it's only being used at home so I haven't got as many things to take into account as if it were a commercial solution.

That sounds like a really fun project!

[DanTheMan]

Ahh I see what you mean. The thing is, I would want the best of both worlds. Because in the event of a power failure or some sort of electricity cut I wouldn't want to be locked in. But on the other hand, I don't want to be permanently using electricity in order to keep it locked. I suppose it's one or the other.

Once I am in there, I will not be bothered about people coming in and out. It's while I am out of the house that I would like certain things that are kept in this room to be kept secure. So, I could always code it so that it is locked all day (i.e. fail secure as to not use electricity) until my fingerprint is read and then I enter the room. And then, due to the lack of voltage, it is locked again. If anyone wants to come in I just press a button inside. I've still then got the problem of getting out in the event of the electricity cutting out for some reason haven't I. Can the configuration (fail safe/fail secure) be changed without the user knowing (i.e. they don't have to physically change something on the strike switch)??
Thanks Jes, you've been a big help on this so far!

[jes1510]

On that particular model you change the fail mode by loosening two screws on the switch and moving the mechanism. It can't be changed once it's mounted.

I would be safe about it and go with the fail safe mode. You don't want to be locked in a room if the house is on fire or something.

[DanTheMan]

Yer I probably will go for that. And to be honest, it may not even be used permanently but it is a challenge for me to implement this and I am definately goin to complete it. Out of curiosity though, I'd like to know if there is a way around that issue (whether to permanently transmit electricity through it to lock or whether to not but risk being locked in).

[Adrenalynn]

I cheaped out on mine for my lab. I just extended an old servo motor's shaft with a piece of tube and a couple servo hubs, and clamped it around the pin on the deadbolt with the handle removed on the inside. Four more self tapping screws and you're done. And it's 20 seconds to write the code to control it with an SSC32. A day if you wanna make it all wireless - and find a doctor to squirt the RFID tag into you hand.

Stepper motor is way overkill in this application, IMHO. Not shooting for a ton of accuracy or torque (or even speed) here. Mine will throw the lock in a quarter of a second.

Sorry - back is beyond killing me today - being brief.

[Rudolph]

At least one electro-mechanical deadbolt I've seen has a little hatch on it, covering up a 9v battery connector. If the power's out just hold a 9v to it and (on this one) punch in your code to get in, then take the batt with you. The inside of the door part was just a standard twisty knob.

You wouldn't want it to "fail open", otherwise some ne'er-do-well would just have to cut power to the house to waltz in your door (for example)

[Adrenalynn]

I use a good ol' key as an override. That's the nice thing about modifying a lock as I described. Externally the "traditional interface" still works fine.

[ScuD]

You've seen pics of the mess I leave in my shop.

I don't need a lock or security system, people start screaming for their mother at the slightest glance.

Hi-tech protection is overrated!

[jes1510]

I use a good ol' key as an override. That's the nice thing about modifying a lock as I described. Externally the "traditional interface" still works fine.

The strike that I have been describing works the same way since it replaces the keeper in the lock set. If you simply leave the handle unlocked then the door will still open.