Project for local OSH meetup

My local Open Source Hardware meetup group meets on the second floor of a small brick office building downtown, probably vintage 1920's. For security reasons, the front door of the building must remain locked after hours, so as members arrive, someone has to walk to the opposite end of the building, then down one long flight of stairs, to open the door for them.

But that person doesn't have to do anything but walk into the lobby to release the door lock - apparently it's a proximity or motion sensor, which also works to let people out. So, we were thinking if we could communicate remotely with a device left in the lobby, and perhaps make it turn on a fan or something similar, we could let people in that way.

Ok, I just told you all I know about RF. But the problem is this is an old brick and steel building, and the lobby is pretty effectively shielded just from the construction involved, except that it has exterior windows. So the RF from the second floor would have to go through a window to the outside, then come back into the lobby from the outside. Not exactly a straight line.

I was thinking of using 433 MHz transmitter and receiver modules and something like an arduino. The logic would be really simple. The receiver in the lobby would just wait for some appropriate code at 433 MHz, then turn something on that triggers the motion detector for a few seconds, then go back into waiting mode. One-way communication.

My thinking is that the lower the frequency, the better chance the RF has of turning corners, and 433 MHz might be a good choice for cost and antenna length. Does that sound reasonable, or is there a better choice? From what I can tell, the 433 modules seem to be a pretty popular choice among arduino guys for radio control projects.

Anyway, comments and suggestions would be appreciated.

By the way, the irony is not lost on me that this would be an OSH project for the OSH meetup group attempting the solve the problem - how do I get to the freaking OSH meeting. But that's ok - this project is appropriate for my level of expertise.

Reply to
Peabody
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I posted a picture of the building in the alt.binaries.schematics.electronic newsgroup.

Reply to
Peabody
[...]

I ran into this problem with a local gym. Fire regulations say you cannot prop a door open. They needed to allow newcomers into the gym to show them what benefits the could give them, but the existing lock wouldn't let them do that.

If you can change the lock, there is a special lock for schools to protect the children against attack. I don't remember the name, or the search string I used to find it. But it only cost $50.00 or so, and I got it at half price since it hat been knocking about in the back of a pickup and the original box was a bit dirty.

As far as I can recollect, it was a normal key entry door lock. But you could bypass the lock from the inside so anyone on the outside could turn the knob and open it without any hindrance, just like any door without a lock.

After the meeting was over, all you had to do was to insert the key and lock the door. Now you could exit from the inside if needed, but nobody outside could enter. This was ideal to secure classrooms from people with guns since all the teacher needed to do was unlock the door before class, then lock it after everyone had entered. Those inside could get out, but nobody outside could get in.

There was only one locksmith in town who had this kind of lock, so it might take a bit of searching to find it. But it could save you a lot of problems during your meetings.

Reply to
Steve Wilson

Get a cheap wireless doorbell and see if it works. If it does, have the receiver make some heat to wake up the motion sensor.

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Reply to
John Larkin

What would the Arduino do? You push a button and a signal is sent, so what's the need for software?

Reply to
Tom Del Rosso

Honestly, I don't know. All the examples I've found so far on Youtube use Arduinos at both ends, and they require software libraries to handle the communications. I haven't found any detail on how the transmitter's data pin is driven, or what comes out of the receiver module's data pin. It appears to me that most of the Arduino stuff tries to protect the user from having to know anything beyond which library to install. Most of the time that's fine, but sometimes it would be nice to know more. But I'm still looking for that information.

I think some kind of logic is needed to make sure that what's received is coming from my transmitter, and isn't some other transmission, or just noise. So a code of some kind would need to be sent just to have basic authentication and security. And at the receiver end, I would need some logic to turn on whatever device will trigger the motion sensor.

Reply to
Peabody

Well, the $20 remote doorbells don't seem to have false triggers. Something with more range shouldn't either. Maybe your Arduino Maker group should ask a ARRL group how to do it. :)

My friend is a communications consultant and has a lot of old dishes and other gear. When the broadcast engineers went on strike their union came to him to rent some gear for a couple of days. They tuned it to a different frequency and pointed the dish up at the news copter to jam their signal.

Reply to
Tom Del Rosso

Ok, I found something that might work, and while it says it's for Arduino, we wouldn't need any additional logic at either end:

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It's 315 MHz, and has built-in authentication logic that should take care of the noise issue. It has four channels, and of course we only need one, but I doubt a single channel version would be any cheaper.

I have no idea whether the RF will reach far enough, but at the price it makes sense to give it a try.

Reply to
Peabody

There are many dedicated encoder-decoder pair of ICs used in simple remote control systems. They are easy to set up but quite effective. An example is the Holtek HT12E (encoder) and HT12D (decoder). They have an 8-bit security code that can be programmed with jumpers or DIP switches. No software needed. They are also widely available already kitted with 433 and 315 MHz Tx-Rx paired modules.

Reply to
Pimpom

Don't want to be a nay sayer but, aren't you defeating the security if your not having an actual person at the door to verify who is entering?

Mikek

Reply to
amdx

Sorta like sticking a chair in the door?

Reply to
krw

The unlock would be triggered only after the group member has called on his cell phone from the front door.

Reply to
Peabody

ITTT.com

you're in a city right?

GPRS

you're over-thinking it.

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Reply to
Jasen Betts

Thanks for your comments. But I may be underthinking it. Are you saying I should dedicate a cell phone to this?

Reply to
Peabody

yeah, you'll need to dedicate a cell phone account to this purpose while it's in operation. that means being without phone for a few hours or getting a cheap account.

Unless you can use wifi.... maybe there's an open network nearby, that's reachable from both locations, even a cafe lan with a click-thru to access the internet would work, you can do lan traffic without the click-thru, you won't be able to use ITTT without internet, but it's not really needed, it's just a simplification.

power-line ethernet is another possibility, but doesn't often work well between floors in commercial buildings

If you've got cold telephone circuits in that building that go where you want and can have one dedicated to carrying a signal from your office to the lobby that may be an option, or maybe it can go direct to the control panel for the door lock.

One office I was in had a pair in the phone routing panel that would unlock the door, I found some unused circuits that went to another panel beside the door, and a convenient hole in the concrete slab wall and we installed our own PC based RFID system (which we had already develped for a different purpose) in parallel with the landlord's.

I'm guessing that pair, and the hole, was for a "doorphone" intercom used by a previous tennant.

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Reply to
Jasen Betts

On a sunny day (7 Oct 2017 01:19:32 GMT) it happened Jasen Betts wrote in :

There are many ways... for the boat I have a Raspberry Pi with a Vodafone Huawei USB stick (has SIM card of course). It will dial me when water comes in, when it leaves position (anchor alarm), other mishaps, and report the whole system status, temperature, CO, humidity, etc.. All SMS based. The other way around I can send it an SMS with a code and command, commands include many options, most top secret... but asking it for a position report is one. The old test routines, that can be used in a script, are here:

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I think some of that code is in the xgpspc release, that is a very old release:

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Because there is not always cellphone coverage in remote harbours the boat can send voice messages via PRM or if you are licensed radio-ham via 70 cm (Uses a Baofeng porto). Have not implemented voice commands to the boat yet.....

*

Reply to
Jan Panteltje

Whether you can access the LAN without the click-thru authorization depends on how it's implemented. In every place I've seen, like Starbucks etc, I can identify the gateway with IPCONFIG but I can't even ping the gateway before the click-thru. Maybe you can if you're going through a switch separate from the gateway.

Reply to
Tom Del Rosso

how about an ESP8266 in access point mode, have people logon to the wifi and access a web page to open the door

Reply to
Lasse Langwadt Christensen

That's a great way to be fined by the FCC, and spend time in Federal prison.

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Reply to
Michael A. Terrell

He didn't know what they wanted it for. It's those damn unions.

Reply to
Tom Del Rosso

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