door alarm

Posted on Feb 6, 2014

Another way other than magnetic reed switches for the alarm trip switch. The circuit needs the switch to be normally closed / held open (when the door is shut. ). I was looking to use a normally closed momentary push button. Another thought was trying to make a DIY magnetic switch myself. Are there any ideas that anyone else has to make a passive door alarm switch You could feed your circuit from an inverter.

door alarm
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I`m not sure how you would go about making a momentary reed switch. The last switch I had was just like yours, it was disassemble though not sure if yours is. You could probably covert it to a NC if you bend the metal strip inside just right. I pulled a magnet from a tiny speaker. I was thinking that a thin strip of metal lying accross a two screws attached at one end shorting them together. When the magnet (on the door) gets close one end of the metal strip would lift off one of the screws breaking the circuit. I`m not sure if I can get that to work though. Your custom made NC switch should work if you can get the metal bent just right. An inverter is a very basic digital IC. If you input a high voltage it outputs low and vice versa, so it will invert the signal coming from your switch, making it look like a NC switch. Depends on what voltages you`re running at and what you`re switching because inverters don`t generally pass as much current as a switch can, if it`s just a signal though it would work fine. The switch makes or brakes 9 to 12 volts feeding a two tone siren circuit I made using two NE555 timer IC`s. (UK siren) I can use another relay if I want the switch to be normally open but I don`t think that makes the switch mechanizm design any easier to accomplish. The first is the siren circuit I used and the other is the delay to enter timer circuit, set for 30 seconds. I`ve added two more relays to the circuit. One...

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