passive/active RF for door lock/unlock (schematics? urls?)

[kiko187]

I was thinking of putting an electric deadbolt in my home entrance, then thought why not have a remote for it?

But when I get to thinking I tend to go for the extreme...

I will have a power source for the door lock (which can be suplimented with a battery backup) therefore I will have enough juice to run a RF sensor.
I know that if I had to have a RF transmitter I would have to either push a button or run thru batteries with always-on.

Now, to my question, I want to make a passive / active reciver/transmitter so that when I walk up to my door it senses the reciever (keychain in pocket) and unlocks.

I know that if I had to have a RF transmitter I would have to either push a button or run thru batteries with always-on.

which is why I want the keychain to be passive, and non batteried.

Or is this too much to ask for ideas, for?

 

[kumbanadan]

 

[bmcculla]

RFID is designed for RF identification. It doesn't require a power supply in the transmitter It is powered by the RF field broadcast by the reader. It sounds like what you are looking for. I'm not sure what the effective range is though.

Hope this gets you started

Brent

 

[kiko187]

that is definetly the right direction...

its almost like the anti-theft post, only in this case when you get close to the sensor it unlocks a door!!

(now to find the hardware to do this without going broke!!)

 

[Spex]

You'll have to be careful that you're not doing a lot of expensive wheel re-inventing here - or perhaps you don't care and are just doing this for the fun of it which is also fine.

There are a lot of RFID products on the market, you can google for the manufacturers. The power for the ID device comes from the reader, there are a couple of different standards but the most common one works at 125kHz or thereabouts. Have a look for HITAG 1 and HITAG 2, TEMIC, MIFARE, these are all available technologies for ID devices and readers.

If you have "limitless power" ie you make your reader mains powered then you can transmit all the time and wait until an ID device comes into range. Alternatively you can use some sort of proximity detection device to see when something moves close to the reader and only then start reading. Short range passive infra red detectors are being used for this in some products on the market.

On your house you are probably going to install a "fail secure" electric lock of some kind so that your house isn't open if there's a power outage. So you do need to still have your old key or something similar to let you in under these circumstances....or of course if the electronics fails you still need to get in, but hey, that'll NEVER happen.... :wink:

Really, there are a million products on the market that do what you're looking at doing and they cost next to nothing so if you're doing this as a hobby project then fine but if you're doing it for more commercial reasons then I'd do a little research first before you spend any time or money.

 

[kiko187]

"the wheel" ? hmmmm, lets see if we can get it made from a few of these circut boards I have laying around here... :wink:

thanks for the heads up. if you happen to spot a reasonible price retailed solution feel free to post it, I havent found anything that was in the range of non-institutional use. :cry:

 

[Spex]

Well dealing purely in the old Euro (cos that's where I am) you need a reader/controller, a lock and a power supply.

For domestic I would recommend a fairly decent lock which is the most expensive part of the whole thing at around Euro100 (you can get a lot cheaper but you get what you pay for with electric locks).

The reader/controller together would cost a further Euro100 and the power supply is just a transformer so <Euro10.

The RFID fobs are about Euro5 each in small quantities.

So altogether you're talking about Euro220 or there abouts. At today's rate that's around USD275.

The benefits of electronic access control come into their own when you have a large number of doors or a large number of users. In these circumstances access control provides a much neater way to manage the situation than do traditional lock and key.

In domestic applications where there are few doors and a well defined small group of users the best solution is still lock and key and will probably remain so for some time.

When I say "best" I'm talking about the cost/benefit "best". The use of "a more hi-tech" solution in this environment doesn't really stand up all that well to the higher cost and reduced reliability of the electronic system over the good old fashioned lock and key (electronic access control is not un-reliable, however it is less reliable in these applications than lock and key because of the multiple possible points of failure in the system).

As you can probablt guess, I work in the access control field and have done for quite some considerable time.