Topics Topics Edit Profile Profile Help/Instructions Help Member List Member List  
Search Last 1|3|7 Days Search Search Tree View Tree View  

RF alarm signal indicator

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 04 January, 2013 » RF alarm signal indicator « Previous Next »

  Thread Last Poster Posts Pages Last Post
  ClosedClosed: New threads not accepted on this page        

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

plebas
Just joined
Username: plebas

Post Number: 4
Registered: 11-2012

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 03 January, 2013 - 03:02 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi,

About six weeks ago some of you were kind enough to respond to my plea for help in a thread with the same name as above. In case you're interested I have attached the original message below, and I attach here the circuits I have actually built and got working!

I eventually discovered a source of mains power (in the room below the "bell room" in the Tudor tower), from where I have fed a long lead via a 9V mains adapter. I also found that the alarm flashing light does not seem to be operational, so I now simply use a noise detector instead of a photodiode to detect the alarm. The transmitter sends of short pulse of RF every 10 seconds with the current status of the "noise" (extended by a 10 second monostable) encoded into it. The receiver output simply consists of two LEDs, one to indicate the pulses of RF received and the other to indicate noise being detected. The noise could of course be either the alarm or the ringing of the church bells, or some other noise. But the LED is only to confirm what we can already hear from the vicarage, so this is not a problem!

Anyway, if some of the circuit components look a little unusual, they are simply ones had to hand. I don't think any of them are particularly critical. I did have to do a little experimentation with the (electret) microphone and op amp feedback resistor. But I'm glad to say the whole setup does seem to work now. Thanks again for all your ideas!!




Hi,

Does anyone know of a circuit to do the following? I'm looking to construct an RF transmitter and receiver to carry a signal indicating a burglar alarm is sounding 100 metres away.

I live in a vicarage 100 metres away (as the crow flies, according to Google maps, with a line of trees blocking line of sight) from the church. My wife is the vicar, and we can hear when the burglar alarm in the church sounds, but it is often difficult to distinguish it from other car alarms etc. This results in trekking through the cold, often in the middle of the night, only to discover that it's someone else's problem, not ours!

I do not have access to the alarm itself - positioned at the top of a Tudor tower with a long spiral staircase to reach it - without voiding the warranty. I have tried accessing the electrical signal from the control box at the bottom of the tower by wrapping a wire connected to a FET around the connecting wire. However, the current seems to be too weak. The alarm box does flash a bright (blue) light when sounding, and so I was thinking of using a photodiode as the input transducer. The problem is that there is no easy electrical supply at the top of the tower, so the transmitter will have to be battery powered with a very low current to avoid having to change the batteries too often, it being so inaccessible. It's also very cold and damp up there! The output from the receiver needs just to be an LED or a buzzer.

Any ideas?

application/pdfRF Alarm Transmitter circuit
Alarm Transmitter 2.pdf (19.5 k)
application/pdfRF Alarm Receiver circuit
Alarm Receiver.pdf (15.3 k)
Top of pagePrevious messageNext messageBottom of page Link to this message

alec_t
Frequent Contributor
Username: alec_t

Post Number: 788
Registered: 03-2009

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 03 January, 2013 - 07:39 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Good to know you got it all working.
Top of pagePrevious messageNext messageBottom of page Link to this message

mikeb
Frequent Contributor
Username: mikeb

Post Number: 777
Registered: 02-2008

Rating: N/A
Votes: 0 (Vote!)

Posted on Thursday, 03 January, 2013 - 10:36 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

nice job

Administration Administration Log Out Log Out   Previous Page Previous Page Next Page Next Page